Engine cuts out and stalls while driving.

enkeivette

enkeivette

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Mar 30, 2008
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Blown 383 SBC, Annular Mighty Demon 750 Carb with an MSD HEI.

Car idles ok, but as the RPM builds, the motor cuts out completely and stalls. Seems to be independent of throttle position, and only RPM related. Car restarts after stalling.

What is the cause?
 
big_G said:
Running out of fuel?
Click to expand...

Bowls are full, up to the top line in the sight glass window after stalling. Fuel pressure guage reads 7psi at atmospheric level. Fuel filter is relatively new.
 
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A long time ago, I had a similar problem on a car I bought. Clogged fuel filter (Q-jet sintered inlet filter). It would run great until you ran the bowl dry and then it would just die. Re-start, and it was just fine.

Edit: just saw your response to Big_G. Looks like a clogged filter isn't it.
 
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If it's unrelated to throttle position and purely rpm related I'm thinking it's an ignition problem.... bad coil or module ???

Edit: a few years ago I had a very similar problem with a V6 Camaro... different ignition system and EFI but the same symptoms... it was the ignition module (unfortunately a lot more expensive than the entire dizzy for a C3)...
 
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BBShark said:
A long time ago, I had a similar problem on a car I bought. Clogged fuel filter (Q-jet sintered inlet filter). It would run great until you ran the bowl dry and then it would just die. Re-start, and it was just fine.

Edit: just saw your response to Big_G. Looks like a clogged filter isn't it.
Click to expand...

Bowls are not running dry, I'm sure.
 
did the engine run in the current configuration ? I'm asking just to make sure that this is related to a failure of one part and not caused by a change that you made - for example a new distributor or a different jet size.
 
enkeivette said:
Blown 383 SBC, Annular Mighty Demon 750 Carb with an MSD HEI.

Car idles ok, but as the RPM builds, the motor cuts out completely and stalls. Seems to be independent of throttle position, and only RPM related. Car restarts after stalling.

What is the cause?
Click to expand...

Is the distributor an inductive ignition (like an actual HEI), or is it a CD unit attached to an HEI appearing distributor?
 
MYBAD79 said:
If it's unrelated to throttle position and purely rpm related I'm thinking it's an ignition problem.... bad coil or module ???

Edit: a few years ago I had a very similar problem with a V6 Camaro... different ignition system and EFI but the same symptoms... it was the ignition module (unfortunately a lot more expensive than the entire dizzy for a C3)...
Click to expand...

I think so too, doesn't seem to be a fuel issue. What should I check?
 
Arthur Brown said:
did the engine run in the current configuration ? I'm asking just to make sure that this is related to a failure of one part and not caused by a change that you made - for example a new distributor or a different jet size.
Click to expand...

Yes, engine cruised at 14.5:1 AFR cruise and 12:5:1 WOT under boost. No changes have been made.
 
69427 said:
enkeivette said:
Blown 383 SBC, Annular Mighty Demon 750 Carb with an MSD HEI.

Car idles ok, but as the RPM builds, the motor cuts out completely and stalls. Seems to be independent of throttle position, and only RPM related. Car restarts after stalling.

What is the cause?
Click to expand...

Is the distributor an inductive ignition (like an actual HEI), or is it a CD unit attached to an HEI appearing distributor?
Click to expand...

It's an actual HEI.
 
IMO, since you seem to be sure it's getting fuel the quickest and easiest "test" is to simply replace the entire dizzy with a known good unit, do you have the old dizzy (you say it's a MSD HEI) ??? ... maybe you can borrow one ?? ...

You're saying the engine ran fine before and no changes have been made... sounds like something failed.

On the fuel side: the filter could have bursted and dirt/debris could have plugged the jets... well, this is not very likely.... anyways, check the filter just to rule it out ...
 
Is this happening just sitting or on the road under load or both?

Does this happen both when the throttle is opened very slowly to rpm and/or when quickly floored.

Does your hei have vacuum advance?

Just having 7 psi fuel pressure doesn't mean the gas is getting thru the filter, a mostly blocked filter will will also give pressure readings and your symtoms, but more so on the road under load.

An easy way to test for spark at any rpm is just to run with a timing lite connected. Mine has leads long enough to operate while driving.
 
I'd say you have water in your filter but that doesn't rhyme with the fuel bowls being full after stalling. Does it backfire? That would indicate a lean mixture.

Need to know what exactly you have complete fuel system & ign system
 
enkeivette said:
69427 said:
enkeivette said:
Blown 383 SBC, Annular Mighty Demon 750 Carb with an MSD HEI.

Car idles ok, but as the RPM builds, the motor cuts out completely and stalls. Seems to be independent of throttle position, and only RPM related. Car restarts after stalling.

What is the cause?
Click to expand...

Is the distributor an inductive ignition (like an actual HEI), or is it a CD unit attached to an HEI appearing distributor?
Click to expand...

It's an actual HEI.
Click to expand...

So, do I understand you correctly that it is an MSD copy of a GM HEI distributor (an inductive ignition), and NOT a capacitive discharge system with an external oscillator box hooked to the distributor?
 
Problem - Spark plug wire melted and shorted on header.
 
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