1976 Pontiac Firebird stops after a while

Tiny
ROGEREDEN
  • MEMBER
  • 1976 PONTIAC FIREBIRD
  • V8
  • 2WD
  • AUTOMATIC
  • 220,000 MILES
My firebird runs great when first started, it warms up and all the thermal sensors work good. It will run for about 10 to 15 min and then it will die like a rock-no spit or sputter-- just quit. I can turn the switch and it starts right back up for maybe 3 min--I can keep doing this for 3 or 4 times and each time it dies faster, and after a while it won't start at all unless I let it set and cool off.
In the past 6 mo I've replaced the carb, egr valve, plugs wires --one year ago cap and rotor.

with all this I'm at a loss why it just dies when it gets hot, it doesnt over heat!
There is an electronic modul in the distributor, if this goes bad is it possible it can open and close some how to creat this problem? Thanks for your help!
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Tuesday, June 29th, 2010 AT 6:36 PM

1 Reply

Tiny
CARADIODOC
  • EXPERT
Hi rogereden. Welcome to the forum. Heat is the deadly enemy of anything electronic and the module is a perfect example, but an even more likely suspect is the pickup coil around the shaft of the distributor. The first thing to do is get it to stall, then verify it is losing spark. Plugs and wires will cause a misfire, never total stalling and a failure to restart. A fuel-related problem won't cause instant stalling. It will lose power and sputter over a period of a few seconds as the float bowl in the carburetor runs dry.

One important thing to be aware of with GM's HEI distributor is it is capable of developing such a high spark voltage, if you interrupt the path by moving a spark plug wire too far from the engine so it can't jump the gap, the spark WILL find a way to ground, and that will be through the rotor. That will leave a carbon trail which will become an easier path for current to flow through than the spark plug gap. That's called "punch through". The symptom will be a no-start condition due to the shorted rotor. To avoid this, just don't hold the spark plug wire more than about 1/4" from the engine when looking for spark.

The pickup coil can be tested with an ohm meter while wiggling the leads. If you replace the module, be sure to use heat sink grease between the metal surfaces for good heat transfer.

Caradiodoc
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Tuesday, June 29th, 2010 AT 7:17 PM

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