Dieseling issues

[toddbrown]

Hello, I am having an issue when I turn off the engine; it keeps trying to run or diesel I think they call it. Any ideas as to why this is happening? It doesn’t happen all the time. It’s the carbed 4.3 liter. Also, the drive train can be a little loud. I hope that is common.

 

[mdj61254]

Re: Dieseling issues

I had the same issue with the same engine when running 87 octane fuel; used 89 octane (per the owner's manual) last time out, no more dieseling...

 

[toddbrown]

Re: Dieseling issues

Excellent!<br /><br />I just took it out the other day and used 93 and no issues all day. Your right, it muist be the gas. I guess I am going to have to just pay more for better gas. <br /><br />Thansk for the reply!!

 

[youmansjason]

Re: Dieseling issues

I've got a 4.3L Volvo-Penta (carb-version) and it used to do the same thing. As long as I alternate between 89 octane and 93 octane, it runs great!

 

[bugup]

Re: Dieseling issues

Awesome info. I was having the same issue with my 4.3 LX 4 barrel this weekend. I think I'll switch to a higher octane as well. Thanks!

 

[chuck in WA]

Re: Dieseling issues

My 1985 MerCruiser 140 will do this also, which I understand to be fairly common with my engine. It only happens if I shut down soon after running at speed. If I let it cool at idle or near idle for a few minutes before shutting down, no dieseling. So, if you're cheap like me and don't want to spend extra for higher octane, try giving yourself a couple minutes cooling!

 

[toms4w]

Re: Dieseling issues

My 95 OMC 3.0L started diseling after it got a new thermostat and started running at normal temps (160-170) rather than running cold. Dealer said it could be the fuel mixture was set too rich for warmer operating temp. Higher octane gas, and adjusting the fuel mixture didn't seem to help, so I then lowered the idle and that fixed it. I hadn't paid much attention to tach at idle, and engine sounded fine, but putting the idle lower was all it took.

 

[Richard Petersen]

Re: Dieseling issues

All of you older engines. More than 200 hours. Run a can of SEA FOAM engine cleaner thru the gas tank only. Follow the ounces per gallons ratio. That way everything gets cleaned and returned to original fuel mixtures. It works on the computer jobs just as well. By removing varnish in the carb. and carbon in the engine you eliminate hard starts and Dieseling. You can can do this as often as you feel like doing it.

 

[180shabah]

Re: Dieseling issues

Ditto the seafoam, the dieseling is caused by carbon buildup in the combustion chamber. If you get rid of the carbon there is no need to waste money on the "good" gas.