low fuel pressure on 3005
Hey everybody,
This is my first post here. My fuel pressure is around 48 psi at idle. I know the unit regulates to 58 psi so I'm trying to figure out why my pressure is so low. Can a bad regulator cause this? I originally tried to use an in line pump but it also showed low pressure. I used 3 different pumps and all 3 gave me low pressure readings around 50 psi. The pumps i used were:
Fitech pump
Walbro 255 lph
Bosch 044
Currently i'm running an in tank pump using a Walbro 255 lph pump. Power is supplied via a relay. I've used 10 gauge wire for the ground and power. I have about 12.5 volts at the pump terminals. I use a 3/8 supply line and a 5/16 line for the return.
What pressure gauge are you using? Try another gauge. The typical cheap fuel pressure gauges are usually junk. Billk
How much vacuum does your engine produce? If it produces more than 18 inches, then the vacuum line that is attached to your pressure regulator on the passenger side of the throttle body is probably pulling the pressure down. Try disconnecting the vacuum line and plugging it and then read your gauge. If it goes up to 58, then you found your problem. I have this problem on my 350 SBC which produces 19 inches at an idle. I called Fitech and they said it will run fine if I leave the vacuum line connected with 48 psi, or I can disconnect the vacuum line and run it at 58. The vacuum line is primarily needed for boost applications, not normally aspirated applications. Hope this helps.
Good idea about the gauge. The one on there now is a Marshall but I don't know if they're good or bad. It was cheap though.
Jbart, I'm running around 11-12 on the vacuum. My car runs fine just cruising around but if you floor it from a roll or from a stop
the AFR jumps up into the 20s, car bogs down terrible and then slowly recovers. The engine is a 440 chrysler.
Is you pump PWM controlled? If so, the idle PWM setting may be to low, so try increasing it.
Here's an update on my fuel pressure/ high AFR readings. Jbart, I plugged the vacuum line to the regulator with no change. Then, I replaced the regulator on the fitech and the pressure remained about the same (48psi) as with the old one. For some reason I took the car out and beat on it. The car ran awesome! I floored it from a roll and from a dead stop. No AFR spikes and it just hauled ass. I have no idea why all of a sudden it's working but I'm happy. Maybe the regulator couldn't increase the fuel under heavy acceleration..... i have no idea. Thanks for the help.