Hello,

First before I talk about my starting problem, let me wish all the texan members of the forum my best wishes and hope you all get thru safe from the terrible weather conditions you are suffering right now.

Now for my problem:
Some months ago I posted a thread about my engine cranking but not starting, I got plenty of posts that I followed and until about a month ago I though the problem was solved By the way, I own a corvette 1979 L82 4 speed mechanical.
The actual problem is:
The engine cranks but doesn't start,
I changed the spark plugs and wires (MSD),
I changed the distributor HEI (made in the USA, not china, it delivers 50000 V instead of the 35000 V standard,

After all this the car started fine for a couple months.

Now the car doesn't want to start.

I turn the key, the engine cranks but no spark (I use my timing light to check, its easier than pulling a plug ) . I have 12,38 V at the distributor when I crank the engine (goes down to about 8 V during cranking).

After removing the distributor cap and looking around inside (tapping with my finger on anything that I saw (or dare move )), the engine started no problem. I checked the initial timing and set to 8° before TDC (which I checked before). The car runs great.

Now this evening I tried starting it and nothing no spark no start. I'm tired of removing the distributor cap so I took a hammer (not a sledge hammer ) and tapped on the case of the distributor, just a couple of times. And guess what ? the engine started right away but very bad idling (even stalled on me).

Please help, what's wrong with my car?

My ideas just in cas,

Going bad (or bad) ignition module,
Going bad (or bad) pick-up coil (hope not, not easy to change).

Any suggestions would be welcome.

Thanks to all

 

That is strange. Loose wire? but I'd think driving would make it "loose" again causing driveablility problems. Something in the distributor grounding out?

 

Thanks for answering

Can't see anything loose inside distributor. And the hard start (if not impossible if I don't tap the bottom of the distri) has happened again after a few months with no problem.

 

The "tap" solution is what is getting me. There has to be something loose that the tap is temporarily fixing. Are your advance weights sticking?
Maybe try starting it and when it doesn't start don't tap then remove the distributor cap and look around.

 

Well you are a true investigator and narrowed it down to the cap. Let me tell you about something in that HEI cap that gave me trouble. Under that dust cover, as you know is the coil. That coil frame has a shiney coating, almost a paint to keep from rusting. One wire connects to that frame on one of the corners with a screw. Take that off and wire brush that coating off the coil frame, reattach the wire. It has to have a good ground.

And while you're in there, check the spring button under the coil for corrosion. I think one of those two is the problem.

 

Thanks,

Well the distri cap with the coil are brand new (Made in the USA, not China or so says the label ;-)). I checked the button and cleaned it. The advance weights work fine. From what I read in other posts I still think it could be the module, but then can it go bad for ten minutes and then work again ?

 

Next time it won't start, remove the TACH wire from the cap and try that. If still no start, connect a 12v test light between that TACH terminal and a good ground. Watch the light while you crank. If the module and pickup coil are both "doing their job" the test light should flash while cranking. Might help narrowing the possibilities a bit.

 

One thing you could try, use a test light and ground the lead, put the probe in the tach terminal in the cap and crank it. You should see the test light flash if the module is working.

Another thing to try is unplugging the tach wire and see if it starts, could be an intermittent problem with the tach wiring.

 

Guess I wasn't typing fast enough!

 

Thanks,

I sure learned something with you both this evening (very well synchronized answers I might add). I didn't know I could test the module and pick up coil with a test light. I'll go to bed less dumb tonight). I'll check tomorrow, I have to buy a test light and here its midnight so too late to go shopping.

 

I'll let you know tomorrow the result of this test.

 

The small power wires may be loose I've had to tighten mine

 

Well sorry, bad luck my car started at the first turn of the key (it never started that quickly before), probably got scared when it saw me coming with all the wiring (home made at work test lamp). But I don't despair I know it will not start as soon as I turn my back. As for the spark plugs they are new and when I last pulled one out (couple of days ago) it still looked like new.
As for the small power wires, I'm not sure I know which wires you are mentioning and where they are located, can you explain.

Thanks to you all

 

The pins in the connector that plugs into the distributor would be my guess.

 

Thanks, I'll check them.

 

may try adding dielectric grease on there also, should help promote conductivity and prevent moisture from getting in.

 

Well thanks but doesn't dielectric mean electrical insulation not conductivity. Some times back I read a big debate on this forum about the use (or not) of dielectric grease on electrical contacts, still not sure about the conclusion of this debate.

 

Actually it is a non-conductive grease to keep moisture out and if it's in a switch to lube the moving parts. You are correct.

You could check to see if the pins have "opened up" and not making good contact. I've seen that over the years on the semiconductor systems I work on for a living.
The next time it doesn't start just go to that connector before doing anything else and move it around a little and see if that helps.

 

You are correct, dielectric means its an insulator.

 

guess thats what i get for not paying attention to its function. Learned something new.