ok I have be running WVO in my 96 for 2 years with out any issues untill now
the preheater was clogged with crusty flakes of WVO this then inturn screwed up my lift pump.

I filter my WVO to 1micron dewater it and is is very clean from my source to start with.

has any one had this issue and recomend a solution. I am also thinking of just making BIO instead

I run about 100 gal a month of WVO

 

My guess is the heat is too much OR the metals in the pre-heater are causing polymerization.
I would strongly suggest getting the frybrid manual for the cummins and bypassing that heater.
I run a heated pickup, heated hose-in-hose lines, heated filter and heat exchanger in the engine compartment and I find oil temps usually hover around 150F which is still less than ideal.
Try to make sure theres no copper or steel in the path of this stuff. Try to use aluminum and nylon for your plumbing and make sure to keep the two fuel systems separate.
You can run a heated filter like a racor 490R with bowl element or a dual heat setup like a vormax. Or even cook up your own solution with some coiled hose.

Id also try to save the veg for faster speeds or heavier loads so the motor is good and hot and maybe mix in a few gallons of #2 and run a good additive like power service to keep the gunk down

 

thanks
bypassing the heater was my thought also