I have been playing the parts replacement game for a while now.
I am finally down to the fuel pump. During the initial prime (key to ON position) I only get 5psi. Cranking it will pump up to 40psi but bleed down to about 20psi

All that being said...would there be much of an advantage going with the 255 or even the 320 lph performance pump? I do have a performance head with larger valves...and will soon have 4 port injectors also.

 

doesn't sound like the PUMP is your issue as much as the pressure regulator is. That said I don't think the high volume, pump shouldn't hurt anything. Just remember that high volume does NOT mean higher pressure.

 

And I believe in your case the pressure regulator is part of the fuel pump. If you're into replacing the pump or regulator you might as well do the whole assembly- because it's in the tank, and it's a PITA. Also, buy a Bosch if you have the money. I've heard Carter are okay too.

 

So i went with the walboro 255 lph pump. Not as difficult as i anticipated. However i should have just replace the entire assembly. After installing the pump i still have no pressure. I disconnected the line coming out of the regulator and low and behold...no pressure. I can hear the pump running so the last part. Pressure regulator.
By the time i am done...i will have a brand new Cherokee but its been a learning experience.
Thank you all for your input.

 

Regulator wont stop pump from pumping.

 

I might have followed this logic also but the pressure regulator in a failed position closes and prevents the flow. Instead it redirects to flow back to the tank.
The fuel pump in brand new and pumping. But there is no flow out of the regulator.
Also with the symptoms i encountered it is now leading me to believe that the regulator began to fail and reduced the preasure enough to cause a lean condition in the cylinders which caused the failure of the head gasket.
Took the long way around to find this but everything...meaning everything else has been replaced.

 

In your case could be seeing its on tank instead of rail.

 

Back to working the fuel system. Installed a new pump. Pump would power up but no fuel. Installed a new pressure regulator. Now the pump won't power up. Pulled it out of the assembly and hot wired it to the battery. Nothing. So now it's time to head back to formula and buy a complete unit.

 

Not sure if this is your case or not, but I have seen several fake walbros being sold lately, just something to consider

again not saying this is happening to you, just a consideration

 

I bought an aftermarket 255lph pump. Shame on me. I am ordering the Bosch complete assembly next time.

 

I have a Walbro 255lph pump in my Firehawk.....................It has been in there doing it's thing for about 10 years now, with no issues..........

A side note: This pump will support up to around 500 horsepower........
Not necessary in an XJ...........A stock pump should provide more than enough............

 

I have a few upgrades to support. Nothing major. I should have just bought the complete assembly to begin with. I would be driving now instead of beating my head against the wall.

 

When I replaced the pump in my old XJ, the pump was not marked + or - . I had to remove it again to fix the issue. I suggest testing it BEFORE you reinstall the tank. Saves time & headaches.

I can now have a tank down in minutes.

 

The pump worked when I 1st put it in. But after I replaced the pressure regulator it stopped.