I need help. I have a 96' GMC 6.5 turbo that rattles just like it does on diesel at cold startup. I have a 26 plate FPHE that heats the WVO to 165 degrees measured at the pollack valve. I have a seperate electric pump for the WVO. Any time I run on WVO it rattles just as it does at cold startup, Ican switch back to diesel and the rattling stops after the WVO is used up. It doesn't seem to matter what temp. the WVO is at. Other than the rattle it seems to run fine. Has anyone had this experence before?

I thought someone with more experiance might pipe up by now... but I guess not?

The only thing that comes to mind is you've got more than wvo in your wvo.. or maybe your optical sensor is miss reading the veg and dumping an improper amount into the engine?

maybe something different between our oils???

my 94 has never done what you are describing.

well I'm kind of ignorant regarding computerized vehicles.

but it sounds like the fuel quality is still too thick/cool and the engine computer is advancing the timing (like during cold start)