fuel pump problems, 255 walbro Options

[TotalEclipse97]

hey guys. i installed my 255 high pressure FP about a month ago and since then she's been idleing at 800 or less. she stalled acouple times on me while i was downshifting from 3-2. once i got off the interstate (only doing about 70-75) and she died at the stop light at the end of the off ramp. any advice on what to do would be nice.

oh i've only had this problem since i installed the new FP.

[ncgalant]

Ok, here's what's happening...

Your flowing(lets say) 5lph to your engine at idle. Your pump is flowing 250lph.
Your FPR is only meant to return 120lph and can hendle 180lph or so efficiently
The extra fuel backs up in the rail and increasing your fuel pressure. Raising the idle will cause the injectors to use up some of that fuel up, but not enough to make the problem go away.

Now comes the real problem. Under boost your FPR is able to work properly because your using enough fuel. Your pressure will drop to 38lbs then raise up by whatever you boost level is. Lets say your running 15psi. Your fuel pressure is now 53psi in the rail. You let off the gas and expect to idle. Your FPR is trying to make 35psi at this point, but the above situation comes into play. Now add the fact that the pressure is already to high in the rail and now, without the injectors sucking fuel is getting higher. Your injectors open back up at 1600 rpm to catch the idle only to find way to much pressure causing a rich mess. Your car chokes out and dies.

How do you fix this. You get yourself an aftermarket FPR with a larger return line.