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Broke down in the back country while hunting (HELP)

notamos

NAXJA Forum User
Location
Fort Collins, CO
99 XJ, 4.0, Auto

We've been hammering this thing this week while chasing elk. Tons of bad washboard roads going fast, climbing up rock fields, etc.

While driving this evening, it just shutoff as if i turned the key off. After 2-3 secs, it started back up by itself and kept going. A few miles down the road, same thing. Only difference was it did not restart. We came to a stop, just cranked.

I got out and pulled each of the sensor plugs on the TB and replugged them. Unplugged CPS, replugged. No change. Then, I crawled under to check the fuel pump harness (i had it unplugged recently when i bedlined my interior). It was fine. When I got back in, started immediately.

Heres the thing. Where the fuel pump wiring goes through the floor was/is being crushed by a heavy cooler. I dont have a backseat in right now nor do i have the sheet metal "shields" that were on it from the factory.

I moved the cooler before i climbed under so i could get a coat...

When the fuel pump is disconnected/shorted/etc - will it cause the xj to shutoff like a switch? Or, will it just start sputtering and die like running out of gas?

I dont trust this thing now and need to make a decision on whether my season is over or not.

No codes/CEL, vehicle has 128k and a new mopar CPS as of 6 months ago.

Thoughts?
 
I've never wired in a switch on the fuel pump to test the behavior, I would think you would feel it stumble and sputter as it ran out of fuel pressure. It could be as simple as your ignition switch is doing it, as it will kill everything, as if you turned the key. I'm guessing an easy fix, find it, and enjoy the rest of the season. You might also check your relays. My girlfriend called me one day to report "Problem. Jeep won't start." I had her change the fuel pump relay and a concerned citizen with a van full of kids helped her, and the problem was solved. I keep extra relays under the drivers seat for just this reason. Alternately I'd guess a wire is broken somewhere and makes alternate contact over bumps. Kind of like speakers & window controls do at the driver side door.
 
Thanks B! I'm up in Walden and was clear up on the Zirkel boundary!

I'll keep looking. Wish i knew for sure. If it werent dumping snow and for the fact I'm in a motel, I'd be out under it.
 
There's no float bowl like with a carb, nor an accumulator. Once you cut the power to the pump the fuel pressure drops immediately. Remember your physics, liquids are essentially non compressible.
 
The last time I had something like that it was the CPS wire bouncing around on my exhaust manifold. The last guy to put a CPS in never bothered to run the wire through the hold down ring.

Worth a look.

Now I Zip tie the CPS wire well away from danger.
 
Fuel pump will make it sputter, not cut off immediately. Might even get a few starts out of it but it won't run very well

If it started on its own then that points to a whole nother set of problems. Ignition key cylinder would explain sudden cut off and sudden restart.
 
With all the accessories turned off. When you turn the key to on, you should be able to faintly hear the fuel pump run for a few seconds.

The other thing is that you should be able to depress the Schrader valve on the fuel rail and get a healthy spirt of fuel out with the switch on.

Other than that, my guess would be cps. Don't forget to clean up the battery terminals and grounds and check all the fuses again.

I grew up south west of Walden. I used to hunt the Zirkel before it was wilderness.

Where did you hunt?

If we can determine exactly what is bad, we might be able to get you some parts up that way.
 
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Hey all. I made it back home this morning. It quit 4x coming down the canyon but restarted itself each time.

One thing to note from when it died yesterday. It would crank just fine and all power/electrical was there. Just wouldn't fire.

I'm too pissed to look at it right now. The guys I was hunting with got into the elk this afternoon and killed a few. Ugh.

NA
 
Let us know if you can duplicate it back at the house. I have a basic fuel pressure gage, and a spare CPS under the seat if it helps. May be able to drive up to FTC over the weekend to try swapping parts.
 
Hey all. Guess what?! I'm on the way home from this year's elk hunt and it happened AGAIN. Once up in Ealden last night (restarted itself while moving) and now, along 287 almost to FTC.

I noticed a sweet smell of gas when it happened, no lights, just dead engine. It isn't firing when the starter spins. I've sacked the coil out of frustration, reseated all of the sensor connectors under the hood. The fuel pump is priming fine.

This hasn't happened in a YEAR (never found the cause last time). Will the injector overheat/boil issue cause a no start?

Thoughts I can try while along the road?
 
One more thing to add. I was going about 60mph when this happened & noticed there were NO instrument cluster lights when it shutoff. Everything just went dark. Now, while trying to restart it, looks normal (lights up)
 
One more thing to add. I was going about 60mph when this happened & noticed there were NO instrument cluster lights when it shutoff. Everything just went dark. Now, while trying to restart it, looks normal (lights up)
There's a main electrical plug under the instrument cluster that jars loose and kills everything as you describe. It's common to the later models such as yours. It happens when driving over a bump such as railroad tracks.

Maybe someone will post that knows more about this particular issue...
 
are you getting spark? I had an issue similar to yours last year, had to take my daily down a jeep trail and tow it 12 miles out. after replacing crank position sensor, and still no spark, replaced the coil and it wanted to fire. Finally found that the cam position sensor was bad. snagged one from the junk yard and it fired right up. Been good a year now

Sent from my SM-G900V using Tapatalk
 
Not sure on the spark. I need to get some troubleshooting advice. I spent 5-1/2 hours sitting on the side of the road until my wife was able to get a dolly to us. It's home now, will look at it tomorrow.
 
If you aren't getting any lights either then you have a loose battery wire or main ground. Probably ought to replace the terminals at the battery, clean and reseat the hots at the alternator and PDC, and the grounds at the fender, firewall, and engine head.
 
I had something similar happen to me this evening coming home from work. It cranked and ran fine to start. Started down the highway and it just cut off for a couple of seconds like you turned the key off, then cut back on. A few seconds later it did it again, then it cut off for a third time and that was it. I coasted into a Chevron and that was that. No check engine light, not sputter, nothing. Rode shotgun in a rollback to the house. It will turn over just fine but won't hit a lick. I first thought it might be a fuel pump but maybe it's not. I won't get a chance to check it out until Saturday but wanted to see if anyone has any ideas. Before this happened it seems like the engine has to turn over more than it use to before it will start. It has a little over 183,000 miles on it and had 133,000 when I bought it so I don't know if it has ever had a pump put in it. I have replaced the coil as it developed a misfire but that was quite a while back. I also had to replace the ignition switch because I was losing power to the stereo and a few other things. I've never replaced any sensors. Any suggestions?
 
I don't know the year of your XJ, but if it really is your fuel pump, you should check the ballast resistor on the front driver's side quarter panel inside area. Remove wires from either side of it and wire them together using a jumper if they aren't long enough to connect on their own.
 
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