Well, after 4 years, my rig has finally done it...

I wasn't able to drive it today, though it did get me from where I noticed the issue, back home, (about 2-3 miles) without issue. :scottm:

Specs: 1992 XJ 4.0L, AW4, 204,000 miles, np231

Here's the symptoms:

-Long crank (about 15-20 cranks)
-Responds to "poor mans prime" by firing after about 2 or 3 cranks. I had already suspected a possible disfunction of the fuel pressure regulator/pressure valve at the fuel rail prior today's new symptoms.
-No check engine light
-No codes (i checked - OBDI)
New today
-from stand-still to about 2000rpm, nothing to report
-From 2000 and up, it acts like there is power. will not accelerate. VERY consistant.
-Whilst accelerating once, it popped a bit out of the tailpipe. not a loud backfire, just pops.

Recent repairs
-Cap, rotor, plugs,wires all marked and replaced using tape and photo's. I'm 99.9%-100% sure everything went on exactly as it came off, as far as the distributor, rotor, cap and wires are concerned.

-Add to that, the fact that it has been running top notch other than the long crank, for the last 5 days since the tune-up.


My main thought is the fuel pump, which would probably explain the long crank, or possibly the fuel pressure regulator at the fuel rail, but I don't know if that would cause the "limp mode" feel that the motor has.

I changed the fuel filter with the tuneup on saturday, but it's been running fine for a week, so I doubt that it's gone clogged. (You never know, but it's not my first thought, as the truck literally will sit and idle like nothing's wrong)

OH, and I've had a TPS go out. Not the same feeling. This feels exactly like there's a governer on the engine limiting it to 2500 rpm.

Sound like possible crankshaft sensor or TPS.

http://www.naxja.org/forum/showthread.php?t=1036192

This thread describes my issue exactly, I think the next thing I'm going to do is check the fuel pressure at the rail.

The symptoms point me towards fuel delivery, not spark or engine management. I wouldn't be surprised with a leaky injector, or failing fuel pump or pressure regulator.

Don't forget--check pressure AND volume.

joe_peters said:

Don't forget--check pressure AND volume.

Click to expand...

Can you explicate that a bit more, sir? :lecture:

Cps

Does your jeep have a rear main seal leak? If yes remove cps and clean an reinstall it.I had to do this to mine because of said oil leak.It was so dirty it couldn't work.
Worth a try, it's only time.

Dying CPS, TPS, or a fuel delivery issue which may be a bad hose (leaking) on the pump in the tank.

All three can be tested, pressure gauge or volt-ohm meter tests against OEM FSM specs.

Adopt a testing based strategy here. And the first thing to test as mentioned above is fuel pressure.

Must be done with a gauge which can be rented from many parts stores; call around.

For a 92, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that vacuum line is pulling good vacuum and is not wet with fuel (which would indicate a ruptured regulator).

If the pressure is OK also do a volume test. My 2000 had good pressure but only put out 1/3 the volume it should have.

Right rear speaker..

Sounds to me like CPS, possibly fuel pump, and/or exhaust blockage. You have a 92, so you should have the 4 bolt flange just before the cat. Buy a new gasket for it (just in case) then unbolt it at the flange, it should just come off since you're socal. It'll be loud, but if it's a cat blockage, you should be able to either see it with a flashlight, or verify that it suddenly runs properly again while the exhaust is unbolted.

Since that's a $5 test (assuming the gasket tears) do it first, then I'd probably check fuel pressure while under load and if that passes, replace the CPS.

Oh, check spark? It should be a hot blue spark.

Okay, finally got a fuel pressure tester on it. It does NOT prime to any measurable psi when i flick the key on.

While running, it has 20 psi and it drops to about 18.

Yay! I'm always stoked when there's a clear, mechanical non-electronic symptom.

Makes me suspect the following things:

- bad fuel filter. Just changed it two weeks ago. Could be clogged? I might have put it on backwards or maybe the arrow is stamped in the wrong direction. (Other issues predate the filter change, but i'll still check it.)

-bad fuel hose in the tank near pump.(the crank time has been getting longer and longer)

-next on the list is a fuel pressure regulator and then finally a fuel pump.


I'll keep y'all updated.

birchlakeXJ said:

Adopt a testing based strategy here. And the first thing to test as mentioned above is fuel pressure.

Must be done with a gauge which can be rented from many parts stores; call around.

For a 92, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that vacuum line is pulling good vacuum and is not wet with fuel (which would indicate a ruptured regulator).

Click to expand...

I did this, pressure stayed at 18 psi. No fuel present that i could tell.

If you prime it a couple times, what happens? I have to prime my 98 3-4 times before it'll start due to a bad check valve. It sounds like a bad fuel filter to me though.

Check the pressure after priming a few times.

If it is your fuel pump see my "tips" from just doing one below (I believe the 92 chrysco is the same setup. Def. get the Bosch pump (cheap from Amazon/Rockauto)

A few tips...

PB Blaster the lock ring ... it came right off after PB blastering it.

Use a new lock ring

I made one BIG mistake... The 15 yr old AirTex pump had indistinguishable wire colors

I THOUGHT I had it wired up right but after getting it all back together no fuel pressure.

Realized after about a half hour of scratching my head the pump wires were reversed.

This go round, I was able to jumper the pump and use the pump to redrain the tank down and reverse the wires.

After back together the second time, started right up and the BOSCH PUMP IS SILENT....

Someone asked why I did not just reverse the wires... When I did it was arcing to ground... I think its because the 3rd wire for the sender was now providing a path fro the hot to neutral which caused sparks till I got the wires set right inside the tank.

Moral don't cross your wires and cross check if the colors are different.

kastein said:

If you prime it a couple times, what happens? I have to prime my 98 3-4 times before it'll start due to a bad check valve. It sounds like a bad fuel filter to me though.

Check the pressure after priming a few times.

Click to expand...

Yup, i did the poor mans prime. No change in fuel pressure.

SanDiegoOverland said:

Can you explicate that a bit more, sir? :lecture:

Click to expand...

Where have I been?

Ok, A good fuel pump in your 92 will deliver at least 1.05 qts. (1.0L) of fuel per minute with return line hose pinched off. If fuel pump volume is LOW inspect fuel supply system for a plugged filter or plugged fuel pump inlet filter (sock).

Ok, so I went ahead and pulled the pump, to see if I could visually detect any issues with the short rubber hose inside the tank. Sure enough this hose was BARELY installed on the male connector on the flange side of the pump assembly (as opposed to the pump side)

I was able to reattach it to the fitting, and snug the hose clamp down a surprising amount. Probably about a full turn, until tightly snug (not enough to cut the hose, just normal hose clamp tightness)

I had to stop at that point, last night, as I couldn't get the bottom of the pump to seat on the bottom of the tank, and consequently couldn't get the lock ring installed.

I'm thinking at this point, rather than struggling again to get it on, that I'll probably just drop the tank and re-install the pump/lock ring on my parking pad, where I can get "straight-down" pressure on the lock ring once I get the pump seated. I'm not in a hurry to get it done, so I might actually use the time the tank is out to attach some more substantial tie down points in the rear cargo area. We'll see.

I'm hoping that the hose being basically disconnected was the issue. I've read similar stories of that particular hose causing very similar issues in this vintage of cherokee.