car is running a walbro 400 wired to the battery has stock feed line to stock fuel rail -6 return from the rail to the FPR (fuel lab mini) and stock return line from FPR to tank and is on 91 pump gas.

heres the problem. the cars fuel pressure was at 48psi thats the lowest we could get it thats with the FPR adjustment screw all the way out. the car ran fine for 500 miles (thats how many miles the pump and FPR have on them) this morning i was driving to work and the fuel pressure went from 48psi to 29psi all of a sudden.

i took the fuel hanger out to see if the pump maybe has come loose and its exactly how it was when i installed it 500 miles ago. i checked voltage and its at 14volts. i checked for leaks and theirs none. so i started to adjust the FPR to see if i could get the pressure back and the adjustment screw is now all the way down and the fuel pressure wont go above 30psi.

what do you guys think it could be? do u think the pump went bad after 500 miles? do alot of the walbro 400s go bad?

 

Sounds like the FPR to me. Any way you could check fuel pressure pre-regulator? That would give you an answer.

 

no what i was thinkin of doin tho is plugin the return line on the fpr to see if the pump makes anymore pressure

 

Not surprised at the minimum pressure of 48 psi at the rail on a rewired Walbro 400 fuel pump with no low voltage circuit. The stock return line and siphon hole are very restrictive at the kinds of flow rates that a Walbro 400 can supply. As for the 29 psi, either the FPR or the Walbro 400 took a dump. I suppose that the fuel filter could have become clogged as well, but that seems to be uncommon. Since you had the FPR full loose already, my thought is that the Walbro 400 took a dump.

 

thanks for the help guys. i took the hanger out one more time and took the pump out of it reinstalled the pump and now its workin perfect again. im guessin the rubber seal were the pump goes up in to the hanger moved a little bit and wasnt seated all the way.