Ok guys I searched the forum but found no help there. This is the situation. The people I bought the car from said it was running and driving fine and it just stopped running. So after getting the car home I tested the ignition module and coil. They were both fine. Then I looked at the pickup coil and it looked suspect. I damaged the distributor trying to replace the coil by itself, so I just replaced the whole darn thing. I still have no spark. All fuses are good. The harness between the coil and ICM is fine. Replaced the coil for the hell of it, still no spark. I have a GM repair manual for this car, so a friend and I went through the diagnostic chart checking everything it says to check and everything checked out fine. I talked to another guy who said that the ECM harnesses supposedly have an issue with some of the wires breaking where they come through the body into the engine compartment. Any truth to that?
From what I understand from reading the repair manual that shouldnt make a difference at this point anyway. Because I should still be getting spark, it would just start up and die, as the computer doesnt do anything with ignition until like 500 or 600 rpm. Another thing that has been bothering me and Im sure will sound very silly. Do these cars NEED the alternator to start or just for running? which is to say I should still be getting spark regardless right?

 

make sure there is 12 volts to the plug on the dizzy that comes out of the main harness, not the plug that goes from dizzy to coil.

also verify 12volts to the coil

the ignition setup does not need the ecm to function at all so forget about the ecm at this point, the only thing the ecm is actually used for is to control the timming, without it the timming will just be locked at whatever base timming is set at by rotating the dizzy and locking it down to set the base timming

btw is the tach in the car moving at all while u crank the engine over?

 

which terminal? theres four wires there right? and there reason I decided to replace the coil is because we were testing it with the car turned on and found 12volts on the coil output. hmmm tach working not sure.

 

ill have to dbl check the terminal for u cant rember off hand.give me a few mins and ill get it

 

im sorry i made a mistake there is no 12volts to the module only a 5 volt lead which is switched by the ecm after the engine reaches a certian rpm .a lack of 5 volts on this wire will not prevent the ignition system from firing pin b will have the 5 volts once the engine fires the 5 volts comes from the ecm

• tach signal is a purple wire with a white trace [pin R]
• advance control signal is a white wire [pin E]
• override (cranking) signal is a tan wire with a black trace [pin B]

the far left pin labeled g is a ground pin

 

soooo what your telling me is I need to look for 5 volts at pin b? until the engine starts and then its controlled by the ecm. so If I dont have 5 volts there there is a problem in the wiring harness right?

 

no u wont have 5 volts there till he engine reaches a set rpm then the ecm applies 5 volts to that pin to control timming

but the ignition system will fire regardless of there is or isnt 5 volts on that pin

for now just see of u have 12 volts at the ignition coil and also make sure u have ground on pin g of the module plug

 

ok so i checked for voltage at the coil on both sides of the "black connector" and saw 12 volts at both terminals. I was unable to get continuity from any of the terminals on the four wire connector to ground. the svc manual lists these as abcd no g. so I just looked for continuity like i said from any of them. no such luck.

 

ur getting 12 volt at 2 terminals on the coil?

 

ok I just double checked and im not getting 12volts at two terminals, im getting 12volts at all the terminals. and yes no ground at "g" terminal

 

sounds liek you have a short ur going to have to peel back all the loom and see were the short is, u should only have 12 volt at one terminal at the coil

 

if I had longer test leads I could just look for continuity to figure out which wire was messed up, of course I would still need to fix it so, is there a bulkhead connector in that passenger side fenderwell or does the harness just go thru?

 

ok so i got it figured out, the problem ended up being a few different issues compounded.
1st the dizzy that I replaced ended up being defective, 2nd the coil was also defective, and 3rd the harness between the coil and ICM ended up being faulty. It had continuity but one of the plugs ended up being the issue. I swapped in the harness from my z28 since it sits awaiting a transmission and voila, she starts. Still having other minor issues but not going to go into them until I get the obvious stuff fixed.

 

I'm interested incase my swap gives me trouble in this area.

 

i will help where and if i can

 

im having similar problem with my 3.1, diz is good, icm is good, coil is good, but still no spark, believe its the harness but don't know which one it is to order, only engine harnesses i seen were for msd upgraded ignitions mines stock if someone could give me a part name and a solution i would be eternally grateful been 6 mos since i had it running and its friggin cold in michigan right now

 

you cant by the harness new, I tried. You will have to find a salvage yard to get one or maybe on ebay. FWIW if you find them in a salvage yard I would grab a couple of them. You don't have to find an F body to get these harnesses, all you have to find is a GM car or truck or round-about the same year. as long as they have the remote coil and small cap distributor you should be golden. If anyone else feels like putting up an interchange list, go for it.

 

Oh and take this for what it is, I work at advance auto parts. It still took me going through two dizzys and two coils, and oh yeah don't forget two ICMs to get good ones. Of course you can ask anyone I know, electronic equipment or any sort and I don't really mesh well if you know what I mean. Of course since I work there there was no hassle getting new stuff.

 

Im having a problem with my 91 3.1.
it rides fine, but when it warms up it will loose spark, i have to pull over put it in park (wont start in neutral) and then start it and then it will do it agin about a mile down the road.
i put it in the shop and they put in a new disributor and its still doin it.
Were both compleatly lost, anyone else had this problem? any ideas?