naf

iTrader: (7)

I've had an infrequent, random no-spark on start up issue with my 85 stock LG4. The first time I assumed heat soak and allowed it to cool for a while and it started fine. Purchased a new GM control module and coil. Swapped the coil in and held on to the control module until it did it again about a month later. Swapped control modules out in the parking lot and it fired up. Cap, rotor, plugs and wires were new already a few months before when I bought it. Since then over the past year and a half it's probably done it to me 6-7 times. I either wait twenty minutes or so or swap control modules and it fires right up. It's done it to me twice first thing in the morning so I'm thinking it's not a heat soak issue. I've pulled the Fluke out twice when it's failed to spark and verified voltage to the coil. I'm not sure why swapping control modules would fix it as I've only got the two and just flip one for the other. I'm thinking a loose connection in there somewhere would manifest itself in other ways too, but I've never seen any indication of mis-fire or ignition failure while the engine's running.

Any ideas or things I can check the next time this occurs? I'm not as familiar with the workings of the ESC system as I'd like. Does it control spark differently during start? Other than the timing?

five7kid

iTrader: (14)

You've already replaced the two most usual suspects. The third is the pick-up coil assembly, the piece that sits around the trigger wheel on the distributor shaft.

Poor connection is a possibility, and you're "fixing" it by swapping the module. More likely the act of opening up the distributor lets it cool down enough to start when you put it back together. But, it might be a corroded terminal that gets cleaned a little while you're swapping.

naf

iTrader: (7)

I'm thinking poor connection as well but don't know where to go next time to trace it down.

I know it's not a heat issue though as it did it to me this morning after sitting in the garage overnight at around 50-60 degrees.

five7kid

iTrader: (14)

It could still be the pickup coil.

But, going through and cleaning up all the electrical connections would be a no-cost task.

The only time my car did that to me was when the distributor power wire had slipped out of the cap. You know, the age-old busted plastic clip thing.

naf

iTrader: (7)

The previous owner had a new distributor put in bout a year before I got it. I'm wondering if this problem didn't exist then and the new dist was some shop's solution.

I'll probably pull all of the wiring to the dist/module out and rebuild those small harness pieces best I can. Know of a source for the little clips?

If it does it again I may try to fire it with the four-wire connector disconnected. That would take the ESC (or is it EST) out of play, maybe?

five7kid

iTrader: (14)

I don't know of a good source for the terminals other than the universal stuff.

I doubt removing the flat 4-wire will do much. Just affects timing. I know mine is harder to start with it disconnected.

If the distributor was replaced with a real new one, that takes out most of the candidates (depending upon how complete the new distributor was).

Some random thoughts:

Check all of the connectors under the coil cover. Make sure the ground wire is under the coil mount screw (probably is, since you changed the coil). Make sure all of the blade terminals are in straight and fully seated.

Check all other connectors and harnesses for looseness, corrosion, shorting.

naf

iTrader: (7)

I've been pondering and it seems that a loose connection bad enough for it not to start would probably be noticed at other times. I'm thinking it may be a problem that is only evident at start or is exacerbated by starting. Two things that come to mind that are different when starting and regular running are the lower voltage during the start cycle and the lack of electronic advance. That's why I was curious about the operation of the electronic ignition control system.

If I'm thinking in a wrong direction set me back on track.

Yes when I changed the coil I found the other one had not been properly grounded. Really thought maybe I had discovered something and that's why I waited for the problem to reoccur before swapping the module. AC Delco module +$50 bucks, GM Parts Direct, stamped GM on one side and Made in Singapore on the other. Go figure.

Dist was replaced, I saw the receipt, but new, rebuilt, found in an old car out behind the shop? who knows.

Thanks for the advice.

naf

iTrader: (7)

Just to update (and to see how long since it did it last) had a no-spark last week after sitting hot in a parking lot for about 20 minutes. Pulled the cap and only wiped down the rotor tip and cap 'trodes. Instantly fired back up. Rotor was a little dusty with carbon. Dist parts weren't particularly hot.

That's six months and around 8-9000 miles between events. Maybe an annual cap/rotor change combined with a light cleaning every oil change.

naf

iTrader: (7)

New cap and rotor no good. Replaced distributor a few weeks back (after hanging around after a class for 45 minutes for the car to start), will wait and see.