Anyone have a broken Walbro?

SharkRacer · May 21, 2004

Just wondering what are the odds of having a broken 255 Walbro. It seems like mine is flowing just enough fuel for cruising, but as soon as I hit boost, it doesn't want to flow anymore fuel. I'll turn my SAFC from -40% to +50% with no change in A/F mixture. It just goes extremely lean.

My pump is a little over a year old. I've heard of people receiving dead pumps, but how about a pump that doesn't flow enough?

diambo4life · May 21, 2004

I doubt that it's not flowing enough.

I have seen close to 500WHP EVO's running a Walbro 255lph pump. Have you rewired it so it can recieve 14V?:dunno: What are you using? AFPR? FMU? What rising rate? What injectors?

Brady · May 21, 2004

How do you know it is lean?

I would start by checking the fuel pressure

SharkRacer · May 21, 2004

I'm using 470's with an SX regulator. The pressure is at 40psi during idle, but I can't check it while on boost because the gauge is on the regulator. I'm using a PLX Wideband to tune it, it reads 14:1 during closed loop, but leans out severely during open loop.

eyebrowski · May 21, 2004

you are going to out flow those 470s long before you out flow the walboro pump.

diambo4life · May 21, 2004

Plugs don't lie. Have you checked them to confirm that you are running lean?

Don't you have a returnless fuel system? I could be wrong.:dunno:

Brady · May 25, 2004

diambo4life said:
Plugs don't lie. Have you checked them to confirm that you are running lean?

Don't you have a returnless fuel system? I could be wrong.:dunno:

Tuning by plugs when you have a wideband is retarted.

Try getting a vaccume pump and checking the regulator.

compuman99 · May 26, 2004

sounds to me like your FPR is messing up. Make sure the air line is good and not pluged. I had this happend to me once.

btrux06 · May 26, 2004

clamp a rubber hose to your regualtor, bring it up out of the hood on your car somehow and clamp the gauge into the hose and postion it so u can see it while driving, do this temperary just to see if your fp is holding steady under accel. yes ive done this on my car and it works great. help me find my problem of leaning out up top due to a bad filter and pump filter when i thought it was the pump that was bad, 255, but it wasnt.

diambo4life · May 26, 2004

Brady said:
Tuning by plugs when you have a wideband is retarted.

Try getting a vaccume pump and checking the regulator.

I guess everyone who has been reading plugs to check whether they were running lean or not in the past were retarded too (with or without a wideband.)

I hate name calling.

:realmad: If you are gonna make a suggestion, do not condescend someone else doing it.

I would still check the plugs.:dunno: It takes 5 minutes. If you are running that lean, you will see it. It's old school, but it works.

Taboo · May 26, 2004

Brady said:
Tuning by plugs when you have a wideband is retarted.

Physical evidence is always more reliable than output of some sensor that doesn't last for ever. Although wideband will tell the the AFR in the O2 sensor housing, spark plugs will tell what's happening directly in the combustion chambers. Another advantage of reading the plugs is that one can analyse each cylinder separately, while wideband reads AFR from exhaust gases combined from all cylinders and can't simply tell if some of them run leaner or richer than the others.

Back to SharkRacer's problem, though. Any fuel pump can go bad - and I've known of even the Walbro 255HP failures, although very uncommon (but can happen). You might want to check if the FPR raises the fuel pressure in 1:1 ratio while you apply positive pressure to its vacuum chamber using some vacuum pump such as the MityVac. While the pressure is applied, check for fuel leaks at all fuel fittings. If you're using the stock fuel filter, its replacement might possibly help as well. Another cause of the problem might be the o-ring of the pump itself - especially if the fuel pressure drops down to zero - after the pump is turned off. If you want to check the flow of the pump with increasing pressure, run some longer fuel line from the return port of the FPR to some bucket while running the pump by jumping the fuel pump check connector, then increase the fuel pressure either by applying positive pressure to the vacuum chamber of the FPR or simply using the adjustment bolt.

SharkRacer · May 27, 2004

Thanks for the ideas!!! I'm checking everything one by one. So far I've raised the fuel pressure to cover up to redline on boost. Although I shouldn't have to. The leaning seems to now only cause short hickups. It will last for only a second, then resume the normal rich tune I have set, then hickup again, then resume.....

So far I've checked the Walbro and it's screen. Seems ok. But, last night I thought about the fuel tee I still have installed from the direct port nitrous. It may be restricting the flow before the rail. I'm going to take that out and see if thats it. Otherwise, I'll keep checking other things like the fuel filter which has 40k on it.

A friend is coming into town this weekend. He also has a Walbro that I'm gonna swap with temperarily. At least I'll know it's not the pump.

btrux06 · May 27, 2004

disconnect the fuel hose coming off the top of the tank and hook a fuel pressure gauge hose up to the pump sending unit, its easy and u should get a 100 or more of pressure coming up and out, if u only build like 60 the pumps bad, thats all u have to do to check if the pumps bad or not. ive done this many times to find good and bad pumps.

Blitz E-Klipz · May 27, 2004

What do you look for when you pull the plugs? Tip being white = lean....and tip being black = rich, correct?

Anyone have a broken Walbro?

SharkRacer

diambo4life

Brady

SharkRacer

eyebrowski

diambo4life

Brady

compuman99

btrux06

diambo4life

Taboo

SharkRacer

btrux06

Blitz E-Klipz

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