Michael,
In regards to "run-on" or dieseling, I was always under the impression that it was caused by a piece of carbon, or some other "hot spot" in the combustion chamber. It would be like a little spark plug you couldn't turn off. If the throttle was held partially open, as you indicate in the above post, fuel would be supplied and auto ignition would take place.
I think a fix for this would be to get the carburetor linkage adjusted so the throttle plate closes when you release the accelerator, and run some top end cleaner through the motor.
I have never figured out any relationship between excessive advance and engine run on..maybe elevated cylinder temps. This isn't one of my favorite theories.
I think the word "pinging" is a descriptor for the sound you hear when your engine detonates too early in the compression stroke...too much advance. There is technical jargon dealing with flame travel, flame front, combustion pressures etc, but I think the bottom line is that your firing the charge a little too early on the compression stroke, and it will make a audible sound...sort of like hitting sauce pan with a spoon??
I have a Motor Manual, and this is what it says for your engine: Ignition timing - distributor, Location-flywheel. A note is added that states "Engines with degree marks instead of stamped marks on flywheel have timing data noted on engine"
There must be a wealth of info for these fire engines out there...try to set it to factory specs and call it good.
Stuart
