1996 cherokee 2wd 2.5l.

Filled tank at station and car wouldn't start on the way out. hooked up fuel; pump to external battery and car + pump ran fine

Relay is working fine.

I tested the wiring going to the pump. for this I had the harness disconnected from the pump and connected to my meter. on #2 key position, I get 12v for about a second or two and 12v constant on crank. but when I connect the harness, it doesn't power the pump at all.

Goinna test the connector next. any leads on what I should check?

 

harness connected - when i backprobe there is 0v in all conditions

harness disconnected - 12v during crank and right at position 2

 

Are you certain that you're on the actual pin when you're backprobing the connector?

Here's the diagram of a 97. It should be close enough, as 96 was an odd year from what I've heard. I think this will get you there though. On the power distribution center, the fuel pump relay will have a plastic cover that can be popped off with a small flat head screwdriver. See if you can push the contact on that relay and make the pump run. That'll eliminate all the wiring from the relay to the tank/pump. It seems like the ecu might be a likely suspect in this case though. That's what provides the priming pulse when the key is initially turned on and once running.

Before you condemn the ECU, clean your grounds. I know, it sounds crazy. But it really is a common problem.

Type in a Google search:
clean grounds site:cherokeeforum.com

 

Solved it. A previous owner has spliced something on to the fuel pump positive under the seat. The wires were coming apart. Was still connected enough to get a meter read but not enough to power the pump.

real annoying. Didn't take too long to solve but I did remove the fuel pump so that's annoying

 

Awesome news! Previous owners' shade tree repairs are always the wild card in diagnostics.