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68gmsee · 05-08-2008, 12:11 AM

10/4 on dieseling referring to running after ignition is turned off. Either backwards or forward. Basically it means that there's no ignition spark (like in a diesel engine) but the engine keeps running. The piston moving down sucks in more fuel from the carburetor.

As mentioned by Longhorn Man and ed2552, several things can cause this. The most common is a hot spot on the piston due to carbon buildup that can be caused by bad gas. Also timing, leaking carb and overheating are other causes of dieseling.

The hot spot ignites the fuel after you shut the ignition off and the explosion causes the engine to keep turning. It may also turn backwards depending on where the piston is when the fuel explodes.

The first thing I did on my truck was replace the spark plugs and checked timing. Then I ran the gas tank down as low as I could get it, poured in two cans of STP gas treatment and filled the tank up to the top. I did that on two tanks full before it stopped. If it's real bad, you may have to do that for a while and run the truck to burn off the carbon.

05-08-2008, 12:11 AM	#6
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Dieseling help for a noob... 10/4 on dieseling referring to running after ignition is turned off. Either backwards or forward. Basically it means that there's no ignition spark (like in a diesel engine) but the engine keeps running. The piston moving down sucks in more fuel from the carburetor. As mentioned by Longhorn Man and ed2552, several things can cause this. The most common is a hot spot on the piston due to carbon buildup that can be caused by bad gas. Also timing, leaking carb and overheating are other causes of dieseling. The hot spot ignites the fuel after you shut the ignition off and the explosion causes the engine to keep turning. It may also turn backwards depending on where the piston is when the fuel explodes. The first thing I did on my truck was replace the spark plugs and checked timing. Then I ran the gas tank down as low as I could get it, poured in two cans of STP gas treatment and filled the tank up to the top. I did that on two tanks full before it stopped. If it's real bad, you may have to do that for a while and run the truck to burn off the carbon.