Question for CCKen
 

I found a post were you had explained how to test the fuel pump relay and socket a week ago. I have searched and searched and can not find it again. Is there anyway you could put a link to the post or explain again? Thank you so much for your time and help!!!

Is this what you are taking about (see pic)?


This is to test the amp draw on the pump. A 10 Amp fuse is used in place of the 15 Amp fuse. The FSM says max amp draw from the pump is 10 Amps and has you using a special test apparatus to check it. A 10 Amp fuse will tell you the same thing - if the 10 Amp fuse blows the pump has exceeded 10 Amps.


Attachment 307632


Test switch. 12 VDC, 15 Amps, on/off switch.


Attachment 307633


Pin cavities 87 and 30 are jumpered with the switch.


Attachment 307634

Is this what you needed?

I am very sorry I did not get back to you sooner. Been swamped at work and just got behind. This is helpful, but not the post I was looking for. You explained how to run a wire from a relay to the battery and then using a meter to test if the relay is working. I don't remember what pins to check. You also explained how to use a jumper and check the PDC socket. I am trying to make sure the ASD relay is working and sending power to the Fuel pump relay and then checking that relay also. I am having multiple issues with this Cherokee and trying to troubleshoot the fuel pump problem. Thank you for all the help.

It might help if I gave a little info. It is a 1998 classic, 4.0. We bought it not running for my son. The story was someone jumped the battery backwards and then the jeep sat for a long time. We changed all the fluids, fogged the cylinders, changed plug wires and spark plugs, and dropped and cleaned the fuel tank. The engine turns over, but the fuel pump never energizes. I checked the connection near the tank and am getting 5 volts constant at both pin one and three. I understand that pin one should have 12 volts for 3 seconds and then go to 0 until it receives a signal from the engine. Other problems that may also have a cause and effect are the fusible link is broken going into the front of the PDC. No gauges at all, but did the self test you posted and the gauges cycle fine. The electric fan had smoke coming from somewhere after we installed a new battery, so I just unplugged the connector. Sorry for the post being so long. And again thank you for any help.

You could try swapping the fuel pump relay with the radiator fan relay to see if the pump turns on. See PDC pic.


It could be the fusible link has melted. You can check it by disconnecting the alternator B+ cable at the alternator and at the PDC, then using and Ohmmeter, check for continuity from end to end on the cable. You should see continuity. People that hook up jumpers backwards blow the Fusible link often, and on occasion smoke the PCM.


Attachment 307574


Also, you should check fuse #11 in the JB. It powers the fuel pump relay and the ASD relay.


Attachment 307575
.

I swapped the relays and no change. Pulled fuse 11 and checked with meter and it is fine. I found a post from 2012 where you discussed checking socket 85 and 86 for the fuel pump relay and asd relay. I am getting 12 volts at 86 with key on, but 0 at 85 on both sockets. This was checked with the meter at .00 and .000. Also did the gauges check and they cycled stopping when they should.

98 fuel pump relay tests - PDC pin cavities.


Attachment 307564


98 Fuel Pump circuit:


Attachment 307565

First I want to say thank you for your patience with my ignorance with electrical problems. I have ordered a service manual to try and help myself. This is what I have found.

Socket 6-.00v, .00v.

Socket 2- 0v, 4.16v

Socket 4- 0v, 11.92v

Checked the fuse, it tested fine, but I also replaced it with a new one just to make sure. Same readings with both.