Dieseling?

Hi guys,

What causes dieseling (keeps chuggin after turned off)? Happens 8.5 times out of 10 for me.

Thanks...

lj

 

carbon buildup on valves, sparkplug, head. Stays red hot and ignites incoming fuel without spark. Timing off also.

JB

 

We used to run the old flathead Fords at a couple of thousnd RPM and slowly dump a Coke bottle of water into the carburator. The idea was the steam would clean up the carbon. Does anyone still do that? Remember those little Coke bottles? Not sure if they are still around in the US. I've seen them recently in third world countries.

 

Someone here (Mcruff maybe?) once suggested using a spray bottle w/ water to accomplish the same goal, IIRC.

 

Another possible cause that no one mentioned is the idle speed- too high can cause dieseling.

 

What does the anti-dieseling valve look like and were would it be located?

 

It's a solenoid located at the carburetor, about the size of a flashlight battery, with threads on one end so it can be adjusted in and out. Takes the place of the idle speed screw. When the key is shut off, the pin in the center of the solenoid retracts and allows the throttle butterflys to close completely.

 

Yep I use the water down the carb trick, read about it in Car craft magazine back in about 1977, works well, use restraint on how you do this. Bad gas was the norm for old muscle cars when I was in high school (no 98 octane and unleaded was becoming the norm) so water injection was a big thing, had an Edelbrock water injection unit on my old Duster

 

Thanks guys, I've got a list of things to check now. Idle is quite low (sometimes I think it's not going to keep running), but it can be hard to turn over - I'll start with the timing...

lj

 

timing too far advanced in my opinion. the water trick is best done with a spray bottle held above the carb a foot or so. spray a mist and let the vacuum suck it down. once it hits the hot valves, it will peel old gas off easily. too much and you could warp your intake valve or break a piston (water doesnt compress easily).