Originally Posted By: George7941
When a gas engine diesels, it is still running in the forward direction. Not relevant to the discussion here.
That's not always true. I'll never forget an old 78 Horizon (VW block engine, carbureted) that would diesel roughly forward, then occasionally kick backwards and run ridiculously smoothly, BACKWARD, blowing bluish smoke out the air intake. The only way to stop it was to go clap your hand over the tailpipe (which was indeed SUCKING air in). It was an automatic and the transmission wouldn't engage with the pump being spun backwards. I didn't believe it until it did it to me one day. I think it was dieseling on engine oil being drawn in past the exhaust valve guides.