sq_creations

I'm working on a car that has a weird problem I have not encountered yet. Im looking for some input. The car seems to run out of fuel. When driving around in town or on the freeway its fine. You can even hit a little boost and be okay. If you hit 10psi (spring pressure) above 3500rpm the wideband goes lean very linearly. It doesn't matter how much fuel I throw at it.

The orignial setup was a hondata s300, walbro 255 intank pump, aem fuel rail, aem fpr, RC 750cc injectors.

We changed out the pump for another 255 because it was 3yrs old. It didn't help.
Then I changed the aem fuel pressure regulator to a b&m regulator.

This helped a little bit. the problem moved up about 2000 rpm. so know you can hit 10psi and be okay till about 5500rpm before it goes lean. I also noticed with the engine off the fuel pressure stayed constant now where it didn't with the aem.

last night i switched out to precision 750cc's with a resistor box. I just had these flow checked so i know they are fine. It didn't change a thing.

I asked about the fuel filter and the owner said he just put it on before he brought me the car the 2 weeks ago.


Modified by sq_creations at 4:13 PM 3/13/2008

sq_creations

bump

Tried a new napa fuel filter at lunch and now it runs lean a 1000 rpm sooner. WTF!!!
could it be the stock wiring to the pump?? Thats the next thing i will try.

kyden

i'm thinking its running extremely rich, causing a rich misfire, therefore showing lean on your wideband.

sq_creations

It was the fuel rail. It was the last thing i would have expected. The car is fine now. Im thinking it may be because the aem rail didn't have a fuel dampener.