So I have used this forum for years and always found what i needed...until now.

Have a 93 xj with the 4.0 that's run fine until a few days ago. While backing out of my driveway the jeep sputtered and died. Tried starting it and all it did (and still does) is crank, but never actually starts. Sprayed some starter fluid into the throttle body and it fires up for a second, so it has spark. Next thing i realized was that i was no longer hearing the 2-3 second whining coming from the fuel pump when turning the key to start. I then checked the valve on the fuel rail with a screw driver, a little fuel spewed out and its been bone dry ever since.

Next, I tested the voltage going to the fuel pump. the three wires going to the fuel pump are green/red stripe, dark blue, and black. the blue is for the fuel gauge and tested at about 6 volts, the green/red (power to the pump) gave me 0.02 volts, (while having someone turn the ignition). I also found (on accident) that i could use the green/red wire as the ground for the blue wire..... so i MUST have a short somewhere right?

Next i did an insane amount of research on the fuel system wiring. ending up doing a bunch of fuel pump relay swapping, ballast resistor testing, ballast resistor bypass relay swapping, and ASD relay swapping. after doing all this...I ended up even more puzzled about well...everything.

so the most recent thing i decided to do was run 12v (fused with 15amp) straight to the fuel pump from the battery. and the fuel pump turned on!..kinda. I didn't get the usual whine, but if i put me ear up to the gas cap i can hear a faint whirring coming from the fuel tank. let it run to build up pressure, but no pressure at all in the fuel rail, even after letting it run for about 10 minutes.
took off the fuel filter to see if anything was coming through and some fuel DID come out of both sides of the fuel filter...

so im kind of at a stand still...this is my DD and its been down for about 3 days now

sorry for being long winded...but i wanted to give as much info as possible.
any help would be greatly appreciated!

 

You need approximately 31 psi at the schrader valve on the fuel rail for your 93 4.0 to start.

If the fuel pump is appearing to run, but you are not building pressure at the fuel rail, either one of two things is happening. The fuel filter is clogged or the fuel pump itself is toast.

 

Hey thanks for the reply! New fuel pump assembly is on the way and should be here tomorrow. the fuel filter is about a year old and it isnt clogged, but ill probably replace that too.

The main problem I am still having though is that i dont seem to be getting enough power to the pump. when i tested the fuel pump earlier, it wasnt getting any voltage. Now when i test it, it will flash 12v when the key is turned. it goes from 0v to 12v to 0v so fast that if you blink you would miss it. isnt it supposed to stay at 12v for at least a few seconds?

 

If you got your fuel pump with a lifetime warranty they will only honor the warranty with a filter purchase along with the pump purchase. If you can get your jeep on a jack stand on the passenger rear it will make life much easier. Get some ugly looking scientist safety goggles and ear plugs from harbor freight, trust me you don't want gas in your eyes or ears. plug your fuel pump assembly into the harness with the resistor unplugged (driver side fender well) to check the fuel level sender is working for the gauge before installing it. Also if you get a fuel pump that has the terminals bent across the assembly, bend them "up" like the factory has them.

https://www.cherokeeforum.com/f2/fue...2/#post2907961

That shows the problems I had with the aftermarket pump and how to fix the terminals and prevent future problems.

 

Also if your lock ring is kinda rusty, replace it! I re used my rusty lock ring and it started bending and coming apart when I tried to lock it back into place. They are $5 at advanced and come with the o ring as well.