Guys,

I had my car on the dyno last night and it was running terribly lean. I was making more boost then last time (8.5psi vs 7.5psi) because of the cold Ohio weather.

I added lots of fuel with my UTEC, but it barely changed anything. I checked my fuel pressure, and it was right at 60psi.

I then watched my fuel pressure guage during the run. I noticed that it DROPS to 45ish PSI when the motor is under load.

The pump is a Walbro 255, the injectors are Duestchworks 650cc, and it has a return system on the car.

I checked voltage, and it is staying constant, so I'm leaning towards a bad pump. Anyone have any other ideas?

Thank you,

Kevin

 

Supercharged, or turbo? What size/trim? Which walbro pump(highpressure or low pressure)? What kind of fuel regulator??

 

The car has the APS TT kit on it. I'm not sure which walbro pump, I just know it's a 255 (and on my last dyno I wasn't running lean at all). The fuel regulator is a Mallory. We tried unhooking the boost line to the regulator, but it still did the same thing.

 

Sounds like a bad regulator honestly. With the line attached under boost the fuel pressure shouldn't move and it would be kind of odd to see a brand new Walbro not able to produce that amount of fuel flow...

 

It's not a brand new Walbro, it's been on the car for close to two years (it was installed when my Procharger was installed a LONG time ago).

Maybe I'll replace the regluator first, since it's a little easier to get to.

 

KP,

check your PMs.

 

It took a while, but I swapped out the fuel pressure regulator and the problem is fixed.