C4 started running like crap after running out of fuel

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
douglasdavis42 said:
I probably already know what my problem is but wanted to check it out first. About 2 weeks ago I ran my 1996 vette out of gas, I know stupid , dumbass me. Anyway since then the car starts and runs but when you shut it off and let it sit an hour or two is will not restart. It will turn over but wont start. Not flooding because there is no smell of gas, but if you let it sit several hours and go back it will start and run great. So I filled it up with high octane gas and some sea foam and proceeded to run it thru. Ran about half a tank out in a couple of hours, car ran great. This am I go out and going to town (not shutting it off) I run my errands and on the way home it started stuttering, bogging, back firing, spitting, and sputtering. When I shifted to Neutral and pumped the pedal it would stay running barely. When I stopped pumping it died. Seems like it isn't getting any fuel, so my solution is to change the fuel filter, fuel pump, and strainer and see what that does. Anyone have any other ideas???
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READ
THE LINKS AND SUB LINKS,
THEY CONTAIN A HUGE AMOUNT OF RELATED INFO
PULL THE TROUBLE CODES

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://www.summitracing.com/parts/tff-8173nep/applications/year/1996

http://members.shaw.ca/corvette86/FuelS ... gnosis.pdf

http://garage.grumpysperformance.com/index.php?threads/testing-leaky-fuel-injectors.7310/

http://garage.grumpysperformance.co...ystem-trouble-shooting-flow-chart-info.11536/

http://garage.grumpysperformance.com/index.php?threads/replacing-a-c-4-fuel-pump.33/

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477

http://www.harborfreight.com/fuel-injection-pump-tester-92699.html

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below youll find several links, and sub links,
that may take you several hours to read through,
but it will save you a great deal of time and money to do so carefully.
read through all the linked info it contains a good deal of related info youll need to look through and understand to boost the TPI engines power effectively.
Knowing what your dealing with, what the stock parts can do, and what should be modified or replaced, and what you can do to enhance , increase and broaden, the power is 1/2 the battle here.
(take notes and ask questions)
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https://www.harborfreight.com/11-piece-noid-light-and-iac-tester-set-97959.html
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https://www.jegs.com/i/JEGS/555/W89...MIoLGlpLnz3gIVDFYNCh36aAK4EAQYAiABEgKTIvD_BwE

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C4 Corvette Start Sequence for L-98 Engines

When starting an L-98 Corvette engine, a sequence of events take place that precedes the engine running. Knowing these sequences will help you troubleshoot no start issues with your C4 Corvette.



      • Fuel Rail Pressurization
      • C4 Corvette Start Sequence begins 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 Schrader valve on the passenger side fuel rail near the rear of the engine and proper fuel pressure after the pump runs should be between 40-42 pounds of pressure. The reading will drop to 38-40 pounds after the engine is running.
      • Initial C4 Corvette Start Action: Once rotating the key to the start position if the anti-theft system has not disabled the starter the engine will rotate.
      • Once the oil pressure has reaches 4 PSI, the oil pressure switch contacts will close allowing the fuel pump to run. Note that you should have a black color oil pressure switch/sender. This sender is mounted behind the distributor on the driver’s side. If its not replace it with one that's only black. If the car fires then stalls replace this switch.
      • The distributor outputs rotational frequencies to the ECM (Engine Control Module) as a result of the engine being rotated by the starter. This frequency continues as long as the engine turns (both starting and running) if no frequency output is present the engine will not run.
      • ECM Outputs : Once the ECM sees oil pressure greater than 4 PSI and the reference frequency from the distributor the ECM will command the injector drivers which will begin pulsing the injectors open for 4 ms (milliseconds) periods. (The L98 injectors all fire on one side of the engine at the same time followed by all injectors on the other side firing at the same time. The LT-1 fires the injectors individually per the firing order).
      • Brainiac Fact for C4 Corvette Start Sequence! The ECM also pulls the fuel pump relay which makes the contacts and parallel's it electrically with the oil pressure switch. This way if the fuel pump relay fails you can still normally get the car to run. This will only happen if you make at least 4 PSI oil pressure. This “limp home mode” feature was put in place to allow for a fuel pump relay failure.
      • The ECM requires an input from the TPS (Throttle Position Sensor which is mounted on the throttle body assembly) required voltage is .54 volts DC. Greater than 0.54 volts the ECM will assume the engine is flooded. This logic is triggered by the driver when pressing the accelerator pedal to the floor. The flooded condition would clear as a result of restricted fuel flow. The output of . 54 volts during start and idle from the TPS is very important in both starting and run performance. Its important to have a good voltmeter to troubleshoot something with such low voltage. Poor quality voltmeters can be inaccurate up to .2 volts.
      • Assuming the ignition module has spark of sufficient intensity to ignite the air-fuel mixture the engine will start.
      • C4 Corvette Start Sequence of Engine "Initial Start" for 1985 through 1989 L-98: When the engine initially starts, the MAF sends a signal to the ECM reporting that air is flowing at "XXXX" hertz frequency through it and into the intake manifold. The ECM refers to its Airflow Table for ECT conditions of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms this supplies a proper air/fuel mixture for combustion. For information on the 1990 and 1991 L-98 see below.

    • Note 1990 and 1991 L-98 : 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.
    • GM 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 calculates air flow indirectly. Errors and vacuum leaks 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.
    • Initial engine idle speed of should be around 900-1100 RPM and then slowly decay to around 600-700 RPM unless the air conditioner is on at which case it will run at around 800-1000 RPM depending on pressure altitude. If this does not happen, the Idle Air Mixture Valve or IAC may be plugged or faulty. You could also have an intake manifold leak or another vacuum leak. Check for vacuum leaks.
Engine Running





      • ECM Open Loop Mode: In "Open Loop" mode the ECM is controlling the air/fuel mixture by referencing generic values stored in the ECM Flash memory. These values do not benefit from from the O2 sensor monitoring and lean rich correcting factors.
      • After the C4 Corvette Start Sequence is finished the Oxygen Sensor (mounted in the exhaust pipe) indirectly is considered to have reached operating temperature of several hundred degrees when the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) is 160 degrees. This would be a Boolean logic type of result. In simple terms X+X+X= Output "Y" The computer then switches to "closed loop" mode meaning the Oxygen sensor’s output is being referenced and being used along with the MAT and ECT outputs for the ECM to adjust the injector pulse widths (more “ms longer” or less “ms shorter”) to maintain a 14.7:1 air/fuel mixture.
C4 Corvette Start Problem Summary
If you have a no start condition or if your C4 Corvette starts and then dies, check the above items in sequence to see if all the events are occurring as stated.

Having the proper tools make this job much easier and are highly recommended for troubleshooting these sorts of problems.

are you getting ignition spark at the plugs immediately, as the car initially cranks , or only once the keys released?
whats the oil pressure read as it cranks?
any FUEL LEAKING from the regulator if the vacuum hose is removed? (it could take 2-3 minutes to start dripping)?
are you pulling and trouble codes?
can you post clear pictures of each spark plug (labeled as to cylinder location number (1-8) ?
are both injector fuses testing good?
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replacement injector pig tails are available at rock auto for less than $5 each
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https://www.summitracing.com/parts/anm-cp7838
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and rev the engine a few times and watch the fuel pressure it should in theory remain in the 38 psi-42 psi range for most TPI and TUNED PORT efi


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HOW ABOUT verifying WHAT THE ISSUE IS (OR IS NOT) WITH A FUEL PRESSURE GAUGE!
AND
pull trouble codes
RULE#1
never assume a damn thing ISOLATE ,TEST AND VERIFY
you might be amazed at the number of times I see guys who are spending a great deal of time trying to CURE a problem that does not really exist and ignoring a problem that does based on the erroneous assumption some component has failed.
this is due to the fact they assumed they knew, what was wrong,
but never bothered to test and verify what the true problem was, what they thought it really was , before buying and installing parts.
This can and does result in the purchase and installation of Parts that in many cases they did not need , probably could not easily afford and only later found were not needed after the true issue was found after installing the new parts failed to correct the problem, and they were forced to look further, and were then forced to buy more parts that they only found they needed after testing, when installing the parts they thought they needed failed to resolve the issue!
If you were local Id suggest you bring it by the shop, but thats obviously not an option, so you need to find the cause thru testing and correct it.
you'll need to isolate it to,the individual cause yes you most likely over heated and damaged your fuel pump, fuel pumps are cooled by sloshing fuel and ideally you should never run less than a 1/4 tank so the pump remains well cooled.
Id suggest hooking a fuel pressure gauge to the shrader valve on the fuel rail, you should see. 38psi-45 psi, 42 psi is the intended designed pressure
buy a CHEVY SHOP MANUAL FOR YOUR YEAR CORVETTE!
you always need a base line to start from, on a TPI corvette.
a logical step by step approach and keeping accurate notes helps.
youll NEED a multi meter, a shop manual and a timing light and fuel pressure gauge at a minimum, a few carefully done logical test's to isolate the cause and once found actions too correct it once , you know the cause rather than random guess work will provide the answer and cure rather quickly
set and verify your ignition timing, pull trouble codes,set your tps and iac,, then check for vacuum leaks on the lines and intake,then get out your multi meter and verify all the sensors, chances are good its a defective heat sensor or defective o2 sensor, 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
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http://www.harborfreight.com/5-in-1-dig ... 98674.html
put a fuel pressure gauge on the fuel rail on the shrader valve,

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a vacuum and fuel pressure gauge is useful
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performance issues or troubles like you describe, generally fall into 5 basic groups
you can,t make intelligent choices with out knowing the facts about exactly how things are supposed to work, and testing to verify that they are working currently as they were designed too or not
MECHANICAL--things like worn cam lobes , badly adjusted valves ,vacuum leaks, rusty distributor advance weights and springs,

FUEL DELIVERY-- things like clogged fuel filter or defective fuel pump, bad fuel pressure regulator, wrong power valve or jets, defective fuel pumps and accelerator pumps in carbs

IGNITION-- things like incorrectly set,timing advance curve or bad wiring , old spark plugs , burnt ignition wire, the wrong plug gap, cracked distributor caps etc.

SENSORS,computer controls and electrical connections, too sensors and computer controls

Improperly input or corrupt software when you have the option of changing the data
HOW ABOUT verifying WHAT THE ISSUE IS (OR IS NOT) WITH A FUEL PRESSURE GAUGE!
AND
pull trouble codes
RULE#1
never assume a damn thing ISOLATE ,TEST AND VERIFY
you might be amazed at the number of times I see guys who are spending a great deal of time trying to CURE a problem that does not really exist and ignoring a problem that does based on the erroneous assumption some component has failed.
this is due to the fact they assumed they knew, what was wrong,
but never bothered to test and verify what the true problem was, what they thought it really was , before buying and installing parts.
This can and does result in the purchase and installation of Parts that in many cases they did not need , probably could not easily afford and only later found were not needed after the true issue was found after installing the new parts failed to correct the problem, and they were forced to look further, and were then forced to buy more parts that they only found they needed after testing, when installing the parts they thought they needed failed to resolve the issue!
If you were local Id suggest you bring it by the shop, but thats obviously not an option, so you need to find the cause thru testing and correct it.
you'll need to isolate it to,the individual cause yes you most likely over heated and damaged your fuel pump, fuel pumps are cooled by sloshing fuel and ideally you should never run less than a 1/4 tank so the pump remains well cooled.
Id suggest hooking a fuel pressure gauge to the shrader valve on the fuel rail, you should see. 38psi-45 psi, 42 psi is the intended designed pressure
buy a CHEVY SHOP MANUAL FOR YOUR YEAR CORVETTE!
you always need a base line to start from, on a TPI corvette.
a logical step by step approach and keeping accurate notes helps.
youll NEED a multi meter, a shop manual and a timing light and fuel pressure gauge at a minimum,
set and verify your ignition timing, pull trouble codes,set your tps and iac,, then check for vacuum leaks on the lines and intake,then get out your multi meter and verify all the sensors, chances are good its a defective heat sensor or defective o2 sensor, 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
1996_Corvette.jpg

image_6238.jpg

http://www.harborfreight.com/5-in-1-dig ... 98674.html
put a fuel pressure gauge on the fuel rail on the shrader valve,

2713s.jpg

a vacuum and fuel pressure gauge is useful
tpishrader.jpg


performance issues or troubles like you describe, generally fall into 5 basic groups

MECHANICAL--things like worn cam lobes , badly adjusted valves ,vacuum leaks, rusty distributor advance weights and springs,

FUEL DELIVERY-- things like clogged fuel filter or defective fuel pump, bad fuel pressure regulator, wrong power valve or jets, defective fuel pumps and accelerator pumps in carbs

IGNITION-- things like incorrectly set,timing advance curve or bad wiring , old spark plugs , burnt ignition wire, the wrong plug gap, cracked distributor caps etc.

SENSORS,computer controls and electrical connections, too sensors and computer controls

Improperly input or corrupt software when you have the option of changing the data
obviously the basics always apply ,
you need to think carefully, don,t assume anything.
TEST AND VERIFY EVERY COMPONENT AND SENSOR FUNCTION!

of checking the need to verify your actually getting fuel out of the injectors,
your alternator produces 13.5 plus volts,
your getting spark at the spark plugs ,
your getting compression in all cylinders,
ALL the sensors are fully functional,
your getting at least 10 psi of oil pressure as the engine spins while its trying to start,
you need to see the fuel pressure is consistently at 38-42 psi.
you need to verify the fuel filter and fuel pressure regulator and return line are functioning as designed.
verify all the electrical grounds are good,
and you use a noid tester to verify your getting the injector pulse.
what most people fail to do is test and verify, you can,t assume anything. youll want too verify, youve got no plenum or runner vacuum leaks, and the catalytic converters are NOT restricting exhaust flow.
just because the injectors have pressure in the fuel rail, and get a pulse does NOT insure fuel flow thru them,
and having fuel rail pressure does not insure ITS GOOD fuel,
it can be tainted with water or rust particles in the fuel,

preventing fuel atomizing in the cylinders.
clogged catalytic converters can easily cause the engine to fail to flow air,
checking the plenum vacuum and exhaust back pressure and reading the exhaust fuel/air ratio,
use of an infrared temp gun, to verify cylinder exhaust temps are reasonably equal and a multi meter to set the TPS sensor and verify the ignition wire resistance will help.
simple stuff like verifying the firing order that you just know is correct (which may not be , so VERIFY IT) get over looked
and testing the coil and oxygen sensors and temp sensors sure helps

After you verify theres consistent strong electrical spark at the spark plugs when your trying to stasrt the engine and fuel pressure is consistent at the fuel rails,and your getting at least 7-8 psi of oil pressure,
IF you suspect a fuel delivery related issue, a good long spray of starter fluid into the throttle body and trying to start the engine with that extra fuel source may prove informative, if it trys to start with the extra fuel in the plenum but failed to start without it, its a good indicator the injectors are plugged or defective
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if you suspect water in the fuel pull the inside of the shrader valve
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with a valve tool, and slip 12 feet of braid re-enforced 5/16" pvc hose over the valve ,
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clamp it with a screw clamp
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on the valve so theres less chance of a fuel leak, and let the fuel pump push a 1/2 gallon of fuel out of the fuel rail into a clear glass container on the floor , allow it to settle for 15 minures and look for water to settle out of the fuel.
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http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/


http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.com/index.php?threads/replacing-a-c-4-fuel-pump.33/

http://garage.grumpysperformance.com/index.php?threads/c3-c4-corvette-vacuum-diagrams.1773/

http://garage.grumpysperformance.co...ckpressure-hurting-your-combo.495/#post-26600

http://garage.grumpysperformance.com/index.php?threads/what-kills-o2-sensors.3049/#post-51701

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477
the basic tools youll need, are common mechanic hand tools plus....


the correct matching SHOP MANUAL
TIMING LIGHT
IR TEMP GUN
VACUUM GAUGE
MULTI METER
FUEL PRESSURE GAUGE
COMPRESSION TEST GAUGE


irtemp.jpg

http://www.professionalequipment.com/ex ... ermometer/
Wide temperature range from -58 to 1832°F (-50 to 1000°C)
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viewtopic.php?f=55&t=109
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when your chasing potential problems ,with your c4 corvette, don,t get over whelmed!
never assume a damn thing, ISOLATE ,TEST AND VERIFY, DON,T GUESS!
its got several basic systems like fuel delivery, ignition, mechanical, sensors and likely problems like loose electrical connectors, burnt fuses, and the fact the cars 20-30 years old,to isolate the source of any problem,
its simply a case of ISOLATE and TEST!
PULL THE TROUBLE CODES ,
AND VERIFY SENSORS ARE GIVING THE CORRECT READINGS.
If the cars down on power ,but seems to run without an obvious miss, or stumble, in this case the more likely issue is a partly clogged catalytic converter, restricting exhaust flow, a couple partly clogged injectors or a worn cam lobe, a faulty OXYGEN SENSOR, , or maybe the fuel filters, partly clogged or your engines seeing a lack of effective fuel pressure, due to a leaking fuel pressure regulator.
the point is you don,t know what is the cause of any problem , is until you TEST!
but it could be a dozen other things and the correct course of action is simply ISOLATE and TEST!
you NEED a factory service manual and a few tools!
You NEED to have a logical step bye step test and isolate procedure!



http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46303

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/

http://garage.grumpysperformance.com/index.php?threads/maf-burn-off-relay-info.661/

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477

USEFUL LINKS TO RELATED INFO

viewtopic.php?f=70&t=2798

viewtopic.php?f=70&t=4683

viewtopic.php?f=70&t=1015

viewtopic.php?f=50&t=9478&p=34812&hilit=leakdown+test#p34812

viewtopic.php?f=70&t=202

http://garage.grumpysperformance.co...ory-service-manual-question.11202/#post-50528

viewtopic.php?f=50&t=609

viewtopic.php?f=55&t=1639

viewtopic.php?f=50&t=268&p=324&hilit=power+valve#p324

viewtopic.php?f=52&t=196&p=231#p231

THESE LINKS SHOULD HELP
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-51440

http://garage.grumpysperformance.com/index.php?threads/replacing-a-c-4-fuel-pump.33/

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/

http://www.digitalcorvettes.com/forums/newreply.php?do=newreply&p=2993137

http://garage.grumpysperformance.co...g-tpi-crossfire-or-lt1-vette.1401/#post-22501

http://garage.grumpysperformance.com/index.php?threads/replacing-a-c-4-fuel-filter.1470/#post-3304

lots of related info on trouble scanners and software diagnostic tools

viewtopic.php?f=27&t=3096&p=18612&hilit=scanners#p18612

viewtopic.php?f=50&t=6323&p=19860&hilit=computer+cable#p19860

viewtopic.php?f=50&t=8136&hilit=obdII

http://www.haltech.com/product/platinum ... /sport-gm/

viewtopic.php?f=32&t=2697&p=8434&hilit=computer+cable#p8434

viewtopic.php?f=2&t=3074&p=8155&hilit=computer+cable#p8155

viewtopic.php?f=32&t=9202&p=33208&hilit=computer+cable#p33208

viewtopic.php?f=80&t=728&p=9217&hilit=+sensors+location#p9217
 
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douglasdavis42 said:
I got home this afternoon and started testing, I isolated the problem, and then I repaired it. Took a fuel line pressure gauge (borrowed from auto zone) and took a pressure reading, 12 PSI. So I was planning on changing the fuel pump any way so I took the old one out and installed a new fuel pump. Took all of an hour to complete, only because I didn't know what I was doing lol. The next thing was the fuel filter, that took a little more doing to figure out how to get it off and replaced. But after a little time I was able to complete that as well. I then took another pressure reading and I see where I am now at 42 PSI. So I took the vette out for a little spin to "check it out". After spinning the tires and seeing that the performance was greatly increased, I am in love with it all over again. Thanks guys for all the help and advise it was all helpful.:partyon:
 
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