SG Mason

Is there any way to test/fix the fuel pump driver? or is that a new PCM problem?

SG Mason

Also would a PCM from any year after 97 from a 4.0l work if I need a PCM? I know where there is an wj 4.0l??

CCKen

If you are getting zero volts on D6 and D13, maybe you should check your CCD Bus (+) and (-) voltages. If they are pretty much matched up you may not see a .02 voltage at D6 and D13.

Refer to the DLC schematic.

Set your voltmeter to 20 VDC.

Turn key to RUN (DO NOT start the engine).

Probe DLC pin cavity 3 (+) and (-) to pin cav 4 or 5. Record the reading.

Repeat at pin cav 11. Record the reading.

If the two voltages are pretty close (same), you may not see the .02 volts at the relay, and there may be nothing wrong with the PCM FP driver.

If you see a wide margin in voltages then I would suspect the PCM, but check this first.

No stone left unturned. ;-)

SG Mason

I ordered a PCM about 20 minutes before your reply, but if it turns out that after all the testing it is not the PCM at least I will have a spare to test with and maybe help out another XJ owner in need some day.

Voltages across pin cav 3-4 and 3-5 is 2.4v. If I understand your instructions right I get the same readings from 11 cav to cav 4 and cav 5.

If I was suppose to read pin cav 3 to pin cav 11 for the second part the reading is 0v

I am getting ready to pack it in for the day, but I wouldn't be surprised if it was the PCM With the PO having jumped the fuel pump fuse the short had no place to go. End result is a lesson for me, when buying a used vehicle check all fuses for jumpers along with the other things I normally check.

SG Mason

Just picked up the replacement PCM, had to turn over the old one or pay a $65 core charge Just getting my tools together and will be heading out within the hour to install it and see if it works now. Fingers crossed because I hate having to borrow my mothers Dart. It is not a bad car, but it is not mine and it is too easy to speed with She doesn't have cruise control and I often find myself doing 70 in a 55 because it rides too smooth

I will update before the end of my day.

SG Mason

And the replacement PCM was the trick to getting it going again. Unfortunately that is two times CCKen has helped me out and it meant replacing a computer. First time it was the TCM and this time it was the PCM. Not sure what caused the TCM to go, but I know exactly what caused the PCM to go south.

Any how it works and I would just like to say thanks to CCKen once again for the diagnostics help. I still need to run it for a bit and put the OBD2 reader on it to make sure there are no other things hiding in the background. I am just happy to be driving my own vehicle again and not have to rely on other people to get around.

CCKen

Glad you fixed it (so far).

Klutch

So what exactly did cause the PCM to go south?

SG Mason

My theory is that the POs band aide repair left the PCM exposed to a surge when the fuel pump pigtail shorted.

Previous owner bridged the fuel pump fuse and never looked for the cause of blown fuses. I never knew about it till everything died last Wednesday on my way to my brothers. We figured out it was the fuel system while freezing along side the road so we just towed it to his place so I could start looking for the problem the next morning in the comfort of his garage. The next day I started looking for the problem, checked the fuse first and found the jumper. Checked the relay and the pump would turn on if I jumped that, but wouldn't turn on with a new relay. Popped another fuse so I went searching and found two wires near the fuel pump connector that the insulation had worn through. Cut out the connector because there wasn't enough wire left to make the splice at the connector. Still no start and with a little help from CCKen all that was left was the PCM. Got a PCM from the JY and it started on the 3rd or 4th crank, it just needed to build fuel pressure again. Now it starts right away no problem and is running great.