It's not really an insulator but it's non-conductive. Insulating properties would be counter productive to what it's doing. But lets stay on topic to help the OP with his problem.

 

Thanks to all for your help so far. I'll try again tomorrow to not start my vett (unless it lets me down and start like it did today). Hard to find the source of my starting problem if the car keeps starting ;-)) I want to put to use all your suggestions but my vett doesn't me.
This is the worth kind of problem, its here than its not, imagine if I take my car to a garage to tell them it doesn't start, their first question would be: if it doesn't start how did you drive here and their second would be we didn't find any problem, starts every time (I know the first time it happened I took it to a local garage (first V8 he saw) and the car started every time, well until I drove it home and then it didn't want to again).
I'll let you know tomorrow the verdict.

Thanks

 

I understand your frustration. Just keep after it..

I would never find the real source of the problem. I'd be in there ripping everything-- EVERYTHING! apart, checking all the parts and going through the whole system with a currycomb. Then put it all back together and dare it to happen again.
I was working on an older ford (I know- family member) that had an intermittent no start. Fooled with that thing for 2 weeks until it finally showed me the problem. New crank sensor and done.

 

Hello american friends,
So the latest news. My car once again started at the first turn of the key (can't explain that one). The only thong I did since it let me down last week is:
1. Once started, I reset the timing to 8° before TDC as written in the tune up book (for a 1979 L82),
2. When it didn't want to start (again) I tapped with a (very small hammer) the metal part of the distributor (on the side where the vacuum advance is located).

Well since then it starts no problem. I have a few questions about the timing.
For timing I disconnect the vacuum advance and plug it, but then the engine lost rpm (it goes from 900 rpm at idle down to about 600 rpm), question is this normal for the idling speed to go down with the vacuum advance disconnected.
I set (at 600 rpm) the timing at 8° before TDC (as asked in my maintenance book). The car once everything connected runs OK but could be better.
Today I checked the timing at idle speed (900 rpm) and it is at 12° before TDC. Question should I put it back to 8° at 900 rpm or keep there.
I have read on this forum and on many other website that what is important is not initial timing but total timing and for my engine (350) it should be set to 36° before TDC at 2500 rpm. Question, if I do that wouldn't my initial timing go up (already at 12° at 900 rpm) and damage the engine or cause backfire.
Right now the engine starts, is there a risk that it doesn't if I change the timing again.
Last question, could tapping on the side of the distributor be the reason for the engine starting at first try or do you think it is only a coincidence.
Thank you

 

IF it cranks and starts fine with the initial timing at 12-14* I'd go with it. You won't hurt the engine. The only thing is if the timing is advanced far enough it "kicks back" at the starter when cranking. If I does, drop a couple of degrees and try again.

I'm sure this has been asked and answered, but you have made sure the mechanical advance weights under the distributor rotor are free?

 

Sounds like your vac advance can is plumbed to manifold vacuum that is the reason for your RPM increase when it's connected. Not sure if that's the way it's suppose to be on a '79.
You should set your timing with it disconnected. Total advance should be checked with it disconnected. Vac advance is for part throttle use like at highway speed cruising to aid in gas mileage and to keep the engine temp down a bit. If your total all in advance is 36 the vac can should only give you 10 to 12 more degree. Anything more than that and when you accelerate from an off idle throttle position you're probably going to get some pinging.
What kind of timing light do you have. Is it the adjustable one with the dial on the back? It's much easier to use one of those for all timing conditions as most SBC timing marks don't go much above 20 degree on the balancer.
Since your 'no-start' condition has gone away it's hard to pinpoint the cause. I know your feeling, it will start for months but the minute you start forgetting about it it will come back. Intermittent problems are the worst.

 

Thanks, and yes intermittent problems is like having the sword of Damocles over my head.
My timing light is not of the dial in type but I think I should buy one because my balancer only has the initial mark (white line) so to advance to 36° is not possible without adding some graduation.
As for the 12° I have showing right now at 900 rpm it is with the vac advance not connected (when connected the timing mark is too unstable to make a good reading).

 

Hello,
Well this evening I took my vett for a ride and it worked great, from starting all the way thru the ride and back. I just hope it keeps going, I have a meeting of corvette in 3 weeks (about 40 corvettes expected, from C1 to C7).
I might (I'm sure) will need your help on some other (less important) problems I have with my vett.
Again thanks for everything

 

Hello its me again,
Well today the car didn't want to start (4 days without a problem), but at least it gave me the opportunity to use the test lamp connected to the tach connector. Here is what happened:
1. when I crank the engine the test lamp is on and the light doesn't flash,
2. Like I did before I used a hammer to tap on the metallic part of the distributor (below the cap),
3. I cranked the engine and the light flashed very rapidly,
4. I had to remove the test lamp (probably draining too much current) and the engine started no problem.
Now I know for sure the problem comes from the distributor, but where. Is it the module or the pick up coil because I don't see much more down there and I know the weights work fine.
Can I ask for your help again because now I'm out of ideas.
Thanks

 

8V during cranking might not be enough voltage to reliably operate the distributor. However, the tapping fixing it doesn't fit with that being the issue.

 

Before I tapped on the ditri the test lamp was steady but very bright so I had the 12 V. I still think the module or the pickup coil are not doing there job. Just in case I ordered a new module.

 

With the light connected to the TACH terminal, and not flashing when you crank, there is a problem with either the module or pickup coil. You stated you have a module coming, when you replace it, very carefully check the wires and connectors to the pickup coil. Check for cracked insulation, dirty connector, broken wires. Also make sure to put the heat conducting grease on the module or on the distributor where the module sets.

 

Thanks for the information, I'll check everything when I get the module. I never changer a pickup coil before, can you tell me if it is hard to do. Where I live there is american car specialist (at least not near me), I have rebuilt engine before (when I lived in the US) but never had to work on a distributor.

 

While replacing my coil I noticed that paint and wondered how it could get a decent connection through it