have 01 dodge 2500 cummins.. fass 150 gph lift pump. pump wont turn on wen key cranked.. normaly runs when engine is running but itermitantly shuts off so i checked all conections etc they are all good, relay is good. im thinking ecm has internal issue. is it ok to run the fas with just ignition power instead of with ecm.. i know ecm runs it at a lower duty cycle just for cranking for some reason... just wondering if anyone has done this or ran into this, cheers

 

It will work the way you describe. Best to put a switch in though, so you can turn the pump on after the engine is started. If there is too much fuel pressure at the VP44 during cranking, it may not start.

 

i had the same issue, my ecm turned out to be bad but still lost power to lp after replacing ecm. i wired it through a toggle switch with inline fuse.

 

Not sure if this will help you, but here is a schematic:

 

Well I can't run it to a switch because I use the remote start all the time. So I wired it to ignition power, but psi is fluctuating alot! Have new filters and new fass lift pump..frustrating! And why would vp44 not fire if pump runs off acc?