Well, I does not seem to be a "grease" issue. It runs fine on grease. To troubleshoot I actual disconnected the hose an ran them as original, it did not fix the problem. Last night replaced all hoses hopeing that it was a vacuum issue. No good.

Symptoms... starts runs on grease. On diesel after mutiple cranks it will start, at idle it will stall. If I start on grease and switch over at idle it will stall in about 5-10 seconds. ( yes, if I pump the peddle I can keep it running , but will stall when placed in gear) If I switch while driving it will run with a noticable lack of power on the highway, when slowing down it will stall.

The Greasecar set up is about 1 1/2 years old 1- 3port 1-six port.
Grease side - tank- 6port valve-primer pump-6port valve- prefilter -filter -IP
-return - 3port valve - tank
Diesel side - tank- prefilter- 6port valve-primer pump-6port valve- filter -IP
-return - 3port valve - tank
Everything about it says fuel supply ( air or lack of diesel) but....
My only other thoughts were the difference in viscosity... could it have an effect the the spray pattern if anything is dirty.

Thanks
Pat