The Stovebolt Site Forums The Shop Area Engine Shop dieseling?

I have recently had a dieseling problem, and today I looked right after I shut off the motor and noticed the top end of the carb was wet with fuel. I am told that fuel continuing to flow down the carb will casue the dieseling, though I'm not exactly sure how, but what is causing it to spill outside the carb? Is there a specific shut off procedure? Manual choke, monojet.
Thanks, Josh

Hy cowinthefog, I was taught that the only way a gas engine could run on after the ignition was turned off was because there were glowing carbon deposits in the cylinder and the engine could still get oxygen past the throttle plate. We can't do much about the deposits but we can control the oxygen by setting the carb up to run with the smallest amount of throttle opening possible at idle. It also sounds like your float level is high, or maybe it's getting gas logged. Hope this helps.

Thanks, I'll check the float setting on Monday.

Some top engine cleaner would help get rid of the carbon deposits. No hot spots, no ignition, no dieseling.

Work the throttle linkage & watch the carb. If the air horn gasket is bad the accccel. pump can squirt gas out the side on a monojet. Running on was a common problem on monojets. Some had a selinoid that let the throttle close almost completely when the ign. was shut off.

It's a reman'd monojet from a 68. I have only had it on the truck about a week and a half. When I shut it off, should try closing the choke plate all the way to cut off the air supply? What I have been doing is, as soon I shut off the ignition I floor it to get the choke step on the linkage out of the way and pull the choke all the way shut. Should I just turn it off and let it chug? It seems to be getting worse. Will this problem ruin my carb, or is it just a nuisance?

I wouldn,t choke it to kill it. If it,s a manual put it in high gear & let the clutch out. If it,s auto matic turn the ign off while it is still in drive. Can you slow the idle speed down a little? are there any vacuum leaks?

Clutch out with my foot on the brake right? Silly question....I can drop the idle speed a bit, no intake leaks, but the exhaust manifold leaks a bit from pitting around the mating surfaces. I should have it machined. Why though, would I get enough fuel out the top of the carb(between the bottom of the air cleaner and the top of the carb) to soak the whole side of the carb? I don't pump the gas pedal but just the once to get the choke cam on the throttle shaft out of the way to pull the choke shut. When I was doing it that way, that is. Float too high? bending it down closes it sooner right? Thanks for your help, Josh

Have you watched the carb while you pump the accel.? Those carbs can squirt gas out the side from the accel pump if the gasket is not right. Don,t assume the carb is right just because it,s a reman. About half of them aren,t good. I doubt if it,s flooding because you would have hard starting problems if it was. Choking it to kill it might be causing the gas leaking on the side.

Don't forget guys that if you don't have an ignition source it won't run. There might be a carburetor issue but that isn't the primary reason it's running on with the key/ignition off. Do what you will with the carburator but until you get rid of the ignition source the problem will probably continue.

slow down the idle.. check the timing for to see if its too far advanced,, dieseling will occur also with to far advanced timing just like knocking, it dont have to have an ignition source..will fire from compression, doubt it tho on an old inline.. if your worried about carbon deposits..run a little stream of water through the carb while running at fast idle..... (steam em out)....dont pour to much tho might hydro lock it.....99% of the time tho...slowin down the idle will fix it....

You can try switching to a colder spark plug too.

Try a tankfull of the highest test gas you can get, lower the idle speed and see if that cures it. One of the solenoid equipped carbs would stop the running on, but otherwise it won't be a carb problem as the carb doesn't know the ignition is off and will continue to supply fuel as long as the engine is turning over.