Okay guys...
The vehicle: 1989 Jeep Cherokee 4.0/AW4/NP242
Problem: Will not stay running!!! When I attempt to start the vehicle, it will fire up initially. However, it will just bog down and die after the first burst of life. If I turn the key all the way over and hold it over the motor will idle like normal, however as soon as I let go of the key it will die.
The things I have attempted so far:
2 new fuel filters
new injector O-rings
set TPS properly
fuel tank is clean
Verify that pump works (by tapping it directly to the battery)
all fuel lines have been cleaned and rubber lines have been replaced.
checked crank position sensor... did not replace but heard this should not be my problem
Replaced fuel pump relay.
Now I am lost... The vehicle started and ran fine about 2 weeks ago. I then have not drove it do to rebuilding the suspension. In that time I never touched anything other then the suspension. It just decided to be a pain out of the blue!!!
Suggestions?? Dynamite?? C4??
Thanks!
Turtle
I just joined
to respond to this topic of what I'll call the "Jeep 3 second kill" because I've learned a lot from
and other Jeep forums about the problem I just experienced with our 1993 Grand Cherokee w/ 4Lthat I bought used in Nov of 2000 and more than doubled the miles on it now showing 263373 miles, and I feel like I owe it to others to share what I have learned.
Like so many responders it gave me fits after starting it up for the first time this spring and for the first time ever gave me the dreaded "3 second kill" ---- over and over and over with no fault codes except the 55 no codes. I'm a retired mechanic from the pre-computer days so when we bought our first Jeep (also used, a 1990 Cherokee Laredo that went 390,00 before rusting away) I bought the factory shop manual to get comfortable with the computer controlled ignition and multi-port injection, and also for our two later used Jeeps, 1993 and 1996 Jeep Grands, all w/ 4L and all w/ 4wd and 4speed auto.
FYI If you happen to own a 1993, like the one I mention here Jeep switched auto trannys early in 1993 from a Borg Warner to the Legacy Torque Flite 904 after designing a 4th gear addition in front of the tail shaft and published an additional volume to their shop manual for the new tranny; since called the "42RE". But they didn't revise the original manual so there a few mysteries in it, especially in the electronics.
Long story, short as possible; after reading many ideas I tested sensors and replaced questionable ones, including a complete new distributor including the cam sensor, which also operates the injectors, in spite of the code 55 because it was original and needed a cap and rotor anyway. And by then I determined that the problem was caused by the injectors losing ground from the PCM after switch from "start" to "run". Didn't the crank sensor, though some contributors suggested it, but did replace the coil because the kill problem reminded me of symptoms when the coil did once fail. I didn't ground the famous V/Y wires because I don't like short cuts unless my life somehow depends on it. (conclusion up next)
After dog-earing many pages in the shop manual back and forth to fuel and ignition pages I realized that the anti-theft included a "shutdown" function, which I had forgotten, probably because after all the years we've owned it I've never triggered it w/o being able to disarm it with lock-unlock with the ignition key or fob (simple fob in 1993, only lock-unlock). So recalling there was a trouble-shoot process in section 8W in the Jeep shop manual I rotated the key from OFF to ACC (opposite from trouble codes Off to RUN) and wow, all alarms went off including the horn and lights, which I quick disabled with the fob, and thinking "Ah Rats, the theft alarm isn't the problem so I'll call it a day and refresh my tired mind with beer and a good night's sleep."
But out of habit formed over the past many days I cranked it again before exiting, counted the seconds and sure enough it was purring like new. Though still wondering why, I backtracked my work and what I had learned and experienced;
1) As the manual said, the horn didn't sound when I tripped the alarm with the hood up to connect the battery cables, only the headlights and I quickly disabled manually with the key. But CLUE ONE, when I later closed the hood switch with a clamp and took the battery cable off on again the horn didn't sound as it should have, just the lights. I've tried all door switches and fob and they all disarmed the headlight.
2) It was only after triggering the alarm by the test procedure; the key from OFF to ACC a couple times, that the horn and headlights blasted and after that the disarm using the fob (that did previously disarm the light function as well) allowed the engine to start.
3) My assumption is that there are two separate components, or circuits, to the alarm system that must be disabled at the same time, one must activate/deactivate the lights and the other the horn before the PCM sends ground signals to the injectors.
My plan is to check the wiring in the front right door that disarms with the key but not the fob. But in the mean time the Jeep runs and starts again just fine and have put several miles on it since, and if it happens again I can simply disarm it with the test procedure OFF to ACC a couple times. As complicated as the complete ignition system is; if a reader is having this problem it may not be for the same cause, even if the injectors loose ground from the PCM, but the test procedure OFF to ACC a couple times is free and anyone can conduct it. Thanks to all who have commented on this subject and I hope my addition can help at least some before they decide "to throw their Jeep in the lake" as one writer posted.
