Just the fuel pump? or something else..

I just recently picked up a 1998 XJ from a buddy. He said it ran when parked 2-3 years ago when he got his new Jeep. I bought it not running. So i get it and bring it to my work and me and a few buddies have been messin' with it. We cannot hear the fuel pump kick on when the ignition is turned on and there's zero pressure at the fuel rail. So we checked fuses and relays, and they appear to be good. We checked the connector that connects the 4 wires coming from the front of the Jeep to the fuel pump. This is what we found:
Brown wire with yellow tracer- nothing
Green wire with white tracer- grounded
Blue wire with green tracer- grounded
Black wire- powered when ignition is on, grounded when it is off.

We're not sure if this is correct as to what each wire should be doing, but with one wire not doing anything it seems a little odd. Anybody know anything about this?

Also, the fuel gauge is not reading and the voltage gauge is not reading. I don't know if this is somehow linked with the fuel pump not kicking on and the no fuel pressure or not, but any thoughts/ideas would be greatly appreciated. The Jeep is cranking over. We have searched this forum quite a few times and couldn't really find anything so I figured I'd throw a post up and hope someone can help me out. Thanks

Dark green/white should be getting positive voltage from fuel pump relay terminal D8. The relay gets its positive from fuse 22, nearby in the power distribution center.

brown with yellow is one side of the fuel gauge circuit (sensor return). It goes through a number of connectors but ends up finally at terminal A4 of the PCM. The other side, dark blue/light green, level sensor, wends its way to terminal C26.

Not sure how much this helps, but it sounds as if you're not getting voltage to the pump, so I'd start by seeing if the fuel pump relay is working.

We swapped it out with the other relays, and also tried jumping them as well. I'm going to be back at it again tomorrow so I'll double check everything again. Thanks!

you do know that a bad crank sensor can also can cut power to the asd relay which controls the fuel pump relay? just giving you another angle to work! mike

x99j said:

you do know that a bad crank sensor can also can cut power to the asd relay which controls the fuel pump relay? just giving you another angle to work! mike

Click to expand...

That's true. I'd check resistance of your crank sensor. It's something simple that should be checked as a possible cause.

I didn't know that. I'll add that to the to-do list tomorrow when I'm workin on her again. Thanks guys!

-Keep a eye on the battery, - low volts drops out the electronics fast.
-Cycle power on/off on everything a bunch - switches,relays, etc. - long setting unused, tends to gum/corrode/sticky etc. and mess up functions.
-Clean all the grounds good.
-Get a Mopar FSM, Multimeter, OBD scanner then start. (With Jeeps worth every $0.01 and don't take long to pay for themselves.)

Good Luck

When ign key is turned to 'on' the fuel pump should run about 2-3 seconds. Check to see if you read 12 Volts getting to pump during the 2-3 seconds. (Could be pump itself or power to it?)

Update: Dropped the tank, pulled the pump and found a bunch of crap inside the filter that appeared to be frozen.

sorry I beat you to the post Matty

Update:
Drained tank of crappy gas, changed fuel pump, put tank back up, added new gas, and still nothing. Also tried jumping relays with new pump in but had no effect. Any other thoughts?

Update:
Drained tank of crappy gas, changed fuel pump, put tank back up, added new gas, and still nothing. Also tried jumping relays with new pump in but had no effect. Any other thoughts?

I seem to be the only one to ever post about this so it may not apply to all models, but on my 92 limited there is security feature that kicks in any time the battery is removed. It takes away fuel pressure, not spark. Symptoms are same as bad ballast resistor, (trys to run when key is in start pos, dies when in run). I have also read that leaving the key in the ignition can activate security. To turn off this feature I have to lock and unlock the gate with the key. The dealer also told me that they used different doors different years, and to try locking and unlocking each 3 times with key. HTH Don

So have you tried putting 12 volts directly to the pump at the connector, bypassing the wiring harness? That would at least tell you that the pump is all right and that the fuel lines are passing fuel. Have you double checked grounds? At this point, it's unclear what has been tested and what has not, but I'd think the next step is to check for output voltage at the fuel pump relay, to determine whether the computer is setting it on at all, and then to check for continuity in the harness, to see if the voltage is getting where it's supposed to go.

I should also mention that on the plastic tank models such as this, you can't hear the fuel pump as readily as you do on the older ones. Have you definitively eliminated the possibility of a clogged fuel line?

Jeepnfreak's post sent me back to the owner's manual for my 99, and I notice that the "Sentry key Immobilizer" option will allow the engine to run for two seconds and then shut it off, similar to his system, if the vehicle doesn't recognize the correct transponder in the key. If this is a sentry key system, that's certainly something to look into, but the ordinary key option does not diddle with the running of the engine if it starts at all.

FYI there is no ballast resistor on this model. I assume this was replace by the ASD relay or something in the ecm

Fuel pump is brandy new

Are you getting 12 volts back at the fuel pump at all?

x2 vvvv#17 -jeepnfreak--: fuel pressure at rail?

--first 2-3 seconds of key on? same with key on steady?

I didn't get the unlock remote with mine. Every time the battery is disconnected it goes security. If there have been attempts to start the car in this condition I will get horn beeps when deactivating security, if no attempts no beeps. I know his does not have a ballast resistor, I was just pointing out that the symptoms are the same. Anything that was froozen in the tank was not fuel. If it was there it is likely to be in the fuel system elsewhere. Have you checked for fuel pressure at the rail? The easy test for this is push in on the valve core while someone else turns the key to run, it should shoot approx 5 ft.

orange said:

Are you getting 12 volts back at the fuel pump at all?

x2 vvvv#17 -jeepnfreak--: fuel pressure at rail?

--first 2-3 seconds of key on? same with key on steady?

Click to expand...

power on one of the leads, but not the other. mentioned in 1st couple posts
no pressure at rail w/ key on or being cranked over

jeepnfreak said:

I didn't get the unlock remote with mine. Every time the battery is disconnected it goes security. If there have been attempts to start the car in this condition I will get horn beeps when deactivating security, if no attempts no beeps. I know his does not have a ballast resistor, I was just pointing out that the symptoms are the same. Anything that was froozen in the tank was not fuel. If it was there it is likely to be in the fuel system elsewhere. Have you checked for fuel pressure at the rail? The easy test for this is push in on the valve core while someone else turns the key to run, it should shoot approx 5 ft.

Click to expand...

it does have power locks, but the key is just the standard key from what I can tell.




It's strange that there is movement on the amperage gauge or the fuel gauge when the key is turned to the on position, but all the lights come on like they should. Also my OBDII scanner keeps getting an error when trying to link to the ECM. going to mess with it some more later and see what else we can come up with.

Rafikie said:

power on one of the leads, but not the other. mentioned in 1st couple posts
no pressure at rail w/ key on or being cranked over



it does have power locks, but the key is just the standard key from what I can tell.




It's strange that there is movement on the amperage gauge or the fuel gauge when the key is turned to the on position, but all the lights come on like they should. Also my OBDII scanner keeps getting an error when trying to link to the ECM. going to mess with it some more later and see what else we can come up with.

Click to expand...

Sounds like you could have more than one problem. When a scanner can't connect with the PCM a shorted to ground CPS/CKP crank sensor is quite possible.

Rafikie said:

power on one of the leads, but not the other. mentioned in 1st couple posts
no pressure at rail w/ key on or being cranked over

Click to expand...

Yes, and if you'll recall from the post I made immediately after, according to my 99 wiring diagram, that means that you are not getting power to the pump. You should be getting + 12 volts at "dark green and white," which is cavity #1 on the connector. Your first job here is to trace that back, to see if your problem is in the harness or in the engine controls.

it does have power locks, but the key is just the standard key from what I can tell.

Click to expand...

Probably not the immobilizer, but if all else fails it might be a good idea to call a Jeep dealer and find out if they can determine from the VIN whether it was supposed to have one.

It's strange that there is movement on the amperage gauge or the fuel gauge when the key is turned to the on position, but all the lights come on like they should. Also my OBDII scanner keeps getting an error when trying to link to the ECM. going to mess with it some more later and see what else we can come up with.

Click to expand...

Make sure all your ground connections and connectors in the engine bay are good and clean. If this thing has sat for a while, there could be some issue there. If you haven't already, you should do a very thorough visual check of the wiring harnesses, fuses, and whatnot, including unplug and plug of every connector you can find. Look at the braided cable that connects the back of the cylinder head to the firewall, too. It often turns to dust without looking bad.