While traveling in KCMO and yaking on the local 146.94 in the mid '80's, an elder operator who always complained about other peoples RFI from "their" mobile complained about mine. When I told him he was incorrect, he became very indignant explaining of his years of licensed operation and his expanse knowledge of mobile operation including the fact that he, himself was mobile at that very moment with a "clean signal".

When I explained to him that I did not have any spark plugs in my diesel (mechanical pump and injectors, before the ECM style), the repeater became silent.

The moral of the story, mechanical diesels have little if no RFI. Alternator whine from time to time, which is an easy cure. Ah, the good ol' days!