It will diesel when the timing is off. When it not adjusted proper it will make those "hot spots". Have you ever seen an exhaust manifold glow cherry red because the timing was off? I had friends that adjusted timing by ear. All thier cars dieseled until I adjusted them with a light for them.

 

I didn't lookat ignition timing that way, but you are correct, bad timing can really get an engine cooking so that it will run with no spark.

 

Thats what I meant as well. I should have been more specific. But, you are right Pete, it is caused by timing, but because of it. (wow that makes even less sence)