[383Sierra]

I can't get the fuel pressure to stay at 58 lbs. I have changed out the regulator twice and I bought one from Fitech and it is in there now. The pressure starts at 58 when I first change the regulator and then after driving for 15 minutes it drops to 50 and then while idling it keeps dropping to 40. I have a brand new aeromotive 340 pump . I have replaced the wiring with 10 gauge from the alternator using a relay. When blocking off the return line the pressure builds to 100lbs my gauge is right before the inlet to the throttle body. I also changed out the hose from a 6 to an 8 gauge and changed my filter to an 8 so that there are no restrictions. I also removed the filter and no change; it did not help so I put it back. It has been doing other weird things lately. It also has power fluctuating erratically.

Tech Specs

• This unit is on a 383 Chevy motor.
• Has a #8 hose from intank pump to the fuel filter at the throttle body unit.
• Has a #6 return line.

I am hoping somebody has the solution to my problem before I pull the throttle body off and send it back to FITech to diagnose any problems with the unit.

 

[Rip VW]

Just a stab in the dark but do you have a good vent on your fuel tank. No vent starves the pump after the vacuum in the tank builds...Oh another thought what about the fuel filter at the throttle body unit. Just a guess in the dark.

 

[cozwurth]

Is the pump internal to the tank, or external? Is this entire setup new? I'm just wondering if the pump itself could be getting hot and seizing up. Is there any way you can get something to measure the load on the electrical circuit as the pump is running and the pressure is dropping? You say that your power is fluctuating. Power for that circuit, or for the entire vehicle?

 

[nyceguy01]

Are you powering the pump directly through the Fitech or using a relay ?
There is a setting on the setup screen that is the Fuel pump Modulation ( Fuel PWM ) if that isnt at 100% ( means no modulation ) at idle it will slow down the pump and the pressure will go down accordingly.

 

[LATECH]

Just a stab in the dark but do you have a good vent on your fuel tank. No vent starves the pump after the vacuum in the tank builds...Oh another thought what about the fuel filter at the throttle body unit. Just a guess in the dark.

Thats where my head was taking me RIP
Also, OP needs to answer Nycegyes question about the supply voltage for the pump. That would be quite relevant

 

[35WINDOW]

My question would be how much clearance do you have between your fuel pump inlet and the bottom of the tank? I made this mistake once, and it exhibited the exact same symptoms, and after about 5 minutes or so you could hear the pump howling even through the tank-
Have you blown air through your lines to be certain you don't have a collapsing hose/line? I've had that one too-

 

[BogiesAnnex1]

Sounds like the pump, regulator, or tank vent is FUBARed.

Bogie