1968 GTO Resto-Mod

[fbrown540]

The key not turning the engine off actually happening fairly frequently back in the day when these cars were fairly new. The cause is generally a feedback loop that keeps powering the ignition. You can test for this by simply unplugging the wire to the alternator. If the engine stops with the key off and by unplugging the alternator wire, you have a feedback loop.

If you have a feedback loop, You could leave the alternator unplugged while you trouble shoot the high idle rpm.

Some causes are:

- lack of a resistor in the GEN light line.
- not properly converting the wiring when swapping from an external to internal regulator. This seemed to happen to many of my friends back in the early 70's.
- improper conversion from a points type distributor to a electronic one. Again this happened to many of my friends.

It been so long that I don't remember what was done to fix the problem, but the fix was very minor in all cases.

I don't know if this applies to your engine, but many GM engines of the 60's had a thin metal plate between the carb gasket and the manifold. Leave the metal plate out and the engine won't idle. I had seen many of my friends leave the metal plate out and couldn't get their engine to run very well.

Maybe someone with more recent experience will chime in.

[PBarkley]

Subscribing to this thread...and seeing your recent engine-related post has me on high alert for the same reason with my car, haha.

Glad to see another build staying Pontiac powered!

[1968 GTO Resto-Mod]

Originally Posted by fbrown540

The key not turning the engine off actually happening fairly frequently back in the day when these cars were fairly new. The cause is generally a feedback loop that keeps powering the ignition. You can test for this by simply unplugging the wire to the alternator. If the engine stops with the key off and by unplugging the alternator wire, you have a feedback loop.

If you have a feedback loop, You could leave the alternator unplugged while you trouble shoot the high idle rpm.

Some causes are:

- lack of a resistor in the GEN light line.
- not properly converting the wiring when swapping from an external to internal regulator. This seemed to happen to many of my friends back in the early 70's.
- improper conversion from a points type distributor to a electronic one. Again this happened to many of my friends.

It been so long that I don't remember what was done to fix the problem, but the fix was very minor in all cases.

I don't know if this applies to your engine, but many GM engines of the 60's had a thin metal plate between the carb gasket and the manifold. Leave the metal plate out and the engine won't idle. I had seen many of my friends leave the metal plate out and couldn't get their engine to run very well.

Maybe someone with more recent experience will chime in.

Originally Posted by PBarkley

Subscribing to this thread...and seeing your recent engine-related post has me on high alert for the same reason with my car, haha.

Glad to see another build staying Pontiac powered!

cheers guys- thanks for your input.
i really appreciate your comments!



the engine is running smooth tonight.
next time i should remember to verify correct throttle cable adjustment before start-up!
today i replaced the spark plugs and it started back up no problem.
still need to troubleshoot key not turning the ignition off.
also, there's a small coolant leak at the top of the water pump gasket and a small power steering fluid leak at the pump high pressure line out.



despite a few interesting unexpected challenges recently i've been making some good progress.
i'm happy to know the machine will run.
thank you for having a look at my project!
danny

[waynieZ]

Good to hear it's running good now. With the other posts you'll have some where to start looking for your run on problem.

[PBarkley]

I'd have to go back and look at your ignition setup, but I'm in the process of familiarizing myself with the MSD 6AL box I'll be installing (eventually) on my car and it mentions engine run on, similar to your situation when using the MSD box with a GM HEI distributor. Basically describes that there is some sort of signal that must be bypassed, otherwise the MSD box continues providing spark. Kinda leading me to just do my engine break in without the 6AL and wire it in afterwards.

Never know, but it might be a good place to start your gremlin hunt.

[1968 GTO Resto-Mod]

Originally Posted by waynieZ

Good to hear it's running good now. With the other posts you'll have some where to start looking for your run on problem.

thanks, wayne! it felt so good to see and hear that thing running smooth... for the first time in over 10 years!

Originally Posted by PBarkley

I'd have to go back and look at your ignition setup, but I'm in the process of familiarizing myself with the MSD 6AL box I'll be installing (eventually) on my car and it mentions engine run on, similar to your situation when using the MSD box with a GM HEI distributor. Basically describes that there is some sort of signal that must be bypassed, otherwise the MSD box continues providing spark. Kinda leading me to just do my engine break in without the 6AL and wire it in afterwards.

Never know, but it might be a good place to start your gremlin hunt.

thanks, peter! i've installed msd's pro billet distributor for v8 pontiac application.

the last time i started the engine there was a real high pitched squealing sound for about 5 seconds then it stopped and everything sounded fine.
after i killed the iginition i crawled under the car and saw that the pinion gear had been stuck in the engaged position after the engine started and the ring gear completely shredded it- spun it right off the starter motor output shaft.



i pulled the starter off, boxed it up, and sent it back to robbmc.
those guys are great... they said it's a pretty common problem and that they would be happy to fix it- no problem.
they also said it usually results from a problem with the wiring.
since then i've been doing a little snooping around in the dash wiring and i happened to find a ground wire that i failed to tie into the master ground kit at the firewall.
my hunch is that it provides ground to the ignition switch.
i wonder if this array of problems could have been caused by an improperly grounded ignition switch?
anyway, i'm going back through the wiring starting at the switch and having another close look at the wiring diagrams as well.
my hope is to have the wiring thoroughly inspected and to get any issues resolved by the time the starter gets back to me.

later today i'm meeting with straatsma to talk about the paint job.
he's going to look at the car and hopefully offer some advice regarding fitment/gaps/etc.

always moving forward!
thanks for your interest in my project, and thanks for having a look at this thread!
danny

[PBarkley]

Sounds like you're onto something! Good luck with the hunt!