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Engine run-on

EVOrider

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1983
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The stator inside the distributor bit the dust about six months ago on my stock 1983 Ranger still with the TFI. I went ahead and replaced with a remanufactured distributor. The TFI is motorcraft and is remote mounted on the fender.

The problem is...once the engine is hot and has been running for awhile. Shut the engine off and it continues to run for about a second or two (diesling). Also, once it is hot...it sometimes is slow to start.

It seems this all started when I installed the distributor. I timed it with spout disconnected and 10 degrees BTDC.

No computer codes at all and the truck runs good without any pinging.

Any suggestions....
 


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RonD

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Carbon build up in the cylinders can retain heat after spark is cut off, this could cause the "diesel effect", especially if carb hasn't been rebuilt in awhile.

An engine is an air pump, it pulls air in via the intake manifold and then pushes it out via the exhaust manifold.
A carburetor works by air flowing past the jets, this air flow pulls gas out of the jets as it passes.

When you shut off a carbureted engine, only the spark is turned off, so air flow continues until crank stops spinning, so gas is still pulled from the jets.

"dieseling" occurs because of compression and heat(how a diesel engine works :)).
Carbon build up does two things, it increases compression as it builds up on the piston top, valves and head, it also retains heat as it insulates the cylinder from the cooling system.
Higher compression and heat retention = dieseling with 87 octane fuel.
Yes, pinging could happen as well but that would depend on the timing of the spark.
Fuel injected engines don't have this issue because fuel is cut off as well as spark, that's how diesels are turned of, fuel is cut off.

Higher octane fuel has a higher combustion temperature, that's what the Octane number means, higher number = higher temp needed to self ignite.

Carbon build up comes from running engine rich over a long period, so probably a carb issue that would need to be addressed, along with cleaning out the carbon.

I have never done an engine running carbon clean up but many here have and say it works, you need to do it a few times and be VERY CAREFUL.

Short term would be to run higher octane or a 10% ethanol mix, that raises octane.

As far as the restarting issue, if carb is running rich it could cause a "flooding" effect just after it is shut off, so if you try to restart right away the engine is flooded and has to clear out the raw fuel before it starts, if you let it sits the fuel evaporates, so no issue on restart.
 
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Frank The Tank

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Unhook your PCV valve.... See if that fixes it (temporarily) I had to delete the PCV valves entirely on one truck and put scavenger tubes on.

Too much advance can cause it.

Running too lean or too rich also.....
 

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