GregM

iTrader: (1)

I'm having some issues with fuel pressure. I have a single in tank Walbro 255lph pump and a Sard FPR. I can not reduce fuel pressure below about 43psi, which is fine as thats where I'd like it, but whats happening now is the fuel pressure will sometimes sit at 48psi, and when that happens, I can not adjust the pressure below that. The pressure seems to change between about 43psi and 48psi, and could be anywhere in between each time I start the car after its sat for awhile.

I have changed to a Tomei FPR and only had it in the car for a few minutes, but could not adjust that below 48psi. This makes it very hard to tune the car as AFR's can be quite different between runs due to the different pressures. The pressure generally doesn't change from what it is when started until the car sits for awhile.

Does anyone have any idea why the fuel pressure would behave the way it is?

GregM

iTrader: (1)

no one?

03whitegsr

iTrader: (8)

Do you have the fuel pressure solenoid connected still? If so, disconnect it from the line and go straight to the intake manifold and see if it changes the behavior.

Or possibly something internally on the regulator is wrong. I had an Aeromotive where the vacuum fitting was rubbing on the spring and it caused similar "funky" fuel pressure variances. Ground down the fitting so it didn't rub and it fixed the problem.

GregM

iTrader: (1)

Its still through the solenoid, but this is also with the vacuum line off trying to set the base pressure. I'll bypass the solenoid anyway as I want to get rid of all that crap.

I'm going to change FPR's again, if its still happening, I may try the factory FPR, but have no way telling what the fuel pressure is with it installed.

GregM

iTrader: (1)

I've just checked the voltage at the pump and its 12.54volts at idle. I had read that the voltage to the pump is lower at idle and increases as load increases. Doing a search, so far I can't find any threads which say what is normal at idle. Can anyone give me a figure?

GregM

iTrader: (1)

Found a thread finally, sounds like the voltage should only be about 8 volts at idle, sounds like that could be the cause of my issue, now to figure out why.

mirkendargen

iTrader: (2)

Is the pump wired straight to the battery? A lot of people do that.

GregM

iTrader: (1)

No, factory wiring.