Triton318

I have a 1996 XJ, 4.0 L, that will not start. It died at a stop light last week. For some reason, I thought it might be the alternator. The battery died while trying to get it started, so I knew it needed a new battery. I replaced the alternator and the battery and no luck. I had to leave for work (out of town for a week), so had it towed home.

After some research, I discovered it might be the crankshaft position sensor. I just replaced that, and it won't start.

The fuel pump turns on for about 3 seconds when I turn the key to the 2nd position, as it's supposed to. However, when I pushed the needle in on the schrader valve on the fuel rail, no fuel came out. Well, a very tiny amount sort of trickled out. But from previous experience (when relieving pressure to drop the fuel tank), I know a lot more should come out.

So I think either the fuel pump is not working properly to supply enough pressure, or the fuel filter is clogged. Being a 1996, it has an external, inline filter.

I'm thinking it would make sense to first replace the fuel filter and see what happens. If I still get no pressure at the fuel rail, would replacing the fuel pump be the next step?

Thanks in advance for your help and suggestions.

Triton318

I was reading that you're supposed to check fuel pressure with the vehicle idling. So now I'm wondering if the car has been sitting for a week and I try to start it, will that build up enough pressure to have fuel spray out of the valve (provided the fuel pump is okay)? I don't want to just assume there's not enough fuel pressure.

dave1123

If your fuel filter has 3 hoses on it, the fuel pressure regulator is inside the filter. It not, it's on top of the tank with the fuel pump. An unregulated pump should be delivering 100 psi pressure if it's in good shape. Either the pressure regulator isn't working and all the fuel is returning to tank, or the pump is not delivering.

The way this system works is the pump runs of a couple of seconds to charge the fuel rail with pressure, then shuts off. The PCM get a signal from the crank sensor that you're cranking it, then turns on the fuel pump relay and the ASD relay, which energizes the ignition and injector circuits. You were right to suspect the crank sensor because without that, it will never start. The first thing I would do after the fuel filter is backprobe the crank sensor plug to see if you're getting a pulse signal. You could also hotwire a jumper on the fuel pump relay and see if you get pressure at the rail. Maybe not in that order. I tend to think of things as I type. The fuel pump relay must be good because it runs on the pre-start part of the cycle.

When someone tells you to "back-probe" a connector, what you do is stick a needle into the back of the connector where the wires come out and use a multimeter on the needle to check for voltage. You'll have to figure out which wire or check them all. Not thru the wire insulation, but into the metal end part.

Change the fuel filter and get back to us.

Triton318

Thanks for the reply and troubleshooting tips. When you say, "You could also hotwire a jumper on the fuel pump relay and see if you get pressure at the rail." I'm assuming that will cause the pump to run continuously (while hotwired), which should result in pressure at the rail. If I do that, and there's still no pressure, are these the possible reasons: 1) a faulty pressure regulator; 2) the pump is not functioning at capacity; 3) there's a clog somewhere in the line between the tank and the fuel rail.

I'll replace the filter tomorrow morning and see what happens. And if it still doesn't start, I'll try the steps you outlined above. Thanks!

PatHenry

Fuel filter replacement is basic maintenance, so definitely change it regardless.

The pressure regulator for MOST 96's are at the rail. A few had them in the tank. Pray yours is at the rail since the fuel pump assembly for a 96 is a unique part and may be difficult to obtain.. plus the whole dropping the tank thing.

See: https://www.cherokeeforum.com/f2/the...-66136/index2/

Triton318

And I just dropped the tank, twice, three months ago for another problem. I should've changed the pump module then. Oh well.

If the pressure regulator is at the rail, where exactly is it? What should I look for? -- ***Never mind...I found out where it would be.***

Thanks.

PatHenry

Check out the linked thread I posted - there's a picture in there of both variants.

jordan96xj

96 fuel tanks have the fuel pump assembly front loaded (not on the top of the tank). So you can do them without dropping the tank. The trade-off for that convenience is that the fuel pump access hole is more prone to leak fuel if it is not properly installed/sealed.

Late model 96s have the regulator as part of the fuel pump assembly (inside the tank). Crown still makes this assembly, and finding a good price on one is not always easy. They tend to list between $150-280.

Triton318

I replaced the fuel filter. The engine started, but then died almost immediately. It did this several times. Before the new filter, it wouldn't even catch. When I sprayed starter fluid in the throttle body opening, it started and ran a little longer than without the starter fluid. So I know I'm getting air and spark. I can't check the compression, because I don't have a compression tester. I think the problem is with fuel delivery.

After it starts and dies a few times, there is gas coming out of the schrader valve on the rail. I guess I should borrow a fuel pressure gauge from an auto parts store, but doesn't the engine have to be running steadily to use a gauge and determine if there's enough fuel pressure? Could I connect a fuel pressure gauge right to the outlet hose of the fuel pump and see what the pressure is when it runs for the 3 seconds when you turn the key to position 2?

Because the engine starts and runs for a moment, does that mean the CPS is working properly? I put a new one in and I get infinite resistance when touching terminals B and C. This is the correct reading?

I'm not very good at the troubleshooting part of this. Any help or suggestions would be appreciated. Thank you.

Triton318

I bought a fuel pressure gauge and there's no pressure after cranking the engine over several times. The needle didn't move at all during engine turn over. With no fuel pressure at the rail, is it definitely the fuel pump, or could it be something else?

PatHenry

I'd disconnect the pressure regulator (assuming it's at the fuel rail) - CAREFULLY- and see if there's fuel in the line behind it. If gas comes pouring out, I'd replace the pressure regulator first.

I'd be worried that there's something blocking the line since you hear the pump kick on but have no pressure. It's certainly possible that the fuel pump just died and won't pump, but if you hear it, you usually expect at least a bit of pressure in the line. I'd eliminate the easiest stuff first and be sure that it's not pumping before pulling the assembly out of the tank.

Triton318

The pressure regulator is in the tank, with the pump module.

I just hooked up the pressure gauge to the fuel line that comes from the tank (before it goes into the filter) and got no pressure reading after having the pump turn on for 3 seconds about 4 times. Obviously there is no pressure. (And I checked the gauge to make sure it was working.)

So why would the fuel pump turn on, but not pump any fuel? Is a low voltage to the pump a possibility? Or could the pump just suddenly stop working well enough to supply pressure? Could it be the pressure regulator? I keep reading about a vacuum line, but on my Jeep, there's only one hose barb on the outside of the fuel pump module.

I'm thinking it's time to replace the pump.

PatHenry

Ugh.. yeah - since you've got no pressure right out of the tank line and it seems like the pump assembly is getting activated properly (in other words, no sign of bad wiring to the pump or something like that) then it looks like it's tank droppin' time.

The vacuum line reference that you're seeing is for the old style regulator (the one at the fuel rail) that is vacuum activated. Since SOME XJ's in the 96 model year used this style and SOME are in-tank like yours, you get confusing information from time to time. It's the joy of owning a 96 I guess.

Good luck with the parts search and keep us posted on how it goes.

PatHenry

Why the pump would turn on and not pump could be any number of things:
- tear in a line so that the pump is pumping but the fuel is coming out back into the tank
- weak pump
- bad seal or something in the pump itself such that the motor spins but it can't generate any pressure
- problems with the regulator

If you replace the whole assembly you should correct any and all of these sorts of problems. If you just replace parts of it, I'd do everything that's remotely questionable while you have it out.. hoses, regulator, pump, sender etc. etc.

Triton318

I've removed the fuel module from the tank. It's nice that you don't have to drop the tank! I've found several sources for a new module, from 175 to 209. I'm tempted to try and diagnose the issue with the module and only replace what I need to, which might be the motor and/or the regulator. However, as I have no clue as to how I would determine what's causing it not to supply pressure, I guess I'll go with the entire module.

Thanks for all the help. I probably won't be ordering it until later tonight, so if you know how I could test the module to find defective part(s), let me know! Thanks!