In the process of tuning my car for e85 and getting lean at WOT no matter what goes into the map. Has a Walbro in it, was in the car when purchased. It was around 350hp, just now pushing the pump. I hear the stock FPR is pretty good so I was kinda ruling that out. I know the fuel filter is inside the hanger my car is 100k+, what are the chances this is the problem? Any info/input is appreciated. Thanks

 

-What is your idle fuel pressure?
-Type of turbo & max boost?
-Size of injectors, injector duty cycle% ?

 

There is a local to me Evo that is doing the same. No matter what the car wants to go lean and its got plenty of pump and injector. We were thinking it was the fuel filter as well.

 

Does it run richer with a full tank? Possibly an issue siphoning fuel from the other side of the tank when the fuel level gets to around 1/2 tank or so...

You for sure need to check out your fuel pressure at least. It could be a few different things causing this.

 

Did you use the install kit and have you checked to make sure the O-ring on the pump isnt torn in half where it goes into the pump housing?

 

I had a 255 go out on me, and one run it would be lean, the next wouldn't be, etc. If it's consistently lean then I'd venture to say it's not the pump going bad, or it would be on/off, or just off, not consistently half on, if that makes sense.

 

You need the ability to monitor fuel pressure under full boost. If you run out of pump you will see pressure drop. If it is a filter issue it will also drop.

My unmodified Walbro 255 wouldn't support more than ~425hp@wheels with 93oct.

 

I'm I the process of getting a fuel pressure gauge. Ef3 turbo only at 20psi of boost right now. FIC 1450 inj not sure of the duty cycle but I'm def not outta room. Tuner says a single Wally on e85 can get me to 500hp. Car is fine everywhere else just WOT giving me problems. Pulled the pump and checked everything and it looked fine. Car was previously tuned on 93 and was fine. Didn't think the rubber cap on top would just go bad

 

Then it must be either the pump or pump electrical wiring. I had a similar a case with a 255L, bigger turbo/injectors, the pump was a few years old. AFR got inconstantly lean at max boost, I replaced the 255L with a new DW301 & the problem got fixed.

 

Assuming there isn't any leaks or the o-ring isnt damaged or the pump itself isnt going bad , then the pump isnt keeping up with those large injectors at high rpms on E85.

U might try one of the DW pumps or the Bosch one that delivers more fuel.

Lastly do a rewire for the pump to deliver better voltage to it that will also help as well.

 

Which pump do you have...255 or 400?

 

Car starts going lean at 4500 rpm, 255 GSS342

 

Could a boost leak be part of the problem?

 

A boost leak would make it rich. Your best bet it to rig up a gauge to the fuel line somehow that you can monitor it while driving. As manifold pressure goes up, so should fuel pressure. If it starts to drop even a few psi at higher rpm while boost pressure holds, replace the pick-up screen and the inline filter. If that don't fix it, replace the pump.

 

Inline filter?