GM Ignition problem

[David Reyes]

I posted this on the last live show but even when I try to make it short Eric couldn’t take it because it was too long. I apologize about that.

This is the full story:

I have a 1989 Pontiac Firebird Trans Am GTA 5.7L
After a month sitting on the garage I tried to start it up and it will crank but not start.

I check the fuel pressure with a gage and I have Fuel. Recently I had to replace the fuel Pump the gage wont maintain pressure (I believe a bad regulator) but since it did not start discarded this as the problem.

I check for Spark on Number one Spark Cable and had no spark.
I proceeded to check Spark coming from the Coil and had no Spark
I then check for the signal coming from the Ignition Module to the Coil and no signal detected. But I did had the 12 volt on the red wire

I got the distributor Cover off and found that the pin that connects to the center port where the coil fires into was broken and no spring motion to the part that was left. (AJA Moment)

I check for the voltage on the pickup coil and the result where steady not fluctuating but I had a Volt Metter not an oscilloscope so I didn’t trust that result.
Then I try to duplicate the signal from the pickup coil to the ignition module to see if it send a signal and no signal where trigger by the Module
Then I try to duplicate the signal to the ignition Coil to see if it fire but didn’t fire

My hypothesis at this point was that when I started the car the piece broke and the hi voltage from the coil become like a (EMP) and damage the surrounding electronics.

I replace the Pickup Coil. Tested it and the voltage fluctuated a lot better than with the old one
I replace the Ignition module and tested it to send a signal to the coil and it did
I replace the ignition coil and tested it to fire and it did once. Subsequent test to fire the ignition coil was unsuccessful.

I decided to put everything back together and give it a try. Since I had taken the distributor out I had to do the basic timing so I disconnected the computer brown cable that control the timing and start the car and it started at his point I believe my problem was over.

I did the initial timing 6 degrees BTDC but the engine was missing a bit and the mark move back and forward.
Then I connected the Brown computer cable I started the engine again and this was very bad so bad that it stall and died.

A Few weeks later I took all the spark cables out and route them very nice and separated. I check for voltage leak with water and dark the garage. I saw no voltage leak and I have recently before this problem had replace Cables and spark plugs for maintenance.

I try again and the same result at this point I’m thinking that it may be the computer but don’t know if it’s wrong input or the computer itself. So I decided to replace the computer and when I put the new computer I first started the car with the brown cable disconnected.
Put the base timing again and this time it was not missing and the mark didn’t move like before.
Then I connected the brown cable back and started the engine and it started at hi Idle for about 30 seconds and then it stall like before. Try a few times and it can’t keep idle with the computer connected.
Since the computer is remanufactured I believe I have some input to the computer bad but need to know what to check next.
Sorry for the long message please help.

Topic

[James]

Your best to get a wiring diagram for the ignition on that vehicle and follow that. Check powers and grounds where applicable. Also does that computer have to be reprogrammed? Best of luck.

[David Reyes]

This is a OBDI so an old computer tat the programming is in a chip that I had to transfer from the old computer.

[Mike]

No intention to insult you and I understand that you are trying to be as informative as possible —but the resulting post is too hard to follow.
If you answer all questions briefly, then more people may be able/willing to help you.

Here is what I would like to know:

1) What exactly is the present problem?
Is it: A)Cranks but does not start
B ) Starts but runs badly
OR
C) Starts but stalls after initial fast idle

You said you replaced the pickup coil, ignition coil, ignition module and spark plug wires
Were any other parts replaced to fix the present problem?

Do you presently have low fuel pressure OR have normal fuel pressure but it drops after the car is shut off OR what is presently going on with fuel pressure?
Is there presently a problem with erratic spark?
Did you replace the distributor cap and rotor or not?
After you FIRST replaced the spark plug wires ,did you then start and drive the car?
When you recently rerouted the spark plug wires, did you double check that ALL wires are connected to the right spark plugs?

Did you follow the instructions that came with the replacement ECM exactly?
If not, your computer may need to do an idle relearn to stop it from stalling at idle.
The instructions that the ECM came with should tell you if it’s necessary.
Yes, I understand that this is an OBD 1 system.

[Author]

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