I have an 85 H model Trans Am. I've been trying to get spark for months now. Here's everything I've replaced and gone over:
Distributor cap
Rotor cap
Plug wires
Primary coil
Pick-up coil
Ignition module
ESC module (my car isn't supposed to have one but it does)
Fuses
Starter wires
Grounds
Fusible links
ECM
PROM chip

I think that's everything, but I've gone over so much concerning this problem that I might be forgetting something. I didn't buy any bad parts either, they've all tested good.

It really shouldn't be this hard to solve a spark problem on this car, it's not that sophisticated of a vehicle. The one thing I'm unsure of is the Check Engine light not coming on with the key in the ON position.

So at this point, if no one can tell me anything to help me out with this I want to remove all electronics and go with a hotwire to an HEI distributor. The car would surely start then. Has anyone done this? I don't have a clue where to start if I do decide to do that.

 

I assume you've tested for power at the large pink or red wire at the cap, while cranking.

 

Not while cranking, but it does get 12V with the key ON. What would cause it not to have power while cranking?

 

Have you checked the ecm fuse by the battery

 

Check the 3wire connection to the cap. I pushed mine in and would crank over but wouldn't start. I turned it around and plug it back in and it fired off.

 

A bad ignition switch can cause no power to the ignition even though the starter cranks.

 

Does your car have the ATS system? My Iroc done this and it was the ATS.

 

crank pos sensor?

 

Wouldn't it still get spark just not at the right time? I have no experience with any form of fuel injection.

 

eh I dont think so, I had trouble in one of my cars where I couldnt get any spark what so ever and it was the crank pos sensor.

 

Have you checked to make sure that the dist. base is making contact with the intake manifold? The distributor base serves as teh ground for the module, and if its dirty, the ignition will not start. The ground path is thru the base, then the hold down clamp, then the intake manifold. If any contact point is dirty, the module will not ground and will not give much of a spark. I had it happen to me. The quick on the spot, get you home fix was to take some bare copper wire, and twist it around the distributor base, and around teh body groundstrap. Run a temporary ground wire to the actual base of the distributor and see if that gives you spark.

 

Maybe the clamp can cause ground, but there is a gasket between the base and the intake manifold so I don't see how that could be a ground path.

 

try it with the tach wire disconnected-if that is grounded
out it might cause a no-spark.

 

I replaced the ignition switch, and checked the big red wire while cranking and it gets about 8 volts. The ECM fuse near the battery is good. I don't know how I would disconnect the tach wire without cutting it. And the 3-wire connector only plugs into the ignition module one way, which is the way I have it.

 

Your car has the large body HEI. The tach connects to the dist via a white wire attached to the "TACH" terminal on the cap. Are you sure you got everything back together right in the cap? There is a ground strap that installs under the coil. Did you get it back in? Also, the button under the coil and the rubber seal.

At this point, you may want to test for primary ignition pulse to the coil. By attaching the ground clamp of a 12v test light to the batt+ terminal, you should get a steady flash on the tach terminal when cranking.

 

The original motor seized up, and it was replaced with an LG4 out of an 87 Camaro. The distributor, module, and coils also came out of that Camaro. I'm not sure if it's an HEI distributor, but the primary coil is mounted on the intake manifold. There's a pigtail with the big red wire and white tach wire that plugs into the primary coil. Is that what you're talking about? I'll try that test when I get some time in the next day or two.

 

The clamp is the ground path. If that gets dirty underneath, the coil will not fire. Its important to keep the clamp, and the areas on the intake and distributor base that it contacts clean to ensure a good ground.

 

If your car has the VAT system it could be a bad key.

 

Okay then, you have "small body" or external coil HEI. Same idea applies. Check for power at the large red wire at the coil while cranking. Verify good connections on the small black coil connector that goes with the gray coil connector. The red wire in that black connector provides power to the dist from the red wire at the coil. Check the harness of this connector for chafing.

You should get a flash on a 12v test light when you push it in beside the white wire at the coil(backprobing), with the ground clamp of the light attached to batt+.

Dimented mentioned condition of the grounding surfaces and dist hold down clamp. Check these as well. Check both dist connectors for damaged or backed out terminals.

 

I did this and the light stayed light with the key off, and unlit when I turned the key on or cranked it. I checked the connectors and they look good. One or two of them are new, I changed them out at some point during this process of trying to find the problem.

 

try changing the crank sensor, if crank sensor is bad it wont get spark at all, same thing with a cam sensor too allthough im not sure if it will get spark if the cam sensor is bad i kno it wont stay running tho. but if the crank sensor is bad you wont get spark

 

I didn't think thirdgens had crank or cam sensors, I know my car doesn't.

 

No cam or cvrank sensor on third gen V8s. The pole peice and timing core produce a crank referrence signal for the ECM to use for injector and timing control.

Im confused. Which wire was hot with the key off? There should be no power to either the red or white wire with key off. The red should be hot in run or start. Verify this. If this is not as stated, check any work you've done on this wiring. The red wire gets power from the ignition switch, through C100 connector. Trace it back to the switch with your test light. It has to have 12v in run or start, and no power otherwise. If this is not as stated, check the ignition switch.

The ign switch is fed by two large red wires from a fuse link at the starter. These both need to be hot at all times. Verify that neither one loses power under load.

 

double check your timing.had the same problem on my 87 and the distributor was out 180 degrees. make sure the motor is set to top dead center and make sure the rotor is pointing towards CYL #1 on the cap. Worth a shot

 

The timing is set to TDC. And asedoc, I connected the test light ground clamp to the battery positve terminal, and with the power off the light stayed lit when I touched it to the white tach wire. As far as the fat red wire, it gets 12v while on and cranking. I'll check on the two wires coming from the starter that you mentioned.

 

I had trouble starting my t/a after having all the accessories off the front. Finally I noticed that the battery ground (-) to alternator bracket wire wasn't tightened down at the bracket. Check there.

 

No need to worry about the wires at the ign switch. We know now that you're getting power to the coil. Your car should have two white wires at the coil. One is with the red or pink wire to the distributor. This wire carries the primary ignition pulse from the ign module to fire the coil. The other white wire at the coil is rpm referrence to the tach. You can determine which is which by tracing each of the two.

The PIP wire is in a short harness from the coil to the dist. The other will go into the main engine harness. There should be an inline connector in this wire where you can disconnect and isolate the circuit. Do this and try the flash test on the white wire again. If still no luck, try cranking the engine with EST timing connector disconnected. The EST system operates independent of the ECM below 400rpm. If there is a defect in the EST module of the ECM, or a short in the harness, it can pull down the signal and kill PIP.

If you still have no spark with the EST disabled and tach circuit isolated. Then there is either a short in your crank referrence circuit(purple/white wire) from distributor to ECM which can pull down the PIP signal, or you have a defect in your distributor. Most common failure is the ign module(they can test good all day long and still not work). The next most common is the pick up coil. There can also be grounding issues. Im assuming youve already checked dist to manifold ground as recommended earlier. You may end up needing to try a different distributor.

 

Darn, I almost forgot. Try the flash test on the white wire with it isolated from the coil. This is tricky as the power supply to the dist is in the same connector as the PIP circuit. However, it can be done using care and an aligator clip providing 12v to the red or pink wire going to the dist. This test is to verify that the coil isnt your problem. I assume that you've checked spark at the coil wire.

 

There's a guy working at O'Reilly who's going to let me try one of his old style HEI distributors, the kind that only has one wire to power it from the fuse box. He said that should work and if it doesn't then I'll just give him the distributor back. If it does work, then I'll be out $120 and be able to drive my car for the first time in 2 years. If for some reason it doesn't work I'll continue to take all the help I can get from you guys.

 

That dist wont work in your car. Not if you have EST. With EST, the ECM controls timing and is connected to the dist through the 4 wire connector from the ign module. Without input from the dist, the ECM will not produce injector pulse or activate the fuel pump relay on engine crank. Your lock up torque converter wont work and drivability will suffer as the ECM wont have an engine RPM referrence. Unless you plan to make significant changes in your engine management, you have to stay with the style dist your car was made with.

 

I figured I'd update this thread to let everyone know that I put in the old style HEI distributor, disconnected the computer controls, and the motor starts now. It's great to hear it run after nearly a year. I never figured out what the problem was as far as not getting any spark, but I don't have to worry about that now with this distributor. Thanks for all the help though.