snagster123

Hey guys.. I found this old thread and it is very close to what I have going on ( https://www.cherokeeforum.com/f2/98-...l-pump-233576/ )... No fuel pressure, no power at the fuel pump wire harness connection. I have dropped the tank so I can check the fuel pump, and it also needs a new fuel vapor tube (the old one looked like rusted swill cheese!). With key on, there is power at the fuel pump relay, and Fuse# F21. I have not checked the junction box fuses 11 and 20 yet. If they check out good, any other ideas?

**Also, what is the part of the fuel system (driver's side in front of but near the rear wheel) that the fuel vapor tube and fuel lines go into? It is under a metal box/cover about the size of a tissue box. The bolts are totally rusted and I am afraid to try and get into it if it's not broken.

snagster123

Update: I rigged up a test light to the quick disconnect 12v positive and ground. What is happening is at the moment you turn on the ignition key there is power to the circuit for about 1.5 seconds and then it cuts off. I'm guessing the PCM is shutting it down???

Any thoughts?

Thanks,
Andy

UKXJ

My first suspect would be the relay - just swap it with the one for the fan. If it makes no difference, move on, if it cures the problem, it's a quick, cheap easy fix, 'cos any old Bosch style relay will do.

snagster123

already tried that... no change.

snagster123

I am trying to find out exactly how to test this CPS at the harness... do you do it with the harness unplugged or plugged in. if plugged in, how did you tap into the wire to get the reading?

I just tested it with harness unplugged and got zero readings on either side with the ignition on, and also cranking. No voltage.

97grand4.0

Any chance your wiring behind the driver side rear panel is corrupted with corrosion on the harness connections? This is to the immediate left when you open the rear hatch. Has the wiring for pump and rear lights.

snagster123

This Jeep has the wire harness going through the floor under the rear seat on the drivers side. It appears to be fine.

Dave51

I hope your fuel lines don't go into it!

It's vapor sucker-upper send to the intake make your CEL send P0455 codes-- thing.

If the plate falls off you can fab something up:

Dave51

3 seconds, but close enough.

Dave51

On either side of what? The CPS or the harness?

snagster123

Both. the male and female side. On either side of the wire harness plug. On the CPS side (unplugged) there is no voltage from any of the pins (I know the center pin is ground). And on the plug side to the PCM there is no voltage from the Orange wire (which should be 5v).

Also, the pins are not damaged and appear to be making good contact at the connector.

Dave51

Well that's not very good.

See if there's power coming out of the PCM C1 A17. Or if camshaft position sensor has power.

Dave51

Or the throttle position sensor....

snagster123

How do I check this C1 A17? And for the camshaft pos sensor... is this checked at the quick disconnect?

Thanks,
Andy

Dave51

MAP sensor...