mtbikemarc

I've been fighting with this Jeep on and off for over a year now. Bought it for $200 (not running) gave it a tune up and new fuel pump and got a couple thousand miles out of it before it started having problems again. It is a 1995 Cherokee Sport, 2WD, Auto (bought as daily) with only 120k on it. When it runs, the engine in very strong and quick.

It would have issues where, once hot, it would begin to sputter, backfire and not react to throttle input by bogging down and quickly dying - just to restart almost right away after. This problem would seemingly be gone once it cooled down and would drive fine for a while longer.

It now will only run for a minute or two before dying. It will do this over and over, back to back.

Symptoms:

- Bogging, sputtering, backfiring (when it would actually drive)
- Starts fine but will die within a couple minutes
- Will restart directly after and continue doing so over and over
- Have never had a no start (except when I forgot to reconnect fuel pump harness after testing, haha)
- Idles high - 1100rpm constantly
- After running for a minute, will start to run rough
- No fuel pressure (gauge works) - maybe 1 or 2 psi
Seems like there is a quick spike in pressure at ignition for < one second
- Tailpipe lightly spits water while running - spits more 10secs or so before engine dies.
- Exhaust tip has heavy carbon buildup - may be normal, not sure

Parts:

IAC - Swapped w/ running Jeep (Cleaned connections and TB)
TPS - New
CPS - Haven't touched
02 - New
FPR - Swapped 2 or 3 used in and out
Plugs - New
Rotor - New
Coil - New
Wires - New
Battery - New
+ Terminal - New
Fuel Filter - New 2x
Fuel Pump - New 2x
Fuel Rail w injectors - Swapped from running Jeep
Air Filter - New
Auto Shut Down Relay - New
Fuel Pump Relay - New

Tests:

Spark - All plugs produce spark

Air - Has air - no blockage to TB - run w/ box removed to TB

Fuel - Starting from Pump: Replaced pump twice w/ filter. Blew compressed air through Out line from tank to fuel rail. Sprayed and soaked WD40 in line to help clean any blockage. At connector near fuel filter, I measured 132ohms and .5ohms on large and small ground, respectively, with the key out. 11.87V and 4.3V on large and small ground w/ key in "on" position. Swapped FPR and fuel rail (w/ injectors) from another running Jeep.
Injectors - (1) 15.0ohms, (2) 15.3ohms, (3) 14.9ohms, (4) 14.9ohms, (5) 14.9ohms, (6) 14.9ohms

Compression - Dry (1) 144, (2) 140, (3) 142, (4) 142, (5) 146, (6) 150

This is all I can think of. Please help! :-)

Gee oh Dee

Why havent you tried the crank position sensor?

I would start with that.

Huge common issue.

ZINGGG

That's what I was going to say

Gee oh Dee

I know its a rough time getting it swapped out, but its not impossible.

I would really work on replacing it. Its shouldnt be more than $35.

ZINGGG

The crank sensor? Where'd you get that hook up?!? I can't seem to find one for less than $75

Gee oh Dee

Hmm, maybe I was thinking of the coil sensor's price. But I dont remember either of them being $75. I have a commercial account with a parts store, so I get SOME help.

mtbikemarc

Trying not to spend more money on it. I'm trying to test it now but it's hard to hold a MM and spin the crank at the same time, haha.

I've avoided it until now because there is 0 fuel pressure. The CPS could have an issue but I don't see how it would affect the fuel pressure. Any thoughts?

Gee oh Dee

You hve the ballast resistor thingy?

mtbikemarc

No ballast resistor on mine. Thanks tho

ZINGGG

http://go.jeep-xj.info/HowtoCPSchange.htm

Good link to read through.
Noticed one thing that is written in that link: "when the sensor starts to fail, you get no spark or fuel so it will either not start, or suddenly without warning, stop the engine while it is running!"

Sounds like your issue, no?

mtbikemarc

Kind of but not really. I've done a CPS before on my 4x4 - when it died, it would crank and crank but never turn over. I know there are different symptoms but the Jeep will restart directly after it dies, after several attempts. So by this time the engine and sensor should be hot.

However, since I can't seem to test it myself, I'm just gonna go get one now and see what happens.

It's really odd that there is no fuel pressure. The pump primes, has voltage, etc but won't develop pressure at any point while the Jeep is running (except maybe an instantaneous spike at the moment of ignition). If the CPS were going bad and causing this problem, it would have pressure until the Jeep finally starts to die, right?