Have a 2000 cummins, just put a new vp44 and keeping the fass lift pump the old owner put on it, well at least i’d like to, but the wiring is completely ****ed, and need to figure out where i can put the relay trigger wire to send power to the fass, i hooked it up to a fuse in the dash with a fuse tap and it builds 17 psi of fuel pressure, however it loses all pressure when cranking the starter, does anyone know how i can hook the new fass pump wiring harness to the factory block mounted lift pump harness so it can be controlled by the ecm? or should i just say **** it and put it on a switch from the battery and leave the cel on the dash, i would prefer to have it as oem as possible

 

Apparently, the stock pump is powered via the engine control module... Pin 35, yellow wire with white trace. If you just want to control a relay with that circuit, run the yellow/white wire to pin 86 of the control relay, and just have pin 85 go directly to ground. Wired that way, the ECM controls the Fass Pump.

 

call, FASS should be able to get an OE wiring harness for a VP44 truck, for >100 bucks, least that's what i did some years ago buying a used FASS. I bought the spring and ball too because i didn't know the pressure, but 17psi is perfect for a VP44 so i wouldn't worry about it. If the fass harness has a weather plug at the pump, cut it off and butt splice it, plug isn't rated high enough for the current it pulls.