Help Trouble Shooting...mj Not Starting...

[gomjgo]

idk if I'm on the right track but my battery, alternator, starter and tumbler are all brand new and good to go. but my mj just won't start. won't turn over or even get my gauges turned on. nor the radio. I know I have power cuz for some reason my radio turns on with my light switch (don't ask its been like that since I bought her) but I'm thinking ignition switch...anyone have any thoughts or opinions that might help I'm open to anything. I just lifted her and now I can't enjoy her cuz she won't start!!!!

[Minuit]

If nothing happens when you turn the key to the start position, the ignition switch is the logical answer. Check for wiring problems and make sure a ground isn't messed up before you start digging though.

[ftpiercecracker1]

When you turn the key to the 'run' position does nothing happen?

 

I would see what all power you have coming into the fuse box using a test light. Something even more simple would be to check out your battery clamps and terminals, make sure they are clean clean clean.

[gomjgo]

So I took terminals off cleaned all connections still nothing. Not even the radio. My ignition switch is brand new replaced today and still nothing what so ever. BUT I did notice my battery terminal is ran to a relay that has probably 5-7 other wires on it as well...could it be the ancient relay?

 

Btw thanks for the help guys! I love my Comanche and don't wanna give up on her. this electrical is kicking my butt. Not to mention just liffting her last week. Haven't even gotten to enjoy her.

[gomjgo]

Sorry if I got carried away. But no there is nothing I disconnected my ignition switch and replaced it with a brand new one then used a flat head to move the slide to start it and nothing. Not a noise nothing. Its depressing. I feel like I'm running out of options...:/

[gogmorgo]

I might try to figure out why the radio comes on with the headlights. It might fix the problem. A bunch of years ago, my dad was trying to figure out why the brake lights on our camper weren't working, and then I noticed a plume of smoking coming out of the aftermarket tape deck. Turned out a trailer brake wire was shorting against one of the speaker wires. A couple pieces of electrical tape later, and the brake lights started working again. Tape deck never was the same again, though.

 

I'm assuming you've checked all your fuses. I'd look for what's going into the ignition switch. If there's no power there, you'll get nothing out of it. Starting there, trace "upstream" until you find where the problem is.

[gomjgo]

Sweet deal seems to be the only answer is fishing it out. Thanks again for the input! Lets hope it stops snowing so I can get to work! :)

[gomjgo]

Sweet deal seems to be the only answer is fishing it out. Thanks again for the input! Lets hope it stops snowing so I can get to work! :)

[gomjgo]

Ok so found a bad ground and my gauges work and sound from starter and fuel pump kicking on but still no magic! :/ hhmmm I'm thinking 2 month old starter? Or more bad ground?

[Minuit]

I would keep looking at grounds if I were in your position. If one is bad, it's pretty likely that others are like that also. If your Comanche is a 90 model or earlier, the grounding isn't up to the same standard as the later models and it's a big liability. I would go through my wiring with a fine toothed comb and trace the wiring from the ignition like the others said.

[cruiser54]

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.

For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely.

 

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 12-04-2012