Vette(s): 1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c
brian, there should have been a small packet of the dieselectric grease in with the module. besides transfering the heat i believe it also helps conduct the currents thru it. when you remove the ignition module make sure to clean the plate wher it mounts and the bottom of the module good. coat the plate with a very thin layer of the grease and reinstall the module. hope this works for you.
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To test spark at the plug terminal at the distributor remove sprk plug wire at the distributor.... have a test light, and a wire with clips on each end.
Attach the wire to good ground (alt ground) take the other end of the wire and connect it to the test probe of the test light. with someone cranking it over bring the probe with the ground wire attached close to the terminal and see if you have a spark. Be careful only hold the handle part of the test light (wear some rubber gloves if you have some), or you can try to rest it close while you turn it over.
I don't think you have the tach wire connected, if you do disconnect it,
Also when the coil or distributor cap is replaced, check that the ground clip is transferred from the old distributor cap to the new one. Remember there are two designs of HEI coils. One uses red and white wires, whereas the other design uses red and yellow wires for the primary coil that are reverse polarity be sure to get the proper one in the proper spot.
When you put the coil in ....you did put the spring loaded button on the bottom that touches the rotor right? If you can maybe take the coil out take it back where you bought it and have them test it and take your old one with you and have them test it too....if the old one is good this will help/seperate to find the problem.
Problem found. I was reading through all the posts & figured I'd run through all the tests again. When I went to test the tach cord, I didn't like the results I was getting, according to Kstyer's post. So, I disconnected the tach clip from the distrib & tried to start. To my surprise, she fired right up!!!! Yee Haw!!! You all deserve a big round of applause. You are all ok in my book. Thanks to everyone for helpping solve this problem. If any of us ever meet up, first couple rounds are on me.
Now I just have to find where the tach cord is not grounding properly. But at least I know where the problem is & where to start.
I had the same problem with my 1981 350 L81, no spark and would not run. It had previously died randomly and then finally would not start at all.
During the process of returning the car to service after 31 years in storage, a new ignition coil was installed in the HEI ignition. There are two grounds on the coil, one on top of the coil where the black wire attaches and the other is on the bottom of the coil where it grounds to the car. The new coil had a thick paint coating on the metal plates which was not removed in the two ground lug areas. Once the paint was removed in the ground lug areas, the car started and ran fine.
What I think was happening was the ground lugs had just enough of a ground in the painted areas to let the car run intermittenly but would occasionally loose the ground and the car would just quit. Changing the module, radio supressor capacitor, and rotor had no effect. But when the paint in the ground lug areas was cleaned off, it had a good ground and ran fine.
I now have a sign on my work bench stating "Before you spend any money chasing electrical problems with new parts, make sure the battery is good and all grounds are good". I already knew that but did not follow that advice on this problem, hence the sign.
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