01blackout

So on my 90 xj it has a intermittent problem where the motor will quit running while cruising and won't restart. First couple times it happened we were able to jump it and start again so had battery and alternator tested battery was bad replaced the battery and today it died to day and wouldn't restart but battery was still showing good and we couldn't jump it to get it going it would just crank crank and crank and act like it wants to start put fuel pressure. Guages on it and its showing 38 psi couldn't get any spark out of it then we started pulling fuses and putin them back after we pulled the accessory fuse and put it back and then it started up and then the whole time even with the key off the radio stays on turn signals work and rear wiper turns on messed with the ignition switch and even with ignition switch unplugged. The jeep will still start went and looked at starter relay under the hood and for some reason some one ran the a wire from the ground terminal to valve cover bolt the ran the green ground wire to the ignition and left the ignition black and white wire unplugged so I put it back the way it was suppose to be green on ground black and white on ignition the jeep will start and everything but even with key off everything still has power any ideas?? Really stumped on this

67 GMC

Use punctuation and you might get some responses. We're old school here. Wecan'thelpifyouwritelikethisandexpecteveryonetokn owwhatyouaresayingandwhatisworkingandwhatisn't.

PNWjeeper

Wow that hurt my eyes to read. Try this its a write up from a member on the site, cruiser54. He will probably chime in later with some more ideas.

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

I got dizzy reading that stuff!!
Along with the ground refreshing, you should test the CPS output. Do you have access to a meter and know how to use it?

01blackout

Sorry about the punctuation I got in to big of a hurry writing it last night. I noticed that the ground that is suppose to be on the back of the head someone moved to a intake bolt. And they moved the two that are suppose to be on the dipstick. To the valve cover as well. The main ground to the battery was moved as well. its not on the bolt in front of the dipstick. They put it somewhere else on the block. Could this be my problem? And I do not have a meter to check the cps.

freegdr

With all things staying on like you say sounds like ignition switch on coloumn going out .

cruiser54

Much better. I read that and understood it with only 1/2 cup of coffee.
As for the grounds: The one from the firewall to the engine can go to the intake manifold AS LONG AS THE CONNECTIONS ARE CLEAN AND TIGHT.

As for the grounds at the dipstick stud, same thing. Move them there and make sure everything is clean and tight. The negative cable I've seen attached to the dipstick tube stud and also a little bit forward on the block. Doesn't matter as long as...you guessed it...they're clean and tight.

We wanna be sure something isn't trying to find it's ground through another component. Then we can proceed in testing other things.

Meters are $15 at Lowe's etc.

01blackout

I have two 1990's and I took ignition switch from my other one and put it on the one with issues. And same thing happened with both switches.

cruiser54

Do the grounds.

01blackout

ok ill try that and see what happens thanks!

5-90

Also, check for corrosion at the positive battery cable, at the clamp, under the jacket. I had the same problem on my 87 - turns out the B+ lead to distribution (starter motor relay screw post) was corroded enough that it would lose contact with vibration.

What really threw me was that it would happen on the road - then make contact again before the engine died, so I'd lose power and stall then start running again for no apparent reason.

Idle the engine, then go under the hood and wiggle the short lead coming off of the B+ post. If you can stall the engine doing that, you've found it.