Scott_Sport99

I tried hitting everything I could with a hammer to see if I could get the truck to die(gas tank, computer, relax box, some ground wires) and nada.
If you can offer up some ideas I would appreciate it.
I drove it the day before for 1.5 hours with no problems. drove it that day for 5 minutes.
drove it yesterday for about 1 hour..no problems.
On the 2 days it was fine I never hit a bump like that one or was going 70mph if it helps you figure it out.
When It did die, it took 4 times cranking it before it restarted(makes me think fuel issue like it ran dry)but it did start back up and got me home without an issue.

crystalion

Loose wire or harness.

jeepman127

did u check ur battery terminals to see if they are loose or check to see if u got curosen around them?

CoffeeCommando

Check your ignition coil. There are 2 grounds at the bottom of it. Make sure both of those are clean and tight. Two are for the PCM (they're black with a tan tracer if you decide to take it off for inspection, and they should be connected on the right side of the coil's mount).

A ground that loses contact for even a fraction of a second to the PCM will kill everything. Same goes for a harness that is cut open and wire is exposed and swinging next to anything metallic.

But that's highly unlikely unless you use a bull bar to run small trees over that reach up into the engine bay.

Grounds are something we humans usually mess up, because they're attached to a bolt we have to removed and don't make sure it's good-and-clean or good-and-tight on to where it goes in the process of other things we're correcting. Or the bolt could have just worked itself out from engine vibration over a period of time because you/someone forgot to full tighten it amidst working on other things.

I was thinking fuel pressure, but it would sputter and then die. When something dies without any warning at all (what I like to call a clean death) it's electronic.

Also check the fuses/relays in the PDB.

CoffeeCommando

Scott_Sport99

LOL, don't worry..I didn't hit it hard, just tapping it to see if I could get the result. I am a mechanic ..not by trade anymore. Just don't know much about Jeeps.
I drove it again today for 2 hours and nada! ran fine.
thanks for the info everyone.
I will figure this out sooner or on the back of a flatbed

I looked at all the grounds and they "looked" ok. I will get a wrench on them though to be sure.
Battery cables are fine. I just put a new alt and batt in it and changed the ground cable and put super lube on it. they were clean..just the ground side was too big for the post.

PS: truck just flipped 200K

Havasu xj

i have an 89 with same issuesrunns good on asphalt not so good in dirt hit bump and shuts down anyone know if fuel pump would be affected same

cruiser54

Unless you can "see" electricity flowing, I would suggest refreshing the grounds to be sure. Do a "wiggle test" on the engine compartment harness and battery/alternator wiring. Don't use a hammer.

cruiser54

You need to do this:



Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011

cruiser54

And this:

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals making sure they haven’t retracted into the plastic holder, and then plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one. Also be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.
ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then plug them back in. I do this on every Renix Jeep I purchase or work on for someone else.
Revised 07/23/2012

CCKen

54,

He has a '99 XJ.

cruiser54

Posts #9 and #10 were intended for Hijacker Havasu XJ in Post # 7.

CCKen

Scott_Sport99,

Here's a link to one of my Photobucket albums that shows the engine bay ground points for your '99. Take a look at the pics. They're more or less for your FYI.

http://s519.photobucket.com/albums/u...Bay%20Grounds/

The Power Distribution Center (PDC) in these 97+ XJ's are kind of finicky. They don't like to be shoved around or bumped.

With the engine OFF, see if the PDC is secure; not the lid, but the whole thing. Grab it and see if it lifts up at all...gently mind you. Remove the PDC lid. Locate the Automatic Shut Down (ASD) relay - it's marked on the lid. Remove it. Examine the pins for corrosion. You'll know what to do if they are. Reinstall the ASD relay and make sure it's seated securely. Check the other relays for security while you're there. Leave lid off for now.

With the engine running, wiggle the PDC and see if anything happens, e.g., engine quits. Press down on the ASD relay and see if it reacts.

Shut engine down
.
Remove the small end cover off the PDC and examine the two cables attached there for corrosion and security. (Batt and Alt cables)

Replace PDC cover and have a beer.

Nakedginger

I had this problem a few months ago, I found that there was a bundle of wires that road up and down the oil dip stick tube and wore through the insulation. I tapped those up, and also cleaned each plug I found in the engine compartment with a spray I purchased at Napa. Something else to try is look at the wires travelling along the tranny. I have heard they can get cut over time when the tranny moves around.

cruiser54

Excellent advice.