89 jeep cherokee

[rclayton]

My '89 Jeep Cherokee, 4.0 liter, auto, 4x4, 94,000 miles, stalls down when shifting, or especially when pulling a trailer. I've changed fuel filters twice. Also replaced the fuel pump twice, but with Auto Zone pumps. I've taken it to 3 different shops, had the fuel injectors cleaned, replaced distributor cap, rotar, plug wires, and pressure regulator. The Auto Zone pumps show 26 lbs. of pressure, and the book calls for 31 lbs. When taking the vacume hose off of the pressure regulator at idle, the pressure went to 31, I changed the regulator, but to no avail. All 3 shops were stumped as am I. They suggest replacing the Auto Zone fuel pump with a pump from a Dealer, but I don't want the expense if it's not going to help. Any suggestions?

[Cam7]

If iam right the orignal fuel pump is a Bosh. Replaced the pump on my 93 XJ and the orignal was a Bosh. If you go to the dealer you will pay twice as much. Napa has the orignal replacement. Not sure that is your problem. The pressure from the Manual on my 93 is 31 and with the regulator hose pinched 39. Try running the guage while driving and check the readings at different conditions and speeds. Also try running a jumper wire across the terminals on the resistor on the fender drivers side.Fuel pump resistor. It is to reduce the noise on the fuel pump, but it also cuts voltage.

[rclayton]

Originally Posted by rclayton

My '89 Jeep Cherokee, 4.0 liter, auto, 4x4, 94,000 miles, stalls down when shifting, or especially when pulling a trailer. I've changed fuel filters twice. Also replaced the fuel pump twice, but with Auto Zone pumps. I've taken it to 3 different shops, had the fuel injectors cleaned, replaced distributor cap, rotar, plug wires, and pressure regulator. The Auto Zone pumps show 26 lbs. of pressure, and the book calls for 31 lbs. When taking the vacume hose off of the pressure regulator at idle, the pressure went to 31, I changed the regulator, but to no avail. All 3 shops were stumped as am I. They suggest replacing the Auto Zone fuel pump with a pump from a Dealer, but I don't want the expense if it's not going to help. Any suggestions?

This problem originally started while driving in the woods. It bogged down as if the fuel filter wes stopped up. While replacing the filter, I blew out the gas into a clear jar, and it appeared to have a black, oily looking substance floating in it. Someone told me the brushes in the pump were probably bad to cause that. The replacement fuel filter helped a lot, but I,ve had this problem since. If I accelerate from a standing start, sometimes the motor pops a couple of times while bogging down. Then it usually smoothes out, but hesitates while it shifts. Sometimes it's fine if I'm not pulling a trailer. Since it stated this way, I have to assume it's a fuel problem. It would seem that someone in 3 different dealership shops, could have figured out the problem.

[Cam7]

Try the resistor if doent work might have to pull the tank off and flush it. The black crud could have damaged the pump and filter. Only way to check is to take off and see.

[89ltd]

I would also check the egr valve to see if it is opening up to soon, this would cause stumble and hesitation. Try unplugging the vacum to it and plug the line to see if it makes a difference.