Dieseling...Any tips?

[CaliWagon83]

So for the first time since I got it running again, the wagon started dieseling when I shut it down. It used to do it all the time before, but this is the first time it’s done it since I cleaned out the fuel system and had the carb rebuilt. Is it anything to worry about?

It’s doesn’t ping while driving (yet). Honestly, it’s just a minor annoyance. If it’s not causing any major damage, I’m just going to live with it until I do the engine swap.

 

[Ribbedroof]

Shut it off in drive, then shift to park

 

[CaliWagon83]

Shut it off in drive, then shift to park

Just curious...Why/how does this make a difference?

 

[565bbchevy]

Just curious...Why/how does this make a difference?

When shutting the car off in drive the load from the transmission kills the engine then you just put it in park.

 

[Wageslave]

Some of those came with an anti-dieseling solenoid that would allow the throttle blades to close farther than normal when the solenoid lost power (Key off). You could retrofit one to your carb and wire it off of the choke wire.

You can also switch your vacuum advance from manifold to ported vacuum. This should keep your ignition from advancing at idle speeds, and prevent the run-on.

Also a possibility, but less likely, is that your spark plugs might need to be one heat range colder.

Hope this helps.

 

[nawlins-tim]

As weird as it may sound, I tracked down my sbc 400 dieseling after shut off to the NON-Ethanol fuel I was using. Now the motor had a tick over 11 to1 static compression so when I used the Non-ethanol gas that was only 89 octane, maybe this was the cause. Either way you may be able to trace your problem to the fuel you use.

 

[CaliWagon83]

Sadly, out here, almost all gas is 10% ethanol, and I'm using 91 octane exclusively, which is generally the highest pump octane you can get out here.

 

[pontiacgp]

dieseling when you turn the car off could be caused by a carbon build up.

 

[oldsmobile joe]

first thing is to get a tach reading. what are your engine rams in gear and in park. too much eng speed is the general cause and the first thing i would investigate.
the most prominent are too much ignition timing and/or too much idle speed. make sure your base timing is correct and then make sure your fully warmed up idle speed is correct. info is located on your emission sticker on top of the fan shroud.
lastly, if this is a computer carb, does it have a idle speed control motor that actives the throttle? if so, find a service manual or a technician who know how to set the idle speed, they are very finicky.

 

[Ribbedroof]

dieseling when you turn the car off could be cause by a carbon build up.

Time for a balls-out WOT run!!!!