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  #1  
Old November 17th, 2016, 17:06
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notamos notamos is offline
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Broke down in the back country while hunting (HELP)

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?
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  #2  
Old November 17th, 2016, 17:16
md21722 md21722 is offline
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Re: Broke down in the back country while hunting (HELP)

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.
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Old November 17th, 2016, 17:30
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Re: Broke down in the back country while hunting (HELP)

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.
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Old November 17th, 2016, 18:55
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Re: Broke down in the back country while hunting (HELP)

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.
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Old November 17th, 2016, 18:58
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Re: Broke down in the back country while hunting (HELP)

THAT'S good to know.
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  #6  
Old November 17th, 2016, 19:48
chemsolder chemsolder is offline
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Re: Broke down in the back country while hunting (HELP)

Yep and injectors are more like a precisely timed valve no pressure behind them means a drop at best gets through.
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Old November 17th, 2016, 23:47
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Re: Broke down in the back country while hunting (HELP)

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.
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Old November 18th, 2016, 07:33
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Re: Broke down in the back country while hunting (HELP)

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.
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Old November 18th, 2016, 12:05
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Re: Broke down in the back country while hunting (HELP)

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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Last edited by old_man; November 18th, 2016 at 12:13.
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  #10  
Old November 18th, 2016, 16:35
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Re: Broke down in the back country while hunting (HELP)

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
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  #11  
Old November 18th, 2016, 17:20
md21722 md21722 is offline
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Re: Broke down in the back country while hunting (HELP)

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.
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  #12  
Old November 19th, 2017, 14:10
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Exclamation Re: Broke down in the back country while hunting (HELP)

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?
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  #13  
Old November 19th, 2017, 15:04
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Re: Broke down in the back country while hunting (HELP)

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)
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Old November 19th, 2017, 21:24
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Re: Broke down in the back country while hunting (HELP)

Quote:
Originally Posted by notamos View Post
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...
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  #15  
Old November 19th, 2017, 21:24
cody4359 cody4359 is offline
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Broke down in the back country while hunting (HELP)

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

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