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Jeep Cherokee Fuel Pressure Problem

Q. Mr. Ciulla, I'm glad to find this site, it looks like a lot of useful information. I have a 1998 Jeep Cherokee Straight 6, 4.0 liter. It is an automatic transmission, with A/C and multi-port fuel injection. It has 52,000 miles on it and power steering and cruise control.

Jeep Cherokee Fuel Pressure Problem

It's developed a problem starting. With the temperature changing here in Michigan I'm not sure if it's temperature related issue or not.

I purchased a fuel pressure gauge last night and connected it to the fuel rail. I found that typically it would pressurize to 45 PSI. I would then bleed it off and roll the key to the run position only. According to the schematic this both the run and start positions should energize the fuel pump relay.

I found that after repeatedly bleeding off pressure through the bleed valve on the gauge and returning the key to the run position that every other time it seemed to only pressurize to approximately 15 PSI. This seemed to a little less often the more times I did it. I probably played this game for thirty minutes or so.

I also noticed that if it only pressurized to the 15 PSI, that I could return the key to off and back to run and the second time it would continue to pressurize up to 45 PSI.

I thought that possibly the relay might be sticking. I looked in the fuse/relay box and found that the four relays all had the same part number so I switched relays between the fuel pump and the starter. We took it out to dinner last night and upon leaving the restaurant it seemed to start a little slower. Verdict is still out on that.

Is there a way to test the pressure regulator?

Is it possible for the fuel pump to not deliver the same pressure all the time? Is this indicative of a fuel pump issue? They've conveniently located the fuel filter, pump, sending unit, and pressure regulator all in or above the tank I'm not sure. If I have to drop the tank, I'm thinking that I might as well replace it all.

I saw something about an automatic shutdown relay, the article spelled out how to check a relay but didn't go into the logic about how it operates based on conditions. Could this be the issue?

Am I barking up the right tree(s)?

Thanks ahead!
Robert

Q. The problem could very well be the combination Fuel Filter/Fuel Pressure Regulator. At 52,000 miles the filter is due for replacing and since the fuel pressure regulator is part of the filter, replaing it should take care of the problem. At this point it isn't very likely the fuel pump is a problem.

You will need to drop the fuel tank to replace the combination Fuel Filter/Fuel Pressure Regulator assembly.

Additional Information provided courtesy of AllDATA

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