208buggy

Looking for some advice. I've gone through two walbro 255 pumps in only a couple hours of runtime on my 5.3ls swap. I'm using factory 3/8" lines and I have correct voltage and a good filter. When I hook up a fuel pressure tester the fuel pressure drops as soon as fluctuate the throttle. I've also threw another regulator at it as well. Any ideas here?!

1964SS

iTrader: (1)

Gone through two pumps as in they no longer work? What type of pump? internal or external? and what regulator setup?

33willys

iTrader: (1)

As I understand it there are lots of Walbro knock-offs that will not stand the test of time. Can you tell FOR SURE that you are getting the real thing? Where are you getting them and ballpark cost? Reason I ask is that I need to buy a Walbro in tank pump.

208buggy

Thanks for the replies! I bought both pumps from "certified" walbro dealers for around 100$. The pump is an external inline pump using the factory truck style fuel rail with built in regulator. The pump is getting constant 13.7 volts.

208buggy

The pumps still work but the pressure will drop/stumble as soon as you hit the throttle.

Old Geezer

iTrader: (3)

What yr truck rails??

208buggy

2000 Silverado.

zTimbo

Are you controlling the fuel pump with the ECM?

Envy

How is the pump being powered, are you using a fuel pump relay, or are you running the pump right from the PCM? It sounds like you're getting good voltage at the pump, but I figured I'd ask. The PCM creates voltage to the pump, the pump moves gas through the lines and injectors to create pressure, as the injectors open, the pressure should drop momentarily until the regulator can add for fuel to increase the pressure back to normal. It could be that the pump is getting starved from the tank, maybe you can just setup a temp setup to eliminate a few of those things.

208buggy

The pump is controlled by the ecm by a relay. The pump is also gravity feed. I'd say the pump is about two inches below the tank.

1964SS

iTrader: (1)

Sounds exactly like my setup except I'm running the corvette regulator. Have you verified the pump has a solid ground.

208buggy

Yes, tested with a power probe.

lsxRanger94

Is the pump mounted close to the tank and below the tank? They like to push fuel, not pull.

208buggy

Yes the pump is mounted lower than the tank and about a foot away from it. Just an update I ordered a different pump that was supposed to be bigger and when it showed up it was the same pump. Right away I picked up a new regulator and put on and everything seems to work so far.

I did hook the pressure tester back on and the characteristics of the pressure seems to be a lot different than it did before. Before (with the other two pumps) the pressure would hold 58 psi when the key was on for awhile. Now with the new regulator and pump it jumps up to 58 psi and as soon as the pump is done priming the pressure falls right away. Any relevance?

208buggy

Just an update on this.... I put the buggy away for the season and now it is time to get it going again... Decided to do a cam swap and valve train upgrade.... Everything went according to plan until i went to fire it up...The motor did not want to start.. It would fire on a couple cylinders but never start. I blocked off the return line and sprayed some juice down the throttle body and it fired up. The motor would idle fine but would not rev up unless i pinched the fuel return off. After a few hours of looking things over and questioning the pump, regulator, i tested the pressure and it checked out fine to specs. From there i unplugged the MAF sensor and the motor acted NORMAL!. Motor revved up fine and ran great... Weird!