Strange fuel psi issue

[jackcannibal]

Ok, here's one I've never seen before.

91 MR2 with 93 3sgte swap, Walbro 255lph pump, Supra injectors:

Running fine until all at once, instant rich problem. Checked all the basic normal causes such as leaky intercooler pipes, sensor connectors, etc. All is verified to be good. Checked fuel psi...80psi @ idle! Checked fuel psi DOWNSTREAM of the regulator (between regulator and pump)...80psi @ idle! I've never seen super high fuel psi AFTER the regulator before.

Pretty much has to be the pump, right? But what inside the pump could make this happen? Also, as soon as the car is shut off, the pump holds 0psi in the line, which tells me the check valve is crapped out for sure (if there is one on that pump-not too familiar with it).

Thanks for any info.

[Ronquest]

Hi, you said "Checked fuel psi DOWNSTREAM of the regulator (between regulator and pump)..."
After the regulator (DOWNSTREAM) should be the return to the tank. If you checked between the regulator and the pump then your checked pressure would be the same. If you realy checked after the regulator (using a "T" fitting) and your pressure was still 80 psi then you have a blocked return line. If you checked after the regulator with no "T" fitting then you would get your pumps max pressure.

A bad regulator can leak fuel pressure also when you turn off the engine.


My first guess would be the regulator but you need to verify your pressure testing hookup.

Later Ron

[jackcannibal]

Yeah, it's after the regulator. I have a really nice fuel psi testing kit, with "T" and all. I guess it's gotta be a blocked return line. I opened up the regulator (some aftermarket crap) and it was full of rust inside, for some unknown reason. I'm guessing some contaminant broke loose and blocked off the line downstream. I'll post my findings later.

[jackcannibal]

AHAHAHAHA What a douche!

Found a stupid collapsed fuel return line. Jackcannibal=idiot today.

[Ronquest]

Relatively free fix!