1990 Cherokee fuel pressure demon!

[bandonbound]

Like many posts I've read, I too have replaced wires, cap, rotor, filters, etc. and still have the issue. Blubbers and spits, next time runs great, next stop lite blubbers and spits again. I don't have the 30+ lbs. fuel pressure. Hangs around 25 or so. Nor does it climb 8 lbs. or so when you remove the vacuum from the regulator. Clean filter, new regulator, nothing seems to make a difference. If I just knew what makes the fuel pressure jump around 8 lbs. when you remove the vacuum I could chase that. I have a 91 that has a little different regulator but runs great and does the 8 lb. or so jump immed. when you remove the vacuum. So the pump should put our around 40 lbs. and the vacuum is a retard to around 30 lbs?? That part seems so mechanical with no electrical, relays, boxes involved. Am I looking at a fuel pump and just bite the bullet?? Thanks for any input!

[4.3LXJ]

Welcome David. The stock fuel pump will put out up to 55#. I have one that does that. The regulator is mechanical and modulated somewhat by vacuum so that an absence of vacuum will increase the pressure and output of the injectors whenever you have a heavy foot. You might try pinching off the return line where it is rubber and check the pressure. If you still cannot get over 25# out of it, better replace that pump

[bandonbound]

Thanks! Gives me some avenues to try! I'll pinch the line and check the pressure first, also, are they're any brands of pumps NOT to put in? See lots available. From $30 to 100. Just in denial about doing the tank and fuel pump assy. Thanks again for the speedy reply. Davin in Ca.

[bandonbound]

Ok. A successful fix. Sometimes on these forums you don't get what the fix was. Here's mine. Had low fuel pressure. Jeep would buck and run bad. Then run good. Did the filter, regulator, and finally the pump. That was it. Pressure rite at 31 lb, jumps to around 35 when you remove the vacuum just like it should. Only advice, take out your existing pump before. Get the brand. A Bosch or Walbro. The parts place asked whether I wanted a Bosch or Walbro. Should have asked, "what do I have, a Bosch or Walbro. I did get the Bosch replacement. A Carter kit, much bigger than Walbro, universal fit and a big headache. Wouldn't go in the hole properly, wouldn't seat and finally took out and swapped for the original Walbro replacement. Super straight forward. So don't do it on a Friday nite in the parking lot. Make sure the parts source you use has both brands. Good luck and thanks to all who helped. 4.3 LXJ especially.

[JENSSEN]

Before you change the pump bypass your balast resistor on the D/S fender and wire it direct. The balast resistor drops the voltage to the pump from 12V to 8V but when they fail they sometimes will not 100% fail they will drop the voltage lower than the 8V and then you have low pressure and a lean condition (engine will run hot). two second test but may save you replacing a pump.

-J

[bandonbound]

Thank for the ballast info. I did that before fortunately. The fuel pump was the culprit. Now, I am having those exact issues with my factory power door locks. Voltage loss. Did read a couple posts about adding relays etc. so I'm onto that. Have only around 5-6v at the actuator and understand its old wiring, factory splicing etc. Thanks again. David in Ca.

[4.3LXJ]

Where at in CA David?

[bandonbound]

I'm in So Cal. Orange Co. area. Santa Ana Costa Mesa general. In the car biz, specialize in Sube's, and seem to gravitate to lots of XJ's. Thanks for the input!

[4.3LXJ]

I am up north and have a Sube