As this is my first post I'd like to say hi to all you folks and happy holidays as well.
I have a fuel pressure question, Was heading to town yesterday when i noticed i had no fuel pressure....Crap..(have a mechanical fp gauge plummed to fuel filter) I turned around and went back home, I have a Walbro 392 with pre filter mounted on the frame just ahead of the tank, took all the line loose and blew them out thinking there may be crap in them, drained fuel filter/replaced, never realy found anything in the lines i figuered was a problem. Anyway i have fuel pressure but not rock solid. Is it possable that the "pop off" valve got stuck on the vp44? As i never really found a cause of my loss of fp it makes me nervous.

 

My walbro would fluctuate all over the place and sometimes would go to 0 but come back in a second or two. Replaced the pump with another and the problem went away. If you have a bypass you may take it off and check for debri or if it is hanging up.

 

Well...Ordered a new pump, fuel pressure has settled back to normal, now i am wondering if i got some water in the fuel and had some ice in the lines.
Bruce

 

If it was ice the truck would have stalled, I'd suspect the LP is going out, as the VP is sucking the fuel without the aid of the LP, if the "pop off valve" was stuck open or closed I doubt it would change your pressure much as it is a very tiny restriction (others might chime in to confirm/deny) it would not make the FP go to zero thats for sure. only info I can find in the factory service manual about the pressure relief is that if its faulty it will/can cause hard starting, (I belive if its weak/faulty it allows the IP to drain fuel back to the fuel tank)