1990 Corvette no spark

Paul E

Member
Hello I have been banging my head on a brick wall for about a month trying to get a new engine to start. 383 Stroker, 1990 Camaro style small distributor, external coil, new ECM, new burned PROM. I have no spark at the distributor. I have an adapter harness from stock wiring to Camaro style small distributer (verified wiring with online schematics), 12 volts to coil. Pulled the new Accell Coil and put on nephews GMC pickup it started right up, pulled distributor (module, pickup coil and rotor intact) put on his pickup, started right up. I have 12 volts from coil to + pin on ignition module, ground on A pin on ignition module. I put noid on an injector and I have pulse at the injectors. I am almost positive I have accounted for all grounds and the external coil is properly grounded to block via bracket. I have put old ECM back on and Old PROM (including variations with new ecm) back in with no change. All fuses appear test good. Engine Spins, 40 pounds Fuel Pressure at rail. Does anybody have any ideas?
 
Ok lets start with the basics ,
(yes I understand its spark and not fuel related)
the first thing ID check is that the oil pressure switch near the distributor base is functional,and the fuel rail pressure is constant at about 38-40 psi, the oil pressure switch,
has a well documented history of not functioning and unless they do youll never get fuel pressure
NEXT Id get out a timing light and hook it up, because youll need to time the engine once it starts.
Distributors:

Depending on the year of your TPI engine will depend on the type of distributor that was used. In 1985-86 "F" body (Camaro-Firebird) and 1985-1991 "Y" Body (Corvette), the distributor was the familiar looking large cap HEI distributor. Upon closer examination of the original distributor you will see it's cap is held down by 4 screws. The more common HEI distributors, if you have another 1974-86 small block Chevy to compare, is held with 4 latches. Another difference is the 4 wire EST connector to the wiring harness. While the common HEI has the prongs with two outer slots facing up, the HEI used on the TPI engines, has one of these slots facing to the outside.
the fact is that due to manufacturing tolerances a dot-to-dot install will frequently be a few degrees off! now most guys might never notice, but it can and frequently does effect the engines power band so getting it correct helps and eliminates one potential source of problems (be damn sure you verify the cams degreed in correctly and the ignition firing orders correct and all the distributor wires go to the correct cylinder,s spark plugs and distributor cap locations)
You can use the common HEI on your TPI for the years mentioned above, but you will have to swap the connector at the harness or find the connectors at a salvage yard, which can be found on the 1985-86 3.8L V6 found on the FWD vehicles or on the 4.1L V8 Cadillac motors.


lg_HEI_2.jpg


Shown above is the large cap HEI distributor, this one is the common variety which the cap is latched instead of being held by four screws. These can have the est connector modified to work on your TPI engine perfectly.

The next distributor was on the 1987 through 1992 Camaro-Firebird TPI engines. This is what I call the "small cap" HEI, which uses a remote mounted coil, typically is bolted to the intake manifold. You will note this is the time period, Chevrolet switched to the roller cam motor, and this distributor was used on these engines.

sm._HEI.jpg


Shown above is the "small cap" HEI with coil.

coil_and_wiring.jpg


The remote coil has two connectors. The gray connector is the 12V coil power supply, the large pink wire goes to ignition "on" power for the distributor, the white wire can be hooked to a tachometer. The black connector has the smaller pink and white wires which goes to the two wire connector on the ignition module on the distributor.

distributor_conn..jpg


EST connectors that send the ignition signal back to the ecm, The one of the left is for the "small cap" HEI, the center one is for the "common" large cap HEI, note the two outer prongs with slots facing up. The connector on the right is the "TPI" distributor connector (1985-86 only), used with with screw down caps. Note one prong with slot facing up, the prong on the far left has a slot but is facing towards the left.

tbi-tpi_distributor_compare.jpg


Be careful in pulling a small cap HEI to use. The distributor to the left is used on the 1987-1992 Camaro/Firebird. Note the smaller base as compared to the distributor on the right, these larger base distributors were used on some 1991-1993 "B" body TBI equipped engines, such as the Chevy Caprice and Buick Roadmaster. They use the TBI throttle bodies which are held down with two studs for the air cleaner, and the manifolds are machined for the large base distributor they use. They will not interchange.

DISTRIBUTOR GEAR APPLICATIONS

There has been a lot of controversy concerning the interchange of the distributors using a large cap HEI on a 1987 and later block and using a small cap distributor on earlier blocks. It used to be on the safe side, use the large coil in cap HEI on the pre-87 blocks and the smaller remote coil HEI on the 1987 and later engines. Now with the aftermarket coming to the rescue for those who want to use the different distributors due to firewall clearance issues, availability, etc. it is possible to use the distributor of your choice, but you must use the proper distributor gear based on the material the cam distributor gear is made of.

Crane cams makes the proper distributor gears for the roller and non-roller blocks.

General rule is to use a bronze alloy gear for a steel distributor gear on the camshaft (most factory roller cams follow this route). For an cast iron cam use a irondistributor gear (all non roller cams and some later aftermarket roller cams use an iron distributor gear on camshaft.

Crane cams does make a coated steel distributor they say is superior to the bronze alloy gear with a OEM life span. It can be found at this URL through Jeg's performance parts: http://www.jegs.com

Part # 270-11951-1

Coated Steel Distributor Gear
Chevrolet
90° V-6 1978-86, 200 thru 262
V-8 1955-87, 262-thru 400 .491'' Dia. shaft
V-8 1965-90, 396 thru 502
  • .491'' Dia.
Crane also makes a iron gear that fits the small HEI distributor for use in an earlier non-roller cam application.

Part# 270-11970-1

Iron Distributor Gear
Chevrolet
90° V-6 1985-91, 262 For GM HEI
V-8 1985-99, 305-350 For GM HEI .427'' Dia. shaft
V-8 1991-00, 454-502 For GM HEI
If you want to use the bronze alloy gear it is part # 270-11988-1 for the small HEI (.427" dia. shaft)

For the large HEI it is part # 270-11990-1 (.491" dia. shaft)
you should have a small cap to factory small base distributor plug adapter?
and verify the pin locations and electrical conductivity

http://ampperformance.com/i-1198424...r-950-distributor-wiring-harness-adapter.html

http://www.hawksmotorsports.com/distributor-connector-87-92-tpi-tbi-small-cap-hei/
smallcapadh.jpg


capsdv.jpg

I see you said your located in
enid OK, we have several members within an hour or two travel that might want to help.

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-84695

http://garage.grumpysperformance.co...stributor-for-your-application.855/#post-9277


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

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-54562

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/
 
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Ok lets start with the basics ,
(yes I understand its spark and not fuel related)
the first thing ID check is that the oil pressure switch near the distributor base is functional,and the fuel rail pressure is constant at about 38-40 psi, the oil pressure switch,
has a well documented history of not functioning and unless they do youll never get fuel pressure
NEXT Id get out a timing light and hook it up, because youll need to time the engine once it starts.

you should have a small cap to factory small base distributor plug adapter?
and verify the pin locations and electrical conductivity

http://ampperformance.com/i-1198424...r-950-distributor-wiring-harness-adapter.html

http://www.hawksmotorsports.com/distributor-connector-87-92-tpi-tbi-small-cap-hei/
smallcapadh.jpg


I see you said your located in
enid OK, we have several members within an hour or two travel that might want to help.

http://garage.grumpysperformance.co...stributor-for-your-application.855/#post-9277

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/
Thank You for replying, as I understand the Oil pressure switch activates the injectors pulsing so if the injectors are pulsing the oil pressure switch is reading greater that 4 pounds pressure. I have a timing light attached and ready for initial timing. The adapter shown is the adapter I am using. Most all threads I have reviewed and I have reviewed a bunch, are about non pulsing injectors, but I have verified that the injectors are pulsing. The distributor I am using is Durafire Distrutor 1987-92 GMC F-Bodie SBC SKU #710-72251 it is new, the ignition module was the first thing I replaced so it has had two new 8 pin modules on it, the second is the one I had working on the 92 GMC
 
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have you tried swapping your suspect distributor in your corvette into a different car,
or swapping a new and totally different distributor into the corvette,
as it seems like from what you stated that your getting the electrical feed (12 volts to the distributor, )
but no spark out of the distributor, which would make me suspect the distributor may be defective,
or that HEI small base distributor, adapter cable may be defective.
or there's an internal electrical short or ground.
I wish I was local to you and Rick, as theres a whole lot of things that you can do during a hands-on inspection and through simple testing that will be very difficult to adequately explain easily.
an ohm meter/multi meter can be helpful,
but it always comes down to isolate and test,
verify the basics, don,t assume, PROVE!


http://garage.grumpysperformance.co...ouble-shooting-rebuilding-hei-ignitions.2798/

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

read these links and
related sub links
pull trouble codes


http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-84695

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=8895&hilit=start+sequence#p8895

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

http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/

http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/#post-71867

http://garage.grumpysperformance.com/index.php?threads/1990-corvette-no-spark.13857/#post-70888

http://garage.grumpysperformance.com/index.php?threads/diagnoseing-tpi-lt1-problems.1241/

reading links and sub links can help
replacement connectors and pigtails are available


http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877

http://garage.grumpysperformance.co...-auto-elecrtrical-connectors.3105/#post-68805

http://garage.grumpysperformance.co...cting-a-distributor-for-your-application.855/

http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46397

viewtopic.php?f=36&t=3105&p=8272&hilit=connectors+pigtails#p8272

viewtopic.php?f=32&t=168&p=41767&hilit=connectors+pigtails#p41767

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-17654


CARCRAFT said:
Easy tests for HEI system:

1. Test for power at the pink BAT terminal. You should have battery voltage w/ the key in the start and RUN positions.

2. Connect the ground side of your test lamp to the battery POSITIVE cable. Probe the TACH terminal on the dist. cap while a helper attempts to start the engine. The test lamp should blink repeatedly as the engine cranks. No blink= bad module or pickup coil. Further testing is required to pinpoint the problem. Blink but no spark = bad ignition coil.

3. Remove the cap & rotor. Remove the green & white leads from the module. Connect your ohmmeter to the green & white leads. You should have approx. 800-1500 ohms depending on the ambient temperature. Open circuit (infinite ohms) = bad pickup coil.

Wiggle the green & white leads as you test. Ohm reading should remain constant if the leads are good. If the reading varies as the leads are wiggled, the pickup coil is bad. You'll often find broken pickup coil leads this way.

4. DVOM (meter) still connected to green & white leads. Set your DVOM to AC VOLTS. Have a helper crank the engine as you watch the AC VOLTS reading. A good pickup coil will produce about 3V AC when cranking. Less than approx. 2V AC indicates a bad pickup coil.

let me take you a little farther...

when you turn the key on.. positive power is sent through the red wire plugged into the BAT side of the HEI cap.. inside the cap you will notice the coil wires have a T shaped terminal.... the red wire goes into the coil.. but it also connects to the right side of the 3 wire harness from the cap to the housing from there to the B+ terminal on the module...


the TACH terminal in the cap.. also has a T terminal.. it also connects to the LEFT side of the 3 wire harness down to the housing and connects to the C connector on the module...

igpi1.jpg


wait.. there is a third wire in the three wire harness... this is where a LOT of problems crop up...
this is the ground strap... it goes into the cap before the coil does.. fits into the middle connection of the 3 wire harness..

the screw that goes through the coil laminations directly over the hooked end needs to have the black wire from the coil..
igpi2.jpg


hei-coil-diagram.jpg

why.... this is the ground for the coil... without it .. the voltage can build up in the frame of the coil till it flashes over like a lightening bolt.. and can be as loud as a shot gun blast going off under your hood..

the center wire goes down and is connected to the condenser hold down strap and the strain relief hold down..

this is really important.. the spark has to make it back up this wire and to the coil after it passes through the spark plugs..



back to the description...

there are 2 screw that hold this coil cover down.. you will notice the TACH and the BAT markings on it..

test with your test light clip hooked to ground to the BAT side.(red coil wire)... you should get voltage...

test with your test light clip hooked to POSITIVE.. the TACH side.(white or yellow coil wire) .. while somebody cranks the engine...

the test light should flash.. this is because the module is making and breaking ground to the C connection inside the distributer. ....... this should make your test light flash..



i normally just remove the module and take it to the parts store as some of them have module testers... where they plug them in and an automated test is run...


i should probably continue on my HEI description...



the 4 pin GM HEI module..

igpi3.jpg

you can see the pins on the right side of this module..

B is the switched ignition power..

c goes up to the Tach and to the yellow or white wire on the coil.

wait.. where is the ground connection.. see the 2 hold down screws... the rivets going through the plastic when the screws go through them ground the module...

why is the ground important.. .. the module connects the C terminal to ground and then breaks that connection to discharge the ignition coil...


on the left end of this 4 pin module are the terminals that go to the pick up coil...

the pick up coil creates a small AC voltage.. usually just about 1 volt AC.. when the AC voltage comes to 0.3 volts positive. the power transistor in the module turns on and grounds the coil.. allowing the electrons to flow into the coil primary creating a magnetic field..

this AC voltage is created by the reluctor spinning above the pick up coil...

this is the second time i have typed this out tonight.. hmm...

when the tips of the reluctor line up with the pick up coil tips.. the voltage will drop back to zero. at this point the power transistor opens .. breaking the connection to ground.. this causes the magnetic field in the coil primary to collapse through the secondary windings and create a high voltage spark....

as the reluctor tips move away from the pick up coil tips.. the voltage continues its negative swing. then it starts rising again as it approaches the tips again..


one of the most important things you can remember.. there has to be dielectric tune up grease under the module or it will die... if it starts again once it cools off does not matter .. once thermally damaged.. its toast.. it will fail eventually.. leaving you stranded... usually at the worst point..
igpi4.jpg
 
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have you tried swapping your suspect distributor in your corvette into a different car,
or swapping a new and totally different distributor into the corvette,
as it seems like from what you stated that your getting the electrical feed (12 volts to the distributor, )
but no spark out of the distributor, which would make me suspect the distributor may be defective,
or there's an internal electrical short or ground.
Hello Grumpy As I stated in the initial post I put my new coil in my nephews 1992 GMC Pickup and it started, I removed my coil and hooked his back up and removed his distributor and replaced it with my distributor that contained the ignition module, pickup coil and rotor and it fired right up, I let it run for about 10 minutes.
 
then the rather obvious conclusion would would seem too be ,you have a mechanical or electrical issue , knowing
that the connections in the wiring harness between the two cars is different,
no spark out of the distributor, which would make me suspect the distributor may be defective,
or that HEI small base distributor, adapter cable may be defective.
or there's an internal electrical short or ground.
and theres some ground or voltage thats present in your 1992 pick-up,
thats not connected in the corvette.
if the coil and distributor both work in your friends engine but won,t work in your corvette, the difference is either the electrical connections or the distributor is not correctly installed , ID start with the basics
pull the cap on the distributor in your corvette and have a buddy try to start the car,
with the distributor cap removed so you can verify the rotor on the distributor is spinning, if its not the cam gear, the cam itself, or the timing chain may be excessively worn or broken
Im sure we can isolate and test and find the source of the problem, but it would be a whole lot easier if I was there!

http://garage.grumpysperformance.co...ouble-shooting-rebuilding-hei-ignitions.2798/


http://garage.grumpysperformance.com/index.php?threads/lots-of-wiring-info-diagrams.317/#post-83877
 
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then the rather obvious conclusion would would seem too be ,
that the connections in the wiring harness between the two cars is different,no spark out of the distributor, which would make me suspect the distributor may be defective,
or that HEI small base distributor, adapter cable may be defective.
or there's an internal electrical short or ground.
and theres some ground or voltage thats present in your 1992 pick-up,
thats not connected in the corvette.
if the coil and distributor both work in your friends engine but won,t work in your corvette, the difference is either the electrical connections or the distributor is not correctly installed , ID start with the basics
pull the cap on the distributor in your corvette and have a buddy try to start the car,
with the distributor cap removed so you can verify the rotor on the distributor is spinning, if its not the cam gear, the cam itself, or the timing chain may be excessively worn or broken
Hello Grumpy I have verified that the rotor turns, there are no burns in the cap, There is no pulse to the tach wire, there is no pulse to the "C" pin, there is ground to the "A" pin on the Ignition Module, There is 12 volts to the Ignition Coil and Then to the + pin on the ignition module, the distributor hold down is snug so there should be ample ground to the distributor. The four wire adapter was professionally made and I have verified that the order is correct. Am I not correct that the pulse to the injectors is controlled by the distributor pickup coil timing, left bank right bank?
 
Hello Grumpy I have verified that the rotor turns, there are no burns in the cap, There is no pulse to the tach wire, there is no pulse to the "C" pin, there is ground to the "A" pin on the Ignition Module, There is 12 volts to the Ignition Coil and Then to the + pin on the ignition module, the distributor hold down is snug so there should be ample ground to the distributor. The four wire adapter was professionally made and I have verified that the order is correct. Am I not correct that the pulse to the injectors is controlled by the distributor pickup coil timing, left bank right bank?
I PULLED OHMS THROUGH EACH OF WIRES ON THE PROFESSIONALLY BUILT ADAPTER AND THERE IS NO RESISTANCE
 
First welcome to the forum! I'm in Yukon Oklahoma, which is just west of OKC.

How did you test for "no spark at the distributor" ?
What kind of cam? Are the valves adjusted correctly? If they never close, then there is no compression.
Compression Check?
Is fuel getting to the cylinders, are the plugs wet with fuel?
 
Pictures, please.
You are using the dual connector remote coil, correct?
So to refresh, you swapped your entire distributor into your nephews GMC truck - WORKS.
You also did the same for the coil - WORKS.
A common problem is the pink & white jumper wire on the 2nd coil connection (the one about 8" long).
That 2 wire jumper is a common failure point.

Again, pictures would help.
 
ok guys sorry it is taking so long to get back to you had to do the family thing I think grumpy is confusing everybody by trying to diagnose a large cap hei distributor when I have a small cap external coil f-body setup on my vette. compression is fine, cam is fine, fuel and delivery system is fine, coil is fine, distributor is fine. I am having issues with signal or voltages coming into my 8 pin ignition module. I need diagnostics on how a computer controlled f-body distributor causes an external coil to fire. I tested the no spark situation by attaching a spark plug to the alternator bracket with a pair of vice grips and watching for spark during cranking. also I followed the procedure grumpy suggested with a test light connected from positive side of battery and tach lead on coil (no pulse). are there any sensors that would stop spark? if it was security system it would not crank. I am having issues uploading photos since I do not have an online storage with a url but it looks just like a 1990 Camaro with a First Performance TPI setup on it
 
I switched my profile picture to an engine compartment picture.
I still need the answers to:
(01) Is it the distributor that signals the injectors to fire - Left Bank Right Bank - if so then the signal is being sent back to the ECM
(02) What signals from the ECM control the initial firing (or not firing) of the Spark Plugs
(03) What sensors might cause the ECM to halt the distributor from firing
(04) I would like to see a chart of the wiring voltages and signal diagnostics for the 4 wire Main Harness to the distributor plug.

In my mind the distributor should stand on its own for the actual start process and the ecm control advance and curve up to 400rpm when the PROM kicks in so there has to be some signal incorrect going to the ignition module stopping it from changing the DC signal to an AC signal and pulsing the ignition coil via the pickup coil.

If the questions were easy I wouldn't be asking the experts (you guys) I know the answer is out there but I have just been spinning my wheels trying to locate it and am hoping one of you can help me. I appreciate all constructive help.
 
I am having issues uploading photos since I do not have an online storage with a url but it looks just like a 1990 Camaro with a First Performance TPI setup on it

You don't need a photo hosting site like PhotoBucket, it's best to upload them to the website. That way they are always available.

Follow the link below and page down until you find the section Posting Photos.

http://garage.grumpysperformance.com/index.php?threads/taking-and-posting-clear-photos.5595/
.
 
Thanks INDYCARS you tha man, I was attempting to use the photo upload icon

index.php
 

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left click opens file
right click displays image address
placing the address between the brackeded info
(use IMG not VMG in the brackets
[vmg](address here) [/vmg]

displays picture as you can post it
 
3 Inch Tucked Exhaust
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