So I was driving home from work today and didn't get more than 1/4 mile before I noticed that my wideband was reading way lean, almost beyond its limits. However, I have semi-open loop enabled, and as long as I was driving at a point where the PCM was commanding EQR=1.0, the STFT's were able to account for the low fuel pressure. When EQR is not 1.0 then it is in open-loop and it goes WAY lean. This was a huge issue since I have lean cruise enabled from 1200-2200 RPM at partial throttle, so it commands an EQR<1.0 and then goes lean.

I pulled over and saw that my fuel pressure at the rail was about 25psi at idle. I removed the vacuum line to the regulator and the fuel pressure didn't change. I had to run a few errands and when I got home about an hour and 25 miles later the fuel pressure at idle was about 20psi. When I turn the key off the fuel pressure instantly drops to zero.

About two months ago I noticed that my fuel system wasn't holding pressure. After engine off it would drop to zero in a matter of minutes. It used to take a long time for the pressure to drop, even after several hours it may have only dropped like 10psi.

So would this be a bad pump or a bad pressure regulator? The pump is a Walbro 255 that has about 17k miles on it installed almost 2 years ago. FPR is stock. Or perhaps the fuel line at the pump partially burst?

 

What type of hose did you use when you plumbed the walbro in there?

 

Fuel pump problem...

 

It was a submersible one from Gates, and really damn expensive, like $20 for 1.5ft.

 

Why do you say this instead of the regulator?

 

Regulators do not break often.

 

Sounds like the pump to me too. How low have you let your gas tank get lately?

 

I usually fill it up with 2-4 gallons remaining, 26 gal tank.

 

So in other words E.

 

Might be pretty dumb to mention but my filter threw me off once like this

My pumps in both my trucks with the 255 don't hold pressure- when they did it was for the first 6000 miles. My one has about 5 years the other 2 years