Chris1

I have a 98 Cherokee Sport, 5spd, Driving in Spokane WA on our way home when it quit on me, just started acting like it was out of gas. Sending unit went out a while back so that was to be expected. Put gas in it, and to no avail. 2 specific things are happening, 1 Any fuel or starting fluid into the intake does increase RPM's and without that, the jeep won't stay running unless I tap the gas every so often but let it idle. will not raise RPMs. second thing, which I have never personally run into, is the intake is sucking very very hard, its really loud you can hear it with the hood down in the cab and never used to.

Another thing, is the gas cap was missing for unknown reasons, for a few months I suppose, finally got a new one and put it on there earlier that morning, about 7 hours (about 70 miles) before It started acting strange, is it possible that there might have been crap and water in the tank that , now being in a pressurized system have found their way into my fuel line? or clogged my inlet on the pump?

I haven't taken the tank off just yet, hoping to shoot everything else out of the way before I take that dive. no filter in line, not sure what's left tho haha.

RTorrez1

I would start by checking the fuel pressure on the fuel rail with a mechanical pressure gauge. The pressure should be at 49psi. Also since you said that you have been running it for a few months (not smart) make sure that you don't have water mixed in the tank.

Chris1

Its my girlfriends, i didn't realize it didnt have a gas cap till i started driving it. I put one on it, and started having problems same day. it got dark on me, going to pop a fuel line, pump some into a clear jar and have a look. if its water.. ill try droping the tank and cleaning it out. while im at it, ill have a look at the pump, and filters, ill have to walk or ride a bike across town, autozone should have a fuel pressure gauge they'll rent to me.. hope so anyways. I heard there was a way to test and find out if either the fuel pump is bad.. or another way to test the pressure gauge. the Chilton's manual my dad has , over the phone he told me what it said, it doesn't explain the steps to test them however. The pressure regulator is mounted in front of the rear axle, perpindicular to the frame,with a skid plate cover, (i think that's what that is) the book mentioned that that unit also acts as an inline filter?
idk, I am new to jeeps, and have never worked on one prior to this, total jeep newb.

Radi

This might sound stupid, but take the gas cap back off and give it a try. '96 doesn't have a return line and can pull a vacuum in the fuel tank and fight the fuel pump if the venting is screwed up. That cap might be missing for a reason, lol.
The fuel pressure regulator is part of the pump assembly, inside the tank. The cylinder ahead of the rear driver's side tire is just a filter.

Chris1

sweet, well i will change the filter and go from there. Crossing fingers its just the filter, and no gas tank removal! lol. lets see tho, Girlfriend got Tboned in the Subaru 1/2 a block from our house, cops ruled no fault, 1000's of dmg to the car we're stuck with.. lol, Jeep breaks down 30 miles from home and had to get a tow. That's been my week, lets just hope the gods are done laughing at us. lol

CCKen

The '98 XJ fuel filter is part of the fuel pump module assembly pressure regulator. There is no external filter that can be readily changed.

The fuel pump module has three filters, one on the bottom of the pump, one inside the pump housing, and one inside the fuel pressure regulator.

The Chilton and Haynes manuals suck.

Chris1

okay, well after fussing with the J bolt on the tank i finally cut it off with a hack saw, the bolt was bent right at the nut.. seized and wouldnt budge, just kept bending further, even got a "Through" wrench to get a good hold on it. In the process of cleaning up the pump, replacing the filters I can, and putting it back together momentarily to see if it fixed the problem, Its a shot in the dark, but my guess is the non vented cap caused the pump to pull crud and water into the system.

Chris1

After taking apart the fuel system, everything seems to be working.. is there anything else i could be missing? Replaced filters and everything works as its supposed to, my pump is getting good pressure and works outside the vehicle, nothing is blocking it.. So, im still not getting fuel to the rail.. well, not enough. its still acting starved for fuel, and the intake is still "screaming" loud, 4x louder than normal. Could this be a Sensor? or Fuel control module? Does something like this exist on this Jeep. (98 cherokee sport 4.0)

Chris1

it will still idle, as before, but dies as soon as you give it throttle. perplexed at the moment.

Radi

Have you attached a fuel pressure gauge at the rail?

RTorrez1

I was going to ask the same thing. But, you beat me to it. It was the first thing he should have done like I mentioned in my first post.