Intermitted engine shut down - non GM computer

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Nov 6, 2019 | 08:38 PM

shane65

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Intermitted engine shut down - non GM computer

I've got a 72 GMC with a L33 5.3, carb manifold but with a 400 hp Fitech, Edelbrock timing control box. I'm running out of ideas to my problem of the engine shutting down while driving. Always when at normal running temperature and inconsistent when it decides to shut off the engine. It has done it twice in 1 minute then drive for 30 minutes with no problem. When I try to restart if will attempt for a second but not run. I've quadrupled check the fuses, done wiggle tests on the wires. Verified the fuel pump is running, etc... I sent the Fitech back and they installed a new computer. That fixed the engine temperature reading that would max at 185°. Still has the same issue. I had been running the MSD 6014 and it continued with the problem. Switched back to the Edelbrock and still the same problem. So that should eliminate the Fitech and the ignition box. What does work is doing nothing and restart after 5-8 minutes. Fires and runs good but it can and has quit again at any time on the same drive. Pretty unsafe to lose your power steering and brakes and trying to get off the road to a safe area. There are no codes on the Fitech but that's to be expected. The ignition boxes have no code reading ability. I think it's ignition firing related. Could a cam or crank sensor fail intermittingly and return to working again. The cooling down before it restarts is a clue but a clue to what? This has been a very reliable truck. We've driven it 2500 miles to Arizona for the winter twice and once to Florida. Right now a drive into town 6 miles away is a problem.

Nov 6, 2019 | 10:20 PM

G Atsma

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From: Central Cal.

Try a new crank sensor. A cam sensor won't shut it off. You can start it without a cam sensor, it just takes longer.

Nov 6, 2019 | 10:25 PM

shane65

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Can a crank sensor be OK, then not and minutes later be Ok again?

Nov 6, 2019 | 10:36 PM

G Atsma

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From: Central Cal.

If there's a bad internal connection, yeah. It has happened.

Nov 7, 2019 | 08:08 AM

LilJayV10

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From: Evansville,IN

Quote:

Originally Posted by G Atsma

Try a new crank sensor. A cam sensor won't shut it off. You can start it without a cam sensor, it just takes longer.

With a stock PCM this is true. I "believe"remember reading a post within the past week on here that the MSD has to see the cam sensor to run.

Nov 7, 2019 | 10:18 AM

G Atsma

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From: Central Cal.

Quote:

Originally Posted by LilJayV10

With a stock PCM this is true. I "believe"remember reading a post within the past week on here that the MSD has to see the cam sensor to run.

Thank you! I wasn't aware of that. Too used to stock setups.....

Nov 8, 2019 | 10:01 AM

shane65

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I posted yesterday but the post was not posted. Maybe because I had a picture attached. I'm thinking it's the cam sensor and it's a little oily in that area. Not sure if oil contamination can be a factor. I had to use a front cam sensor because I switch to a LS2 cam before installing the L33 engine 3 years ago. White crap has ruined my chance to fix and drive the truck now that the roads are covered in salt. The truck is 48 years old and still has the original paint. Might be a while before everything dries up and the roads are good enough to put some miles on it.