mn_vette

I have a '93 LT1 running a Walbro 255hp pump with a split into the fuel rails and then into an Aeromotive adjustable FPR. At cruise and WOT the fuel pressure is exactly where it should be. However at idle around 7-800rpm the fuel pressure will be fine and then start to slowly drop. Eventually the car will go lean and stall out. If I blip the throttle when it is dropping it comes back up where it should be. Also if I program the idle to be 900rpm then it seems to be fine as well. I tried disconnecting the vaccum line to the FPR and the same thing happens. I'm out of ideas as to what it could be. Please help!

theadmiral94

have you checked the voltage from the alternator, at the battery and at the fuel pump connector?

sometimes the 200 rpm difference could make a difference in the Alternator's output, and thereby the voltage making its way to the fuel pump.

Also, could be either corrosion or too small a gauge of wire to the fuel pump -- which at lower voltage (700 rpm versus 900 rpm) might be enough to make a difference in the pump's speed and thereby its output pressure.

mn_vette

That's a very good point. I don't think that its the alternator because I just replaced it about 5k ago, but knowing my car it very well could be.

I'll check the voltages and post them back here. Any other ideas of things for me to check???

mn_vette

I put a voltmeter on the wires as I was driving down the road and the pump was dropping voltage causing the fuel pressure to drop. I ran a new power wire for it and its all fixed up now.