Pontiac Repair: 1991 firebird cranks over fine but wont start, voltage coil, pickup coil

Question
QUESTION: Hi Todd,
I have a 1991 firebird 3.1L V6 auto trans
It ran fine one morning for a short trip and later would not start even with starting fluid sprayed in the throttle body.
I have replaced the pickup coil and ignition module in the distributor along with a new cap and rotor.
The high voltage coil was replaced not long ago also.
It seems to get intermittent spark at the plug.
I plan to replace the ECM computer under the dash next but wanted to see what your thoughts were.
Thanks for your time and efforts here.
Eric

ANSWER: Hi eric:

Well the computer is not going to cause a No or intermittant spark issue. The spark when the engine is cranking is controlled by the ignition module and the distributor. The computer control spark timing once the car starts and it controls the fuel injection. I would check for a few things. Amke sure all the grounds on the engine are clean and tight including the battery connections. Then make sure you have a good 12 power feed to the coil use a halogen headlamp bulb across the 2 wires at the coild for the power and ground they are the pink and black wires turn the key to run it should turn the bulb on bright if not you havew to trace your loss of power and or ground. Then check it when the car is cranking. it may be a bit dimmer due to the load of the starter motor but still it shouldn't go out. If that is good then check the wire harness between the dustributor and the coil for and rubbed through pinched or broken wires. That is where I would start looking. Also make sure the distributor you put in this car is correct for that year make and model car. You could be chasing your tail due to the wrong parts put in the car. Good Luck :)


---------- FOLLOW-UP ----------

QUESTION: Hi Todd,

I inadvertently said that I put a new cap and rotor on, but I was thinking of wrong car. The old cap had the center spring loaded prong worn away, which could explain the problem, but I DID NOW put on a new cap and rotor but now there is absolutely NO SPARK.

Correct distributor for car.
Had the ignition module tested - it tested good.
New pickup coil tests good (800 ohm)
High voltage coil tests good.
Good halogen power on pink wire of coil at run and crank positions :-)
Neat test...and bright!

Wires from coil to distributor look good.
Ground wires motor to chassis look good but I added another anyway linking white(12v power is pink) wire of coil to chasis. Hope that was ok to do to ensure good coil ground?

I have bought yet another new cap and rotor to try next
but feel like I am at a dead end.
Any other suggestions would be appreciated.
Thanks.
Eric

Answer
Okay you lost me on the linking the pink top chasis ground? Not good if you did that you blew the fuse for the coil. The The pink wire is power the white is ground. The white you can run to the chasis not the pink...

How did you tstes the coil?
The pickup coil in the distributor has the proper resistance.
So as long as the distributor is turning when you crank the engine this car should have spark. In not the issue is in the distributor somewhere.. You seem to have covered all your bases pretty well here.. Like I said in the previous post are you sure the part to got for this are for the correct year make an model car?


You may want to try a google search for the symptom you have of no spark and you may find someone somewhere has posted a trouble fault tree to follow for the issue you have with that car.. Just a though. Our service manuals on the net only go back to 1998 So I can't cut and paste you anything for that old of a car.