90 XJ completely dies then restarts right after.

Ok, I did a search and just want to make sure I've got all the candidate problems before I commit myself to fixing this thing: 1990 Renix Limited XJ. 190K miles, beat to hell, but otherwise runs great. Dedicated hunting rig with some/very little street driving.

On the trail back in Feb., it randomly died out going downhill on a very bumpy fire road. Not like sputter die out, but instantly shut down, everything went off (gauges, radio, engine, etc.). Stopped jeep, turned key off and then on again and it turned over and we continued on. Did this twice on in the weekend hunting trip with maybe 50 off road miles or so total. Weather was between 30-60* F that weekend.

1. I checked the O2 sensor wires to see if they were frayed and shorting. Looked good and not anywhere near the driveshaft/u-joints. Did not test the sensors.

2. Battery cables are nasty. I am going to replace them this weekend. Basically look like rusty cables duct taped to the battery posts. Battery is a new Optima blue top.

Given that my rig completely shut down when this happened, I'm assuming that it's not a crankshaft/camshaft position sensor or other similar. I'm also not sure if a bad ground on the main electrical from the battery would cause this as well. Other than that, the jeep starts and runs like a champ. Any ideas?

since everything shut off, you probably lost all electricity to the vehicle-- change the battery cables (not just the ends) and report back. The connection between the battery and the vehicle was probably compromised during the bouncing around.

Shorty said:

since everything shut off, you probably lost all electricity to the vehicle-- change the battery cables (not just the ends) and report back. The connection between the battery and the vehicle was probably compromised during the bouncing around.

Click to expand...

Do what Shorty says and then do the following.



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

Thanks guys. I forgot about the grounded dipstick. At least I know my dipstick will never short out. Anyways, going to tear into it this weekend and clean up/replace as needed. I think this should fix it.

Good advice. Because you're losing everything, certainly focusing on battery connections and grounds is the place to focus on. Let us know if this resolves it.

Ok, replaced the OE negative battery cable today. Got a nice new 2 guage replacement already ended with nice thick insulation. The original one, even though it was inside the plastic loom with the positive cable, was a total mess. Exposed chunks of wire about every 8 inches, plus it looked like 6 guage wire. Hosed down the block with degreaser on the dipstick nut, cleaned up the post and other wires. Put everything back and it fired right up. Going hunting with it in a couple of weeks, so if it dies on me again, I will resurrect this thread. Otherwise, I'll call this issues resolved. Positive cable was in good shape. Thanks to everyone for the recommendations.

Did you refresh the other grounds?

cruiser54 said:

Did you refresh the other grounds?

Click to expand...

I visually checked the braided grounding cable and other wiring (starter, alternator, coil, ECU, etc.). Everything, including the positive battery cable were all in fine shape, so I didn't replace them. The negative cable that I replaced was a mess. I'm surprised the jeep even started.

Planetcat said:

I visually checked the braided grounding cable and other wiring (starter, alternator, coil, ECU, etc.). Everything, including the positive battery cable were all in fine shape, so I didn't replace them. The negative cable that I replaced was a mess. I'm surprised the jeep even started.

Click to expand...

Do this to be sure everything is up to snuff.



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