1972 F Engine runs too well

mrboatman

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you still have power to the + side of coil
 
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That’s how I disconnected the ignition, I pulled the wire from the coil.
I did some Google research.
I reckon I have some carbon on the pistons/head causing hotspots allowing the engine to “ Diesel“.
Before pulling the head to scrape said carbon, I’ll try high-octane fuel and install an idle stop solenoid on my weber carburetor.
 

pjohnson

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Use your Google-fu to research ALL the causes of dieseling. Your proposed actions won't resolve the issue.

Hint: start with timing...
 

Steamer

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How well does it keep running? Smooth enough to drive or is it shaking, pinging, and making other strange noises?

If it has the stock carburetor, make sure the idle cut off solenoid is functioning and that someone did not raise the idle speed way up to compensate for it not functioning.

A few pics of your engine bay and a video of the occurrence with sound would really help avoiding a lot of back-and-forth Q&A and get more direct to a diagnosis.
 
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You’re right, my initial description was vague.
This is a project truck that I’ve just acquired and never driven.
The run on is not smooth, sputtering and struggling… very much dieseling symptoms.
It idles at 600 RPM.
Ignition timing can’t be an issue because I’m disconnecting the hot side of the coil, there’s no spark at all.
 
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You’re right, my initial description was vague.
This is a project truck that I’ve just acquired and never driven.
The run on is not smooth, sputtering and struggling… very much dieseling symptoms.
It idles at 600 RPM.
Ignition timing can’t be an issue because I’m disconnecting the hot side of the coil, there’s no spark at all.
So it does the same thing if you just turn the engine off with the ignition key?
 

pjohnson

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You’re right, my initial description was vague.
This is a project truck that I’ve just acquired and never driven.
The run on is not smooth, sputtering and struggling… very much dieseling symptoms.
It idles at 600 RPM.
Ignition timing can’t be an issue because I’m disconnecting the hot side of the coil, there’s no spark at all.
This statement is completely inaccurate. The term dieseling refers to the fact a diesel runs with no spark whatsoever, which is exactly what you have taking place.
 
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If you have dieseling on a gas engine you will hear pinging and knocking with a rough idle and the engine eventually stops running.
If it keeps smoothly running with key off then you are still getting electricity to the coil somehow.
Years ago I had an electric radiator fan that I hooked up through the ignition wiring.
When I shut the engine off it would keep running for a few seconds as the still spinning fan became a generator and fed power to the coil.
Then there was the time I decided to run the ignition switch trough a relay to get a clean full 12 volts to the HEI I had installed.
When I turned the key to off, the coil was still getting juice and the engine kept running.
Never figured that one out, just stayed with the old hook up.
If you are getting dieseling don't let it go before you knock a hole piston.
 

middlecalf

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What's the main timing culprit wrt dieseling, too much advance or too little?
 

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