Bad Walbro...how to tell?

[RS12Turbo]

Ok so I have a walbro 255 that's about 4 years old now. Yesterday I was out driving, and I got on it.....noticed it was breaking up under light load at about 11-12 psi, which is out of the norm. I looked at the af gauge, and noticed it was "off the charts" lean...17+I brought it back home and checked the static pressure. It was 40psi where I had set it a few days earlier. I tried to raise it up to 45psi, but it would only go to 41psi. I thought this was kind of odd. I checked the idle psi, and it was around 38. When I pulled off the vac hose, the pressure didn't change at all. I thought it might be my Nismo fpr, but I have a spare nismo unit, and put it on, and it did the exact same thing. Also, when I shut off the engine, the pressure drops to 0 instantly. I know a while back, it would keep pressure for 20 mins or so, before the pressure would start to bleed off. Also when I crank it, looking at the fuel pressure gauge, it builds slowly.....zero-20psi takes a few secs, then shoots up to 40 quick from there. It's hard to start too now.......gotta hold the starter for a good 15 secs before it'll fire.Is there a way to test the pump? Could it be something else besides the pump?

Thanks

[boost_boy]

Ok so I have a walbro 255 that's about 4 years old now. Yesterday I was out driving, and I got on it.....noticed it was breaking up under light load at about 11-12 psi, which is out of the norm. I looked at the af gauge, and noticed it was "off the charts" lean...17+I brought it back home and checked the static pressure. It was 40psi where I had set it a few days earlier. I tried to raise it up to 45psi, but it would only go to 41psi. I thought this was kind of odd. I checked the idle psi, and it was around 38. When I pulled off the vac hose, the pressure didn't change at all. I thought it might be my Nismo fpr, but I have a spare nismo unit, and put it on, and it did the exact same thing. Also, when I shut off the engine, the pressure drops to 0 instantly. I know a while back, it would keep pressure for 20 mins or so, before the pressure would start to bleed off. Also when I crank it, looking at the fuel pressure gauge, it builds slowly.....zero-20psi takes a few secs, then shoots up to 40 quick from there. It's hard to start too now.......gotta hold the starter for a good 15 secs before it'll fire.Is there a way to test the pump? Could it be something else besides the pump?

Thanks

Sounds like both an injector leak and a pump that's getting weak. Your pressure shouldn't just drop when you shut the engine off. Your engine should maintain rail pressure for at least 10-20 minutes after you shut the engine off. If not, you have faults in your fuel system to include your injectors, regulator, fuel line and/or the pump itself.

Dee

[RS12Turbo]

Now would the leak be an external leak or can it be internal? Because I have no visible leaks anywhere. Can pressure be lost at the gas cap, or fuel pump lid?Also , what about not being to raise the static pressure above 41psi....what would cause this?

[RS12Turbo]

Just noticed when the pump primes when i turn the key on, the gauge shoots up to 40, then when the pump gets done priming, the gauge drops right back down to 0.

Do the walbro's have a check valve? I don't remember seeing anything like that when I installed it..but again, it's been like 4 years

[boost_boy]

Just noticed when the pump primes when i turn the key on, the gauge shoots up to 40, then when the pump gets done priming, the gauge drops right back down to 0.

Do the walbro's have a check valve? I don't remember seeing anything like that when I installed it..but again, it's been like 4 years

Definitely an internal leak and from the results of the test you did, it is indicative of a serious fault in one or more components of your fuel system. Use the process of elimination. You fuel pressure gauge shouldn't be dropping down. Maybe your FP regulator has gone home again.

Dee

[RS12Turbo]

Yeah but 2 nismo fpr's doing the same thing...what are the odds? ALthough I haven't been all that impressed with the quality of them...so maybe they both are faulity.

I did recently replace my injectors....maybe I need to start with their o-rings. First though, I think I'll toss in my oe fuel pump and see if that changes anything for the better.It never ends with this car!

[RS12Turbo]

Got it sorted out....the fuel line that connects the pump itself down in the tank worked itself off somehow....hose clamp was loose. Anyway put the hose back on and tightened everything up, and she holds 38psi for a good hour before slowly bleeding off. Checked about 4 hours after, and it was at 20psi. Was able to set my static pressure too...so I think I got lucky

[boost_boy]

Got it sorted out....the fuel line that connects the pump itself down in the tank worked itself off somehow....hose clamp was loose. Anyway put the hose back on and tightened everything up, and she holds 38psi for a good hour before slowly bleeding off. Checked about 4 hours after, and it was at 20psi. Was able to set my static pressure too...so I think I got lucky

Good for you man!

Dee

[RS12Turbo]

Yeah thanks!

Also, forgot to mention.....my boost cut/ fuel cut issues I've been having forever it seems, have been cured too....seems the fuel pump issue was the culprit this whole time. Boosting 18psi all the way to redline, no cut whatsoever....and my afr's stay around 11.5 throughout with my hi-thr settings at -27 to -30

Modified by RS12Turbo at 10:34 PM 3/11/2010
Modified by RS12Turbo at 10:35 PM 3/11/2010

[float_6969]

NICE! Glad you hear you got the breakup sorted out. Any plans for coming to the National meet? I'd like to check out your car.

[RS12Turbo]

NICE! Glad you hear you got the breakup sorted out. Any plans for coming to the National meet? I'd like to check out your car.

The meet up in Nebraska? I'm considering it....although that's a pretty hefty haul from here.....I'll let you know though

[dash]

still on 370s and stock maf, or the 450s & z32 maf listed in your "chip" thread ?

[RS12Turbo]

Yes.....cleaned and blueprinted 450's by RC Engineering, and z32 maf. I guess I should update my sig