Engine stops running

[mgtdsteve]

My 1978 has developed a strange problem after driving for about 20-30 mins. the engine shuts down. After it sit for about 10 mins. it starts and runs again but it quits again. So I have some questions about this issue.

1. As the car has a closed fuel system, I unscrewed the cap and drove the car for a while and it didn't quit. Could this be the problem?

2. I have a fuel filter that you can see the gas inside. when you turn the car off the filter drains back to the inlet level. Normal or does this indicate a bad pump.

3. My Chevy hot rod friends said, a likely cause would be the HEI system. Replacing the electrical parts bought separately cost more than a whole new one from Summit. What are the chances this is the issue.?

4. Any other ideas? thanks, Steve

[Gunslinger]

It's possible it's the module inside the distributor cap.  They're easy to replace and widely available.  You could buy one at Pep Boys, AutoZone, NAPA or else where and it will either do the trick or not...they're not expensive so it's something to try.  I had a '78 Corvette that needed a replacement after thirty years so it could be the cause.  You don't need a high performance module...a factory or factory equivalent module is all you need.

 

 

[Avanti83]

As with a previous thread, I always like to start with gas flow when these things happen. Your gas cap clue could be the issue with a plugged/non-functioning cap vent. You might want to drill a small hole in the cap and see if the issue continues to goes away and then replace the cap. Be sure the hole isn't covered by the gasket. 

I'd also check for where the gas filters/filter are and replace them. If the issue continues after that, a bad rubber gas line could also be the cause.

I'm not discounting Gunslingers comments on the module as heat soak can cause this problem also and those modules should be pretty inexpensive by now.

So far the cost has been pretty low, if it continues - you could replace the pump, add a fuel pressure gauge or find a shop that deals with older Chebby power and see what they think.

[Ron Dame]

It seems you may have answered your own question by leaving the gas cap loose. Keep doing this and see if it stays gone, then address your vent system if it does.

Did you loosen the cap last time it died and hear a whoosh? If so, that is certainly your problem

Edited June 17, 2018 by Ron Dame

[mgtdsteve]

Thanks for the help. If you replace the fuel pump is the pump rod normally replaced ?

[Avanti83]

4 hours ago, mgtdsteve said:

Thanks for the help. If you replace the fuel pump is the pump rod normally replaced ?

If it's been pushing since 1978, it's probably a good idea to replace it. With the price of most SBC parts where they are, I usually replace anything that moves a lot.

One tip, if the pump rod keeps falling out as you install the pump, add a dollop of grease to the rod as it's almost seated against the cam and push it in the rest of the way.