cheetha94607

been having a backfire on full throttle between 3500-5000rpm. check fuel pressure and found out when the car is warm it drops pressure from 35psi to 5psi at wot but returns to 30-35 when sitting at idle. please help me out here.i have a bbk 255 fuel pump,and a kirban regulator that i bought may of last year.

mjr46

I'd look for a restriction like maybe a fuel filter or a bad pump possibly, more often than not when the regulator goes bad the diaprahm ruptures and excessive pressure registers, but it could be a bad regulator.....if you have a stock one laying around swap it and try that, but more than likely it has a restricted filter or weak pump

cheetha94607

just replace the filter last week but had this problem about two weeks ago

mjr46

how old is the pump???

cheetha94607

got the pump in may 2007

mjr46

try the regulator first and if it doesn't fix it try a new pump

cheetha94607

is there any way to know if its a regulator or fuel pump

mjr46

pull the vaccum line off the regulator and drive it and see if pressure still drops, I'd lean more towards a pump or even possible a restriction in a line or even a bad connection at the pump harness connector that causes voltage drop which will limit pumps full capability but I kind of doubt that as the regulator controls pressure output and the pump is always pumping at full capability and excess returns via return line