Fuel Pressure Problem...

[dgoodhue]

My Fuel system consists of a 255 Walbro (I remove the stock pulsator), Stock Injectors, AFPR, and new fuel Filter.

I used to have this problem (a few months ago), when I turned up my FP over 47psi my truck would stumble, I also notice that when I used my miti vac to check my fuel pressure that at higher pressures, my Fuel pressure guage would fluctuate quite a bit, but at low FP it was rock solid (for intance 40psi would barely more and 65 psi would +/- 1 or 2 psi)


Anyways I ran a few gallons of Xlyene over a few fill ups (5 gallons total). Now my car stumble like crazy no matter what FP I am running. I look at it the other day and it at idle my FP pressure would pulse down as much as 5 psi very frequently and everyonce in a while stay sort of steady +/1 1 psi for a few seconds and then flutuate. I put a new few filter in today and it has no solved the problem. Could it be my injectors, I can feel the pulsing in my FP gauge and I don't remember that before. I listen to all my injector with an engine stethiscope and hear nothing of the unordinary in any one injector.

 

[Loeryder]

Pull the plugs and check them.
Sometimes a stumble could be a fouled plug, or one that is gapped too wide.

Plus these trucks eat plugs like sweettarts.
Also look for wires close to anything hot.

And if you are getting that reading off of an elec fuel press gauge w/ a sender, then get a mech gauge and check it at the rail.

If you have the Auto Meter short sweep 0-100PSI then there was a recall and you need to get it replaced ASAP.
Guage won't cause the stumble though. duh

Best of luck getting it smoothed out again.

 

[dgoodhue]

Pull the plugs and check them.
Sometimes a stumble could be a fouled plug, or one that is gapped too wide.

Plus these trucks eat plugs like sweettarts.
Also look for wires close to anything hot.

My plugs/wires have around 2500 miles on them (CR42TS), but I bought a set of Ur6 anyways. I am going to do the GM TEC (Top End Cleaner) one of these days when I feel like it...

And if you are getting that reading off of an elec fuel press gauge w/ a sender, then get a mech gauge and check it at the rail.

I have a mechnical gauge, I probably should try it out on another car to rule out the gauge, but I am pretty sure the flutter in the guage is real, I have never been able to feel pulsing in any fuel sytem.