Engine runs on when hot

[zaa]

The engine likes to run on after being run hot. I presume the vacuum operated plunger on the left front of the carburetor is an anti-dieseling device, but it doesn't appear to work. The mechanism moves when I apply vacuum, but it doesn't seem to ever engage on its own. I haven't fully tested the vacuum valve that controls it, but I wonder, is the vacuum or electrical supplied to this system switched anywhere else on the engine? Maybe a temp switch?

[cook elandan]

sorry but not an anti-dieseling device. more than likely choke pull off.  overrunning maybe idle or timing issue. or there may be some leaky vacuum lines

[Rickf1985]

I KNOW I posted an answer to this a few days ago. Check your idle speed, if too high that can cause dieseling as can running to hot.

[MotorPro]

Several things wil contribute to run on.  Too high an rpm,too low octane , vacuum leaks and carbon build up on Pistons. Top end cleaner will usually help but be careful and follow the directions carefully. Too much too quickly can do damage.

[stopngo]

I KNOW I posted an answer to this a few days ago. Check your idle speed, if too high that can cause dieseling as can running to hot.

I will concur with that. Mine was dieseling after shut down because it was running too hot and ever since I had the Radiator repaired ......new coolant .....and all leaks stopped.................NOT ONE occurrence of dieseling thereafter. And it ran much cooler.

Check the cooling system.

[Weblamer]

I had this problem. Even replaced the entire carb trying to chase it down.

Glad I replaced the carb, THAT cleared up a lot of other issues. However it still had the run on.

Finally i just nudge the timing forward a tiny bit. I did not break out the timing light or anything, I just nudged the distributor over a little, and I am talking a fraction of an inch. Idle went down a bit, and I never had the problem again.

[Rickf1985]

You probably retarded the timing just a bit, advancing will make the idle go up unless the timing is already way too far advanced. you would also have eliminated the preignition and some heat by doing that so you killed three birds with one stone. Good shot!