I am running a 1st gen motor in my Suburban. I have a vegetable oil conversion on the vehicle, and my purge times are out of sight. I use three three way valves and used to get a full purge in 45 seconds at idle. Now I am purging more than 1 minute and running for several minutes longer and still getting smokey cold starts. I don't believe my return either from the injectors or the pump or both is funcioning correctly. How much fuel per minute should I be returning and is thre a place I might be plugged or restricted. This is driving me nuts. BTW, I am running a p-pump lift pump so pressure should be high.

 

There's a filter screen and an orifice in the "banjo bolt" that connects the return to the VE. That's probably plugged up with some veggie goo.