Hey everyone. So I had low fuel pressure issues (16 PSI when running). I ran a new fuel line (straight from pump to rail without filter to test lines. cleaned fuel tank out and brand new fuel). Anyway, so now when running, it is at like 80-82 PSI. I heard this could be a return line issue, but could it be because of the lack of filter?


It was ran this way strictly as a test. It runs better, but best when I release pressure via the pressure reader at the rail.

 

Maybe the filter was just really dirty and restricted

 

Yes, the pressure regulator is in the filter. The third hose from the filter returns the overpressure to the tank. The PCM times the injector's on cycle for fuel flow at normal pressure and at higher pressure, you're getting too much fuel injected. The 02 sensor tells the PCM to cut back the mixture ratio, but it has it's limits on how much it can. I've been told the 02 sensor has to reach 600* before it sends a signal to the PCM anyway.

 

Yep! the o2 sensor has to be atleast 600*f before the pcm can rely on feedback from it. Have you gotten a new filter on ? If so how is the pressure?

 

I have not yet put a filter in. (2 New filters previous, so problem was never filter. lol)


Anyway, am still trying to find OEM fuel lines since there is something wrong somewhere in my lines. I can always just run hose and iron, but I guess every connection, like pump to filter, filter to line, and line to rail, will be hose with clamps. I would just prefer new lines, but those seem to be hard to come by...


I will be away, so weekend work will be all I can do, but I will let you know. It appears, from a few mechanics I have talked to, that the filter should restrict flow and lower the psi a little bit, but I am unsure. I guess I will see.


Can't wait to get old line out to see what the problem ended up being, though.

 

I was checking on rockauto.com and it seems you 88 XJ has a separate fuel regulator. That might be your problem.