Just got my electric fuel pressure gauge hooked up and am wondering if my fuel pressure is okay, or if my gauge is messed up already.

Idle ~ 48 psi
Cruise @ 65mph ~ 51 psi
Full load (no vacuum) ~ 56 psi
Decel in gear (lots of vacuum) ~ 46 psi

The fuel pressure seems to vary with vacuum. For some reason I though fuel pressure was supposed to stay constant, and was supposed to be around 58 psi. Am I smoking something?

Truck is an '01 Silverado 5.3L, return system, Walbro 255, stock injectors/rail/regulator/lines/etc.

Thanks!

 

Yep. Just fine.
Your pressure changes with intake vacuum pressure changes. So you have the same balance on your fuel pressure side vs vacuum on the nozzle side inside the intake.

Mine is ~ 52 idle, 60-61 withthe vacuum line unhooked. And i think 48ish on decel/engine braking.

 

If you were to hook up a PSI vacuum/pressure on your intake you could compare and see that the fuel pressure regulator adjust the fuel pressure up 1psi for every 1psi intake manifold pressure change.


Might wanna check your fuel filter possible?

But i think 48-52 is the suggested limit for idle. And 58-62 when the vac line is dissconnected

 

I get 35psi at full throttle

 

Hey, uh..... Andy,,,,, that aint good!
My bosch 044 was dying and i saw 40psi once i got in boost over 4000rpms. Talk bout goin lean!

 

yea, the fuel injectors stopped firing and went into rep. Its fine until I reach 5200 rpm then it just plummets lol. adding a 044 inline hopefully soon so I can go wot again.

Sorry for the thread jack

 

I have the boost/vac gauge hooked up but didn't think about why the vacuum and fuel pressure would vary proportionally, makes sense. Is my fuel pressure too low then? I suppose I should get a mechanical gauge and check.

 

Went ahead and bought a Turbosmart analog gauge to mount to the rail to compare to my electric gauge.

I'm guessing the regulator is not adjustable? What could cause low fuel pressure? The filter was changed about 25k miles ago.

 

Sounds like a weak/inadequate fuel pump Andy, better get around to fixing that quick. It's bad for pistons.

Maybe that's part of why those 65#'ers weren't adequate enough?

 

Fuel pressure was 2-3 psi higher across the board today. Weird