FUEL PRESSURE HELP

[wrench22]

Ok, on my 2000 XJ i have done a fuel pressure test. With just the key on and engine off i get about 50 psi for a few moments, then it bleeds off to about 22 psi. I dont think that that is normal, but im just now learning XJ's. So i did the same test on another vehicle and the pressure didnt drop. I also did a running test on both vehicles, both held the same pressures at idle, but when i give them gas my XJ drops to about 30 psi and the other one did not. neither have the vacume opperated fuel pressure regulators, so neither one should have a drop in pressure, Right??
So, clogged filters?? Fuel pump going out?? or Pressure Regulator, which i havent found on the fuel rail or on the fuel line, so im assuming its in the tank?

 

[joe_peters]

I believe on your late model XJ the pressure regulator is integral to the fuel pump in the tank, and so is the fuel filter.

Pretty sure you are going to have to drop the tank and change the fuel pump assembly.

 

[wrench22]

K, do you happen to know anything about the pressure drops that im getting?

 

[Tim_MN]

Most questions have been asked and answered already and lots of good info is available if you use the Advanced Search. You can always just scroll to the bottom of this page and about 5 related threads are all ready for you to click on. For your first search, type in check valve.

The fuel pressure spec is 45 psi +/-5 when running and the check valve is supposed to hold a certain pressure for a specific time.

Are you having an issue or just wondering ?

 

[joe_peters]

I would suspect that the pump it's self is failing, major indicator being that when running the pressure takes a dump on you. A failing pressure regulator usually presents as too much pressure, as the pump is capable of much higher pressures than 50 psi. If the problem was the internal check valve the pressure drop off would only present when the pump is not on.

I am not acquainted personally with the late model fuel pump assembly, so maybe there is a rubber fuel line as in the early models between the top of the pump and the mounting flange, and those lines fail causing problems.

Push come to shove, even if you just have a load of crap in your fuel system, you are condemned to dropping the tank and pulling the pump assembly.

You should remove as much fuel, safely, as possible for lowering the tank.

 

[McQue]

see next post

 

[McQue]

I own an 01 XJ and have tested the fuel pressure...
1st test it dropped down to around 35 after 10 min...so I tested again....
2nd test it held above 40 for more than 25 min...so I ended the test and went to the car wash to give it a bath.