replacing a c-4 fuel pump


Staff member
keep in mind fuel pumps and the wiring are not running constantly and sloshing fuel tends to keep the components cool,
Id also point out keeping your fuel tank at least 1/3-1/4 full and throwing 4-5 oz of marvel mystery oil into each full fuel tank, is a proven way to increase fuel pump durability, no one would reasonably dispute the wisdom of replacing the O.E.M. wiring with stranded 10 ga to reduce the ohms resistance to allow a bigger amp load electric fuel pump , but that is not a mandatory upgrade, with most of the higher flow rate in tank electric fuel pumps, its just a smarter route to take, as it provides a larger safety margin, in that theres hundreds of guys running higher amp fuel tank pumps that have not had issues

after the first few mods I did to my 1985 corvette (swapping to a 11:1 compression 383, short block, ported trickflow twisted wedge heads and swapping in a crower 00471 roller cam) it ran like crap, because the OEM 24 lb injectors could not keep up with the demand for fuel at much over about 4000 rpm, even with the stock TPI intake in place, and the stock fuel pump would supply about 40 psi at idle but by 4000 rpm pressure dropped to only about 35 psi.

340 lph-90 gph that easily support 650-700 hp
obviously larger than stock flow rate injectors will be required
most systems would be set to run 80% max injector pulse ,
so you could in theory support up to 8 52 lb injectors,
but something closer to 600 hp and 48 lb injectors ,
would be more reasonable as a goal

installing ADJUSTABLE EFI fuel pressure regulators, which are a darn good idea on the older C4 corvettes

450 lph-119 gph that easily support 950 hp
obviously larger than stock flow rate injectors will be required
most systems would be set to run 80% max injector pulse ,
so you could in theory support up to 8 66 lb injectors,
but something closer to 600 hp and 64 lb injectors ,
would be more reasonable as a goal

and btw the stock OEM wiring, for the in tank fuel pump, works just fine with the 450LPH aftermarket fuel pump.

in an ideal world all the automotive wiring would be significantly larger gauge than it generally is,
and the fuel lines would be AN#8 (1/2") vs AN#6 (3/8")
but I've had no issues installing several electric aftermarket fuel pumps,
using the existing wire harness in c4 corvettes,
obviously if you have the time and skills upgrading the wire gauge feeding the pump to 12 ga or 10 ga wire,
would reduce the resistance ,
but its not proven to be a weak point so far.

keep in mind fuel pumps and the wiring are not running constantly and sloshing fuel tends to keep the components cool,
Id also point out keeping your fuel tank at least 1/3-1/4 full and throwing 4-5 oz of marvel mystery oil into each full fuel tank, is a proven way to increase fuel pump durability




no that slightly larger capacity fuel , pump will work ok, in a stock or modified c4 corvette, keep in mind the pump provides fuel flow, the fuel pressure regulator provides a resistance too that flow, the restriction to flow provides back pressure, if the pump can provide a slightly higher flow than stock it simply has to work less and has slightly less chance of over heating or wear issues.
my 1996 corvette had a significantly higher flow capacity in tank fuel pump for several year's plus and it runs much better than it ever did with the stock pump. btw,be sure you install pump pre-filter, that as it keeps micro trash out of the fuel pump

its a soft flexible micro filter, that comes with the fuel pump, that easily fits into the tank, upper opening, , its an in tank fuel permeable screen that easily bends and returns to its intended size & shape, not an issue


[ "ecss"]The fuel pump relay will be enabled by the ECM when you turn the ignition On for
about 2 seconds. It will also enable the relay if it sees distributor reference pulses
which indicates the distributor is rotating either because the engine is cranking
by the starter or the engine is running.think logically, take it step-by-step!
you really need a shop manual for YOUR YEAR CORVETTE.
the most important and effective performance asset you have is simply your ability to ask yourself questions, the ability to think logically isolate and test components carefully and doing the research if its required to find the best answer's you'll need.

first verify the fuel pump is getting the voltage it requires, get out a multi meter and use the link above, if the pumps ARE bad theres a very good chance the fuel in the tank is contaminated with alcohol,rust or water and you need an in tank pre-filter
a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful
never assume a damn thing ISOLATE ,TEST AND VERIFY



If you have 12 volts on pin A of the relay that 12 volts goes to the FP fuse and
then the 12 volts goes to the fuel pump. chart index.htm




If you want to test the fuel pump manually, you can apply 12 volts direct to pin G on the
diagnostic connector above the drivers right knee. The 12 volts goes thru the
normally closed contacts of the fuel pump relay to the fuel pump fuse and then
to the fuel pump motor.


where is fuel pump test terminal on 1996 corvette located??

GM replacement sending unit. ACDelco part FLS1099



The fuel pump should turn on and stay running.

Here's the schematic, of a 1995 corvette fuel pump control. posted below,
save it and print it out.

There are two sources to power the fuel pump.
The PCM enables fuel pump relay #1
As long as the engine is running or cranking.
Otherwise when you turn the ignition on it only enables the relay to provide the fuel pump power for a couple of seconds,

Other source is if the oil pressure switch located next to the rear of the intake ,if the oil pressure is above around 3 psi, 12 volts from fuse ECM Fuse#1
will provide 12 volts to the FP1 fuse#14 which goes to the fuel pump connector Gray wire.

Fuel pump relay #1 is located along the passenger side front edge of the dash. All of the relays
are the same so you can swap them around. Fuel pump relay #2 is used for the LT5 so it
may not be there.

Posted by Hooked on Vettes
Here's the schematic for a 95. I'd think 96 would be the same.

The fuel pump relay is located under the passenger side front edge of the dash. There should be 5 relays.

Relay A for the Horn
Relay B for Fuel Pump #1
Relay C Probably not used. (In 95 used for ZR1 2nd fuel pump)
Relay D for Fog Lamp
Relay E for Courtesy Lamp
Socket F empty not used

The relays on the passenger side wheel well are for the AC Clutch,
and High/Low blower speed relays if you have manual AC (C60).


FUEL LINE SIZE Fuel line size is determined by the horsepower of the engine. Up to 350 HP 5/16" or 4AN Up to 500 HP 3/8" or 6AN Up to 700 HP 1/2" or 8AN Up to 1200 HP 5/8" or 10AN RETURN LINE SIZE Return line size is determined by the output of the fuel pump. Up to *29 gal/hr (110 liters/hr) 1/4" or 3AN Up to *45 gal/hr (170 liters/hr) 5/16" or 4AN Up to *90 gal/hr (340 liters/hr) 3/8" or 6AN Up to *180 gal/hr (680 liters/hr) 1/2" or 8AN *Pump output @ 45psi PUMP SIZE Pump size is determined by the horsepower of the engine. Horsepower x .083 = gallons per hour @ 45 psi Example: 500hp x .083 = 42 gal/hr or Horsepower x .314 = liters per hour @ 45 psi Example: 500hp x .314 = 157 liters/hr NOTE: add 25% to pump size for supercharged applications.



I bought and have used the BOSCH PUMP, but theres better options available now than there were 12 years ago, ID suggest a 300-350 lph pump with AN#8 lines , and fuel filter on an engine that is intended to produce north of 500hp,
A common upgrade that frequently works on C4 corvettes but its marginal on a serious race engine in my experience, especially if used with stock fuel lines and filter.
heres a pump I find works well with AN#8 lines and filters

Bosch High Pressure Pump in the tank replacement fuel pump in my 1985 vette when the original pump failed, and yes after helping others install the cheaper knock-offs I think theres a difference in quality,and while the price is higher and there are other options, I would at least consider the better brand name pumps, rather than the less expensive knock-offs.
if you look at places that sell BOTH good quality and bargain priced parts like ROCKAUTO or SUMMIT OR JEGS, youll see theres fuel pumps available from under $30 to over $250 PLUS aftermarket sources can go up from there, theres no way that a fuel pump from a well known manufacturer like lets say BOSCH aeromotiveinc or WELBRO that sells for 8 times what the bargain basement pump is going to be made to the same quality or contain the same attention to detail or have similar component quality, you tend to get what you pay for

efisystem.jpg ... gnosis.pdf ... _Pump.html


first check your shop manual for the fuse and fuse able link locations
fuses are located in several locations and fuse-able links near the battery

Bosch High Pressure Pump 0-580-254-984

Rated at 44 GPH @ 90 PSI 750+ Hp This pump is identical to the Accel part number 74702 which they boast will handle 870 Hp! ... _pumps.htm



the fuel pump has a 12 volt 15 AMP fused circuit


Under the hood--to the right of the blower motor---should be 2 relays---fuel pump is the one farthest to the right.

theres a good deal of good and useful advise, in this thread but Id point out the
sensor(s) next to the distributor, base ,could be a cause of a problem, because occasionally one of these starts acting up intermittently causing the fuel pump or ECM to stop working,or the VATS system, or the FUEL SUPPLY SYSTEM.




heres some other possibility,s ... gnosis.pdf injection ecm pinouts.htm

read thru these threads also, as theres a good deal more related info in those threads and links

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers
The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch.
(If the fuel pump relay fails, you can still normally get the car to start and run unless you can,t make at least 4 PSI oil pressure. This is a limp home mode feature put in place to allow for a fuel pump relay failure).

viewtopic.php?f=32&t=596 ... post129791

its not necessary to drain the tank but its a good idea to do so.
IT IS NECESSARY TO DISCONNECT THE BATTERY READ THAT AS ABSOLUTELY MANDATORY during the swap procedure to prevent any chance of accidental problems

step one have the parts on hand PLUS 3 ft of 3/8" fuel line and 1 ft of 5/16" fuel line , I know, you may not need the fuel line but in many cases its faster and easier to remove the old line and replace with new ones
hose clamps, youll want several 1/2" size for the lines

fuel pump

fuel pump screen

fuel filter
(optional but a GREAT IDEA)

ok, step one,
make darn sure the keys are out of the car and the battery is disconnected for extra safety

step two, open the fuel fill door center rear deck where you normally fill the car and remove the gas cap

step three
remove the four very small torx screws in the corners and lift off the door assembly

step four
theres a rubber bib fuel spill tray)(around the fill spout, remove the gas cap and work the bib fuel spill tray ) (out , and disconnect the water drain line and label it with masking tape/pen

step five
label the three lines with masking tape/pen (upper line/lower line /left side line)
remove each at the central point in the opening, then disconnect the electrical connector on the lower edge of the opening

step six
remove the 8 10mm bolts and look carefully at where the components go, after they are removed the pump lifts up and out, the pump normally comes with instructions also, but its fairly simple, the pump, lines and fuel level sensor lifts out as a sub assembly, look thru the link below for pictures and more info
the stock pump puts out less than 60 gallons an hour

AEI-11140_IT.jpg ... uel-pumps/
340 liters per hour flow should be good for/ approximately 700HP (thats approximately 90 gallons an hour

just a bit of related info that may or may not apply in your case, electric in tank fuel pumps are COOLED by both sloshing fuel and fuel flow rates and are DESIGNED to be used with a return style fuel pressure regulator, use with a nearly empty fuel tank or with a dead head style fuel pressure regulator will DRASTICALLY reduce the pumps life expectancy ... And_Wiring
heres a 200 gallon an hour rated pump that should easily supply over 1000hp, but youll need AN#8 or larger fuel lines
201gphelpump.jpg ... _guide.pdf


the fuel pump has a 12 volt 15 AMP fused circuit



"I have replaced countless in tank fuel pumps. In tank fuel pumps are submerged in fuel in order to help them run cooler. I see many people out there (especially with today's gas prices) who run their vehicles on the empty side of the tank. Empty tank=hot pump. It's just as easy to keep the top half filled as the bottom half. Keeping adequate gas in the tank in conjunction with a regular filter change will insure your pump will last it's longest."

255 liters per hour flow should be good for/ approximately 500HP
access to the fuel pump is thru the panel around the tank fill cap SIMILAR TO THIS, held in place with 10mm bolts in this picture
label the fuel return lines before you disconnect them to insure replacing them correctly

Fuel Pump




In a C4 Corvette, the fuel pump is one of those crossover items that is part of both the electrical system and the fuel system. The pump is a submerged variety, electrically operated, contained in the fuel tank and somewhat difficult to get to.

Although the pump is difficult to physically check, you can make certain that it at least runs by turning the ignition switch to on (but don't start the engine).

If the pump motor is working, you will hear a whirring noise coming from from the rear of the vehicle that will last for 2 seconds. Note that this does not prove that the pump is actually pumping fuel in sufficient quantity and/or pressure but it does prove if the pump motor itself is operating.

If you do not hear any sound, check the fuse labeled "Crank" on the fuse panel.

If the fuse is not blown but there is no sound from the tank area, there is a problem with either the motor or the wiring feeding the fuel pump motor.

If the pump appears to be working, you will need to measure the fuel pressure at the Shraeder valve located on the fuel rail on the engine. Anything below 35 PSI is cause for alarm and can be the fuel pump (pumps---2 each---on a ZR-1), the fuel pressure regulator, the check valves in the fuel return line, the fuel filter or a obstructed fuel line.

Once you have troubleshooted your Corvette’s Fuel System and determined it is time to install a new fuel pump & sending unit on your Corvette you will first need to disconnect the negative battery cable and relieve the pressure in the fuel system. To relieve the fuel system pressure on a C4 Corvette you can simply remove the gas cap and let the car sit for 15 minutes. Once the pressure is relieved drain your Corvette’s fuel tank and remove the tank filler door attaching screws and bezel. Next, lift the fuel tank filler pipe housing and disconnect the drain hose from the nipple. Before disconnecting the fuel tank filler pipe housing, clean all fuel connections and surrounding areas to avoid contaminating the fuel system. Next disconnect the fuel hoses and EVAP hose from the fuel sender assembly. Plug or pinch the fuel feed and return hoses and remove the fuel sender electrical connector. To finish removal of your C4 Corvette’s fuel pump and sending unit remove the fuel sender assembly attaching screws, assembly, and gasket. You can re-install the old gasket but first check to see if your new C4 Corvette Sending Unit came with a new gasket. If it did then discard the gasket and thoroughly clean the gasket sealing surfaces. If you just purchased a new C4 Corvette Fuel Pump you will need to purchase a gasket separately or re-install the old gasket. Finally, cuts, nicks, swelling, or distortion is common on the fuel feed, fuel return and EVAP hoses so be sure to inspect these hoses before proceeding.

Once you are ready to install your new C4 Corvette Fuel Pump & Sending Unit begin by positioning the gasket on the fuel tank with the notch facing forward in the right hand corner of the tank. Carefully fold the strainer to allow it to fit through the opening in the tank. Next, install the fuel sender assembly into the fuel tank and re-connect the fuel sender electrical connector. Then connect the EVAP hose and tighten the hose clamps. Re-connect the fuel drain hose to the nipple on the filler pipe housing and place the housing around the filler pipe. Now you can re-install the filler door bezel, add fuel, and re-connect the negative battery cable. Before driving your Corvette away, be sure to turn the ignition switch on, off, then back on and check for any possible fuel leaks. If no leaks are recognized your Corvette fuel pump replacement was a success.

the answer to how big a fuel pump yoou need or what injector size is required or what fuel pressure level will be necessary is a predicable value and it depends on what power range your dealing with and what your trying to supply with fuel and the rate its potentially using that fuel, the stock fuel pump will easily supply 400hp plus on a c4 corvette or a bit more and the stock injector size won,t
it takes (X) amount of fuel/air mix at about a 13:1-14:1 ratio being burned per minute to make (Y) amount of HORSEPOWER
you can spin a small engine fast or a big engine slower but it will take a certain amount of fuel being consumed to produce a power level and its reasonably predictable at about a BSFC of about .5-.55, you might be amazed at what you can learn reading thru the linked info on the site.

the fuel filters located under the front pass side door area near the frame and the shop manual will go into some detail on its removal, yes your going to loose some fuel so its best to do this up on a lift or jack stands where access is easier and where you can see what your doing.
theres an arrow on the filter indicating direction of fuel flow for a reason , pay attention and do it correctly, have some shop towels and a fire extinguisher handy ANYTIME you work on fuel lines!
Fuel System

The TPI Fuel System comprises the following components:

  • Fuel Tank
  • Fuel Pump
  • Fuel Pressure Regulator
  • Fuel Lines
Fuel Pump
In the original GM applications, the fuel injection pressure pump is installed inside the vehicles fuel tank. Adapting this pump has never seemed to us a practical solution, unless you are installing the TPI system on a vehicle that utilises the stock GM gasoline tank. This would allow for the installation of an internal tank type pump. If you are installing the TPI system into a vehicle that was originally equipped with carburettors, or even a throttle body fuel injection system, it WILL be necessary to install a compatible high pressure port fuel-injection type pump. Any number of fuel pumps will serve the purpose. We can recommend the fuel pump from a 78-80 and 82-85 Datsun 280Z. The Nissan part number for this pump is 17011-P7211. In addition, these pumps are usually readily available from wrecking yards, as are similar units from BMW, Mercedes Benz, Jaguar and many other late-model port-injected vehicles.

The electric fuel pump used should be capable of maintaining at least 50 psi under full throttle, and a return line MUST be plumbed back to the fuel tank/tanks if there is not one installed on the car!

By installing the appropriate size tee-fitting into the fuel supply line from the tank to the inlet side of the fuel pump and connecting the return line into this suction line at the newly installed tee, the need for a return line can be met without removing and modifying the fuel tank.

If you are installing your TPI system in a vehicle which was originally equipped with a carburetted engine and a mechanical fuel pump that was equipped with a factory installed return line, BE AWARE, that many of these systems have a restriction in the return line. This restriction should be removed to eliminate the possibility of unnecessarily high pressures in this portion of the fuel system. These restrictions are often contained in the return line fitting on the gas tank sending unit mounting flange. If it is inconvenient to access this flange to remove the restriction, the return line can be re-routed to the fuel pump inlet line, as described above.

Fuel Regulator
A fuel pressure regulator is mounted on the rear of the right side of the TPI fuel rail. This non-adjustable regulator controls fuel pressure, to maintain it at about 41 psi under high vacuum conditions, such as idle, and up to 47 psi under low vacuum conditions, such as full throttle operation. Adjustable fuel pressure regulators are available through a number of after-market suppliers, for high performance applications.

Fuel Lines
Because of the high fuel pressures involved, we prefer to use braided stainless fuel lines with threaded connectors, as opposed to just using hose clamps and rubber hose, when making the connection between the TPI unit and the fuel pump! The pressure inlet of the TPI system is the fitting with the larger I.D. A return line MUST be connected from the petrol tank to the smaller I.D. fitting. If you are utilising braided stainless hose and fittings, it will be necessary to purchase after-market adaptor fittings which thread into the hose connections, or the TPI manifold, to allow the use of these improved hose and fitting assemblies, since the OEM connections utilise metric threads and O-ring type seals. These adaptor fittings are available, either in a male configuration for installation into the fittings on the fuel rails of the TPI or, into the ends of the stock rubber hoses which attach to the body/frame mounted steel fuel lines that come forward from the fuel tank, or in a female configuration, for installation onto the end of the engine mounted steel tubing extensions, which are a part of all factory TPI fuel line installations.

The above-mentioned items are all that could be considered separate elements of which are component parts of the TPI installation. Simply stated, the system will not work at its designed level of performance if any one of the above items is deleted! The following information will include some additional items which, while not required to make the system functional, are items that are utilised in the factory installation to make everything work as originally designed, and which may be used, as necessary, or deleted if so desired, with no functional effect on the real world operation of the unit. injection troubleshooting page C.htm
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Without wasting my stock pump, should I replace it with a high flow pump? I just went to a 383 strocker and 30lb injectors, adj fuel press reg, TPIS big mouth manifold, Super ram and runners, Dart heads. The car idles nice now and feels strong, will I see any difference or will I be wasting money? John at FIC said the stock pump would be fine.
sdhd97 said:

Without wasting my stock pump, should I replace it with a high flow pump? I just went to a 383 strocker and 30lb injectors, adj fuel press reg, TPIS big mouth manifold, Super ram and runners, Dart heads. The car idles nice now and feels strong, will I see any difference or will I be wasting money? John at FIC said the stock pump would be fine.
in most cases the stock fuel pumps able to supply the needs up to about 500hp, on a dyno, but under the inertial loads of racing,
its marginal and working at or really beyond , its flow limits, and even a partly clogged fuel filter, or less than 1/4 tank of fuel will frequently reduce flow, and cause problems with the engine leaning out or detonation issues

these diagrams may help at times


grounds1.jpg ... A-009H&eq=

Walbro 190L/Hr Pump
Filter sock - 30 micron filtering (factory=70 micron)
Walbro to GM direct power wiring (no adapters)
Terminal lock
High pressure fuel line
Stainless gear clamps
Rubber pump mount
Pump sound insulation sleeve
C4 fuel tank gasket
Stainless hex-head tank bolts, washers and o-ring seals ( 9 pieces)
Hex key
Silicone grease

The Pump

Walbro sets set the industry standard in high-performance in-tank pumps. Walbro pumps are used as factory equipment in performance vehicles such as the C5 Corvette. Walbro's gerotor design is able to maintain high volume at elevated pressures. This is done by squeezing the fuel out between two gears instead of pushing it like most factory vane pumps. The positive displacement gerotor design makes high-performance Walbro pumps small, light weight, quiet, efficient and reliable. Racetronix offers the FPA-009 bundled with the GSS242M 190L/Hr pump or this kit bundled with the GSS340M 255L/Hr pump in this kit. The GSS242M is capable of supporting approximately 450RWHP* @ 13.5V through factory lines. The GSS340M is capable of supporting approximately 550RWHP* @ 13.5V through factory lines. (* HP numbers will vary based on engine and driveline efficiency, operating pressure and pump voltage.)

Why do other vendors offer the GSS307M but Racetronix does not? Racetronix has decided to bundle the GSS340M pump with all C44 HP systems as it will do everything the GSS307M will do and more regardless if you are running a naturally aspirated or forced induction motor. Running a high-pressure capable GSS340M pump does not cause abnormally high fuel pressure. Fuel pressure is controlled by the regulator on the fuel rail. The GSS340M's motor design allows it to draw less power than a GSS307M at the same operating pressure. The pressure setting of the GSS340M's internal safety bypass valve is set higher than the GSS307M's to accommodate forced induction applications which require higher fuel pressures than naturally aspirated motors. The Walbro GSS340M is only a few dollars more than the GSS307.

Other vendors state that the GSS340M is a discontinued pump? Walbro introduced the F20000169 pump to replace the GSS340M in March 2004. The F20000169 is exactly the same pump internally as the GSS340(M) apart from the new smaller offset molded inlet. This new inlet design means that Walbro no longer has to machine the ends of a GSS340 pump in order to accept a GM style filter sock. The F20000169 is more expensive than the GSS340M therefore Racetronix will continue to offer the GSS340M while passing the savings along to our customers. Please note the 'M' in GSS340M stands for machined end. A GSS340 (not machined) is the typical pump used in vehicles such as a Mustang and will not accept the GM style filter sock nor fit a G.M. fuel pump module properly. The GSS340 is still a current production Walbro pump.

Pump Installation kit- Racetronix Exclusive!

Walbro does not manufacture a fuel pump installation kit specifically for the C4 Corvette. Walbro's 400-835 and 400-1016 fuel pump installation kits which are normally bundled with the GSS340M and F20000169 pumps are tailored towards 1980's g-body and b-body fuel senders. Racetronix has bundled together a C4 specific fuel pump installation kit which includes a few upgrades such as a sound insulation sleeve, one-piece teflon in-tank wiring harness, C4 tank gasket and stainless sender bolts with o-rings. The factory pump came with a sound insulation sleeve so we have included one. This sleeve helps reduce pump noise heard from outside the tank. Racetronix has manufactured a quality C4 tank gasket and bundled it with new stainless steel tank bolts and o-rings. Most C4 tank gaskets are in pretty bad shape and will not provide a proper vapor seal. The factory black-oxide sender bolts are typically rusted and their o-rings have deteriorated. These bolts must be in good condition and their o-rings intact to achieve a vapor seal as they extend into the gas tank. GM fuel sender gasket (P/N 25091503) lists at $15.25. The fuel sender bolts with o-rings (P/N 14044556) list at $45.54 for a set of nine. A total value of $60.79 included at no extra charge. Racetronix supplied bolts and tank gasket are made from superior materials. A hex key is included to aid in the installation of the stainless sender bolts.

In-tank Wiring - Racetronix Exclusive!

In-tank wiring is quickly becoming a major problem due to the age of the C4's. Many terminals are heavily corroded or rusting off.
The generic in-tank wiring adapters supplied with other installation kits rely on the questionable factory wiring and adds another connection to the equation. This translates to more resistance / voltage loss and an extra potential failure point.

Racetronix in-house harness manufacturing facility has produced a one-piece replacement for the in-tank pump wiring. Racetronix replacement in-tank wiring plugs directly into the new pump and into the factory bulkhead connector thereby eliminating all the factory pump wiring and the need for in-line plug adapters. The Racetronix harness is made from mil. spec. silver plated 14 gauge Teflon wire vs. the factory's 16 gauge Teflon wire. Teflon is the most resistant to gas and solvents. All connections are assembled using our computerized crimp-quality monitoring system and then circuit checked for the utmost in reliability. There are no wires to cut, crimp or splice. All connections are Plug & Play.

no one anywhere can accurately predict exactly what your particular engine combo will find to be the best tune-up specs but any good dyno operation or experienced shop will start with a basic known base line and tweak the combo to get the best results, you'll want a consistent 40 lbs of fuel pressure, you'll want to keep the coolant temps under 200 F
youll want the oil temps in the 200F-210F range
and youll ant the injector pulse duration to stay under 75%-80% at peak rpms , this may require larger injectors, and youll want significantly less than 3 psi of exhaust back pressure at peak rpms.
heres a basic tune


installing a fuel pressure gauge on your LT1 fuel rail will help provide a slightly higher fuel flow from existing injectors

an adjustable fuel pressure regulator allows you the option of feeding the injectors with more pressure which results in a slightly richer fuel/air ratio at any pulse duration.(at times this helps during a tune up)



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Thanks Grumpy, I'm going to spend my money on new shocks and brakes. I'm going to order from Vette Brakes..

fuel_pump_circuit 2.JPG

fuel_pump_circuit 1990-92 730.JPG

fuel_pump_circuit 1991-92 727.JPG

"I think some people might be mis-understaning this FP circuit.




The only purpose of the FP relay is to give power to the FP when you FIRST START the car, after the car is running the oil pressure comes up and CLOSES the oil pressure switch which is in series with the fuel pump. This oil pressure switch is a SAFETY to keep the car from running when there is NO oil pressure (or atleast not enough to keep the OIL Pressure switch from closing whatever that value may be).

Here is how it works... There will be 12vdc+ sitting at terminal E of the FP relay at all times. When you put the key in the ignition and turn it to the start position 12vdc+ is sent from the ECM (terminal A1) to the coil of FP relay (term C)which energizes that relay and closes contacts on the FP relay terminals A to E and that gives the 12vdc+ sitting on FP relay terminal E (remember term E is hot at all times) a place to go...across E to A then to the fuel pump (assuming FP Fuse is good). Then sometime after that (i would have to hunt that time period up in the FSM) the relay deenergizes. But that doesnt kill the power to the FP because remember the engine is running and your oil pressure has come up and closed the oil pressure switch. Now power for the fuel pump is coming from the fusible LINK across the closed oil pressure switch and across the Fuel Pump fuse to the fuel pump. Now if you lose oil pressure the fuel pump will shutoff and the engine will die. (out of gas).
So you see the FP relay cannot be used for anything other than starting the car up....otherwise you would not have the advantage of the oil pressure switch safety circuit for loss of oil pressure. If the oil pressure safety switch opened because of loss of oil pressure and your FP relay were powering the fuel pump the oil pressure safety switch would not kill the engine upon loss of oil pressure because the FP Relay would be powering it also at the same time.

Dont confuse oil pressure safety switch with oil pressure sending unit. The sending unit is used to tell your oil pressure gauge how much oil pressure there is (PSI).

So you see the FP Relay is kind of a misnomer. It is not used while the car is being driven. You are running on the oil pressure switch during that time. "

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"On our way to Bloomington Gold in 2011, the fuel pump in our '95 coupe crapped out. My quick and dirty troubleshooting on the side of the road revealed no telltale sound of the pump when the key was in RUN, and the engine wouldn't run in START either. I deduced that it was probably the pump.

The car was returned via flat bed to NW Illinois from DeKalb - an less than fun experience, as well as an expensive one. When I got the car home, I confirmed my initial diagnosis by verifying that I was getting battery voltage when the key was in RUN (2 - 3 seconds), and then battery voltage again when the key was in START. I thought about putting 12 Vdc directly to the pump, but didn't have a power supply handy.

I ordered the Racetronix FPA-010 Fuel Pump kit. This includes the Walbro pump as well as a handy installation kit (tank gasket, in tank wiring harness, and new bolts w/o-rings, as well as a variety of small parts). I had all the parts I needed by Friday, and started on the project Saturday morning. I was done by 11 AM, including breaks and other diversions.

Here are the steps to follow for this installation:

1. Remove the gas door and hard plastic cover. There are four Torx screws that secure it to the car.

2. Now remove the rubber overfill/drain. This exposes the top of the tank and the evaporative emissions, fuel delivery, and fuel return hoses. You can also see the nine bolts that will need to come out.


Gas door & overfill/drain

3. Remove the fuel pump/gas gauge connector from the harness (not the top of the fuel tank). There is a small gray locking mechanism that needs to be squeezed (gently!) and lifted up so that the connector will come apart.

4. This step was the WORST part of the project for me. I had the devil's own time getting the hoses off the fittings. Eventually, however, I prevailed, and the hoses were removed.


5. Remove the nine bolts, and the entire sending unit/fuel pump assembly lifts out. You have to turn and twist things a bit to get it all clear, but it's simple. Note that there is probably still residual gas in the lines, so be careful. I discovered that when I got mine to the bench, and turned it over - and gas poured out of the line ... :WTF


Fuel Pump & sending unit

6. I disconnected the wiring from the old pump, and slightly moved the lower locating bracket, and then pushed the pulsator up on the fuel line just a bit. That gave the old pump clearance, and it came out of the bracket. I removed the pulsator from the system, as the new pump doesn't require it.

7. The original wiring harness is disassembled by removing the two fuel sending unit connections (purple signal wire and black ground wire) and the bulkhead connector. The sending unit connections are easy to pry off with a small pair of pliers (slowly and gently). The bulkhead connector has an orange lock that needs to be removed, then it is released by pushing (steadily) on a plastic retainer in the middle of the ground terminal of the connector.


Old Wiring

8. I then dry fit the new pump with the new bottom mounting grommet so I could see how much to trim the short fuel line that replaces the OEM pulsator. I used about 1 - 1.5" of line.

9. I then put the hose clamps on the steel line, coated the end of it with a bit of dielectric grease, and put a spot on the fuel pump. I slid the hose on the line, a bit past where I needed it, and then (after putting the sound insulator and grommet on) slid the new pump into the fuel line, and then lined it up with the bracket. I put the clamps in position and tightened them up, and confirmed that the pump was secure between the fuel line and the grommet. I then installed the new 30 micro tank filter as supplied in the new kit.


New Fuel Pump Installed

10. I routed the new harness to the fuel sender, the pump, and then the bulkhead. I discovered that the ground lead is slightly different than the factory design, and doesn't have quite enough wire to go over the fuel lines, so I went between them. Once I did that, I remembered to put the orange lock back in the bulkhead connector (hate it when connections open up because I forgot something!), and checked wiring one more time.




11. I put a very light coat of dielectric grease on the tank gasket, and it fit very nicely on the tank. The notch in the gasket goes in the upper right corner as you look down on it - and it's rather obvious if you get it wrong, because the nine bolt holes are asymmetric.

12. That done, I put a light coat of dielectric grease on the mating surface of the sending unit/fuel pump assembly, and installed it back in the tank. Again, it isn't hard - but you have to move it around a bit as you're installing it (and be mindful of that gasket!). Once it was back in, I used a small screwdriver to line up the nine bolt holes.

13. I installed eight of the nine new screws, and used one hold screw (with a new o-ring) due to some apparent factory thread problems. I had damaged threads on one bolt, and the new bolt didn't want to thread. Old bolt ... no problem. I put a small amount of dielectric grease on each bolt as a lubricant and to assist the o-ring seal.

14. Reinstalled hoses (after applying a dab of dielectric grease on the fittings) and tightened. Did a once over to verify that everything was mechanically sound, and then remembered to CONNECT THE POWER LEAD BACK TO THE FUEL PUMP CONNECTOR!!! Put connector back together, and remembered to reinstall small gray lock.

15. I put the gas cap on, and went to get the keys. Came back out, turned key to RUN, and HEARD NOTHING!!! Muttered 'screw it!' to myself, and cranked it ... and IT STARTED!

16. I let it run a few seconds (more than 15, less than 45), and shut it down. Turned key to RUN, and heard the reassuring sound of the pump running for a couple of seconds. Car started right up, so I pulled it into the driveway, and ran a few sprints up it!

17. Reinstalled the overfill/drain (don't forget to connect the overfill tube!) and the gas door.

Car runs great, and other than missing Bloomington and the cost of the flat bed ride, this was a fun project.


Miscellaneous Pictures:

Racetronix Kit

Old Pump vs New Pump

Taped off Gas Tank - Don't Want to Build up Vapors!
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one of the most common mistakes less than experienced performance enthusiasts, face and very commonly over-look, is the fact that the internal cross sectional area on many hydraulic and fuel line fittings are considerably more restrictive to flow that the fuel limes or hydraulic lines inside diameter they were designed to be used with, and it varies a great deal between different manufacturers, now ideally the fittings internal passage cross sectional area is both consistent and the same or greater that the tube or hydraulic line size, it listed to match, , so a 1/2" inside diameter fuel line, or hydraulic lines?hoses, for example should have components for the connections and fittings that have significantly smaller internal cross sectional areas, it does you very little good to use lets say, AN#8 or half inch fuel lines if the internal cross sectional area of the connections and fitting used with those lines is only 3/8" or smaller in cross sectional area,this is an area where dealing with a local hydraulic supply shop that has the correct tools and fittings to custom fabricate your fuel lines, coolant or lubrication lines is a very good idea!
talk to a local professional at your local hydraulic supply, measure accurately, take the time to explain what your trying to accomplish and take several pictures to show them what your doing, and get them too fabricate any high pressure fuel or coolant lines and related fittings




Up to 45 GPH= 3/4 GPM = 5/16" or -04 AN
Up to 90 GPH = 1.5 GPM= 3/8" or -06 AN
Up to 250 GPH =4.2 GPM= 1/2" or -08 AN
nearly ideal for transmission and oil coolers :D
Up to 450 GPH =7.5 GPM= 5/8" or -10 AN
Up to 900 GPH = 15GPM 3/4"or -12 AN





Bosch Fuel Pumps

• Bosch Fuel Pumps have their flow rates defined in N-Heptane as part of their engineering specification. N-Heptane is a pure
chemical and does not have the same viscosity and density as standard petrol. Hence the N-Heptane flow rate figures stated
should be used as a general guide for comparison purposes only.
• Bosch Fuel Pumps are designed for use with standard grade petrol. Subject to statutory warranties, Bosch does not warrant
the performance characteristics or specifications of these fuel pumps if they are used with Alcohol or Ethanol based fuels or
fuel additives that are corrosive.

Part Number........ litres / hour ......(pressure)
0 580 254 023........... 168............ (5 Bar) (72psi)
0 580 254 040........... 102............ (6.5 Bar) (94psi)
0 580 254 044........... 200 ............(5 Bar) (72psi)
0 580 254 046........... 207............ (3 Bar) (43psi)
0 580 254 053........... 175............ (5 Bar) (72psi)
0 580 254 909........... 148............ (5 Bar) (72psi)
0 580 254 910........... 130............ (5 Bar) (72psi)
0 580 254 911........... 95.............. (4 Bar) (58psi)
0 580 254 975........... 165............ (5 Bar) (72psi)
0 580 254 979........... 165............ (5 Bar) (72psi)
0 580 254 984........... 165............ (5 Bar) (72psi)
0 580 464 069........... 98.............. (4 Bar) (58psi)
0 580 464 070........... 130............ (3 Bar) (43psi)
B 261 205 413.......... 200............ (8 Bar) (116psi) ... wrates.htm

GM replacement sending unit. ACDelco part FLS1099


Voltage vs. Flow

In 1996 we did some research into Denso's (formerly Nippon-Denso) in-tank fuel pump flow rates. The biggest surprise was how much voltage affects flow. Also how much flow drops off at higher pressures.

If you measure the available voltage at the battery with the engine running you should see 13.5-14 volts or so. If you then measure the voltage at the fuel pump it's self with the engine running, it will be around 11.9 v and with the fuel pressure regulator loaded with boost pressure the voltage drops to 11.8 v. This is from the small gauge factory wiring being unable to handle the current. The fix for this is to run a large (10 ga. or more) wire directly from the battery to the fuel pump.

To do this you'll need a 30 amp relay (Bosch part #0 332 204 150 or Hella part # 960 388 07 or Porter & Brumfield # VF4-45F11) and the relay wiring harness for it. Any 30 amp 12v relay will work. Try an alarm shop or stereo shop if you have difficulty finding the correct relay. We use a heavy-duty fuse holder with a 30 amp fuse right off of the positive terminal of the battery. Attach the fuse holder to the positive terminal of the battery. The other end of the fuse holder goes directly to terminal #30 (power in) on the Bosch style relay. From terminal #87 (power out) on the relay run the big 10 ga. wire back through the fire wall, under the carpet towards the back of the car. The color for the positive wire to the fuel pump will vary some from year to year. The wire color also changes from one side of the connector to the other. On the car side of the connector the wire will almost always be black with a white stripe. Occasionally it is blue with a white stripe. The large all black wire is always ground. The positive wire will be the other thick wire. Smaller yellow wires are for the fuel level gauge and the low level warning light. Once you go on the fuel pump side of the connector, the positive wire is usually blue.
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Re: reading a dyno BSFC and f/a ratio

LETS LOOK AT A DYNO SHEET FOR A BIT OF INFO ... g_bsfc.htm ... yno_sheet/

NOTICE THE BSFC and fuel/air ratio on this dyno sheet from a LS race engine that makes almost 900hp

lets randomly select 7400 rpm
hes got 608 ft lbs of torque
/thats making about 857 horse power,
near the ideal 12.6:1 fuel air ratio,
.405 lbs of fuel per horse power per hour
a bit of math shows .405 lbs of fuel per hour x 857 hp=347 lbs of fuel per hour or 5.78 lbs per minute.
gas weights close to 6.1 lbs per gallon , so to make that 857 hp hes burning nearly a gallon per minute in fuel.
obviously he will need a fuel supply system that maintains that flow rate, plus a bit more at the injector fuel rail at 40-60 psi or higher
if we assume hes running at 75% of injector flow, so he has some safety margin built into the fuel delivery system, we see that 347 lbs of fuel per hour, delivered =347/75 x100=463 lbs of fuel flow potential, divided by 8 injectors= a 58 lb minimum injector size, (60lb-64 lbs in an injector size selected,makes more sense)
some of you will be wondering why, if the engine runs on 463 lbs of fuel you need a higher fuel pump capacity, the answer is that theres pumping efficiency losses that can easily cut the delivered fuel to less than 60% of the rated flow at 40-60 psi needed at the fuel rails to feed the injectors, Id suggest use of nothing smaller than an#8 lines and AN#10 would be better,and a 140 gph rated fuel pump,absolute minimum, and ID feel much safer with a 160 gph rated at 60 psi pump, MINIMUM, especially once you add fuel filters etc..

notice only the 260 ltr per hour rated pumps, linked to earlier in the thread could reasonably keep up, with demand, and realistically they are too small and not ideal, and have far to small of fuel line fittings



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A few of Top Runners in NHRA NMCA Classes running Turbos & Big HP are using Belt Drive Fuel Pumps Grumpy.
Just like a Crower or Hilborn IR Alcohol Racer.
I think its the best & most reliable fuel delivery system ever.
I have s Bo Laws Belt drive fuel pump for myself.
410 sbc.
Its a hard sell to any Racer. Electric fuel pumps the standard today.
But Belt drive fuel pumps can deliver over 4,000gallons per hour.
A Waterman pump. Top Fuel racing.
Mine is the .500 " wide pump.
Id agree a belt driven fuel pumps, or direct drive off the cam drive, like I used on my Crower / kinsler stack injection
for my big block 1968 race corvette is and was far superior to the skimpy electric pumps, but at over $1000 for the pump and fittings it is not cheap
Best way to install an electric fuel pump for EFI is to install it inside the FUEL CELL OR gas tank. There are MANY reasons to do this:
2. An electric pump pushes fuel much more EFFICIENTLY than it sucks fuel
3. INSTALLING BOTH A RETURN STYLE FUEL PRESSURE REGULATOR AND AN INTAKE FUEL PUMP,allows you to run a return LINE THAT EMPTY'S FUEL BACK INTO THE TANK which keeps the fuel lines cooler and greatly reduces any tendency too vapor lock in a carburetor equipped engine by constantly circulating fresh fuel through the lines and back to the tank.
4. It allows a much more efficient turbine impeller style of fuel pump, which increases pressure and volume of the pump.


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johndeeregarner said:
AutoZone sells a wiring kit for it. Its just three wires and the connector. Would this work? Any idea what that box actually does?
So i have to replace the wiring harness inside the gas tank. But the harness the fuel pump comes with is #1 not long enough and #2 doesn't have that little yellow box on it. My question is, do i need that yellow box? Can i just wire it straight? This box is molded around the three wires.



its simply a variable resister the float arm movement changes the ohms resistance allowing the arms position, controlled by the fuel level, to control the fuel gauge reading

other links that may prove helpful
remember the vast majority if info in any thread is usually in the sub linked info
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Interesting scenario. So I replaced my electric fuel pump in my 87 vette a while back because the original one was making all kinds of noise in the tank. I didn’t have any drivability issues but it just didn’t sound right. I ordered a replacement from Racetronix. While installing the new pump, I discovered the return hose at the sending unit had a kink in the rubber hose section.

(This picture isn't my car, just shows the return hose and where the kink was)

Looked like it had been there for a while. Shortened the rubber hose length to remove the kink and checked to see if that resolved the fuel pump noise with the stock pump, It did. I decided to go-ahead and replace the old pump with the new one since it already had it. Installed the pump with no issues and all is quiet now.

Fast forward a few months. I started noticing a ‘tick’ sound coming from my fuel pressure regulator. I’m 90% certain that the tick is coming from the regulator because I put a stethoscope on it and it’s the loudest compared to the injectors or fuel rail. Again, no drivability problems, fuel pressure issues or leak down problems. All is within spec. Just an annoying tick mostly noticeable at idle.

I stumbled across the box that the new fuel pump came in while cleaning things out the other day and noticed a potential screw up. I noticed the part number on the box was a Walbro 255lph pump. I didn’t intend to order the performance pump but I went back and looked and sure enough, I mistakenly ordered it. A stock replacement pump was what I was after just screwed up when I ordered it.

So, this got me wondering a couple of things,
- Is the 255lph pump too much flow for my stock setup causing the regulator to be overworked and make racket?
- I removed the in tank Pulsator/Dampener with the Walbro pump install. Could this be contributing to the regulator noise?
- I’m not sure if the tick existed before I swapped the pump.

Is this something I need to worry about? What do you guys think?


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in my opinion the regulator TICK sound frequently has nothing to do with the regulator failure issue,being caused by the fuel pump,flow rate, or the fuel pump being used, and it could just as easily have occurred with the stock replacement pump installed as with the higher flow performance pump. yes the regulator may or may not fail, but in most cases its a diaphragm that leaks and that's almost always the result of alcohol or water in the fuel, or not using, or regularly changing a fuel filter, and some fuel injector cleaner additives are not particularly good for regulator diaphragm durability as they contain strong solvents

L-98 Engine Start Sequence

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.

Engine "Catches":

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.


If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

GET out the multi meter, and a fuel pressure gage,
and do a few quick tests for loose electrical connections, look for vacuum leaks and consistent fuel pressure on the fuel rails
and verify the alternator voltage is at or above 13.5 volts,

when things don,t run correctly and the guys that don,t
pull the trouble codes, they are skipping a step that may waste hours

if you don't have fuel pressure in the fuel rail check the fuel pressure regulator

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I am still proud of the One Off C4 ZR-1 Stealth Areomotive 340 Liter X 2 Fuel Pump assemby with true 5/8" all stainless steel lines & #10 AN Fitting connections.
Last I talked to Steve , he has been putting his 1986 Corvette Race car back together.

Words still can't tell all how hard it was to build it.
There is a Return fuel line fuel filter installed on just 1987 Corvettes Bytor.
Mounted direct above primary feed line fuel filter.
Return line filter is plugged up Bytor.
87vette81big said:
There is a Return fuel line fuel filter installed on just 1987 Corvettes Bytor.
Mounted direct above primary feed line fuel filter.
Return line filter is plugged up Bytor.

I wondered what that was. I did't see it described in the service manual. I'll do a quick test this weekend and bypass it to see if that changes things.. Thanks for the tip!


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The return line filter is meant to Dampen Silent the Fuel pressure regulator in operation.
The 1985-86 C4 had complaints of return line drumming & banging noises.
It was an Old TSB.
1988-96 Did without it.
Yep, I think I remember reading about that somewhere. I don't remember it looking like the one pictured above. The last time I was under the car replacing the primary fuel filter, I thought I remember seeing it but it was axial, not like the one in the pic above. I will check it out regardless.

The replacement filter is an expensive sucker.
Re: replacing a c-4 fuel pumpIts

It is a Farm Grain Truck Fuel filter actually Bytor.
Nothing exotic.
I have a spare AC Delco filter element put away.
Bottom spins off. Disposable filter inside.
Should be able to cross over to a WIX #.
Find it for you tonight & post my spare filter element.
Have U-tube vids I want to post too.
Make Phil & Grumpy smile.
Full Pontiac V8 Race Engines Dynoed.
BBC Race power # Territory.