quitthaten

I have a 1990 Jeep Cherokee with a voltage problem. Weither Im driving in the day or at night with the lights on. My less than a year old battery's power is being drained. I have a less than a yr old starter and alternator on the jeep. While Im driving I can see the volts decreasing, when I put on the lights the volts decrease. I took it 2 the shop they said the starter, battery, and alternator where all good. They believe it is an electrical problem. I think tht it maybe the ingition coil because I put a used one in before I replaced the battery, alternator and starter. And thts when I noticed volts going up and down. So, I think tht maybe it...What do u think? Oh also, my truck is idelied up high

HELP ME IM SUPER FRUSTATED!!!!!

tjwalker

An ignition coil would not cause a fluctuation in voltage. Also, the starter is not in play.

Here are the top two things that come to mind.

1. Grounds. Be sure you have FRESHENED them! Renix vehicles are very sensitive to marginal ground issues. More on that below. DO IT.

2. Testing of the alternator can and often is not accurate. I have seen many alternators that test good be faulty. Many of the bench testers at parts stores only test for voltage and not for current, which does the work. People that rebuild alternators have the proper equipment to accurately test your alternator.
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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.

quitthaten

? to tjwalker...
have u personally used kelly's cables or put them on other vehilces? If so do u see significant improvements in voltage?

tjwalker

I have not. Generally speaking though, these cable upgrades keep your XJ supplied with consistent, reliable juice.

I borrowed that Renix ground piece from cruiser54; I'm sure he will chime in.

cruiser54

If you do the refreshing first, as described in Mr Walker's post, to the letter and with no shortcuts, it's an improvement.

Adding the cables as described is a notceable improvement.

Start there.

I have done an equivalent of Kelley's cables myself, only cuz I had the wire, and it's a real nice improvement. Were I to do another Jeep, I would just get teh stuff from Kelley. I know they would be nicer.

For now, the refreshing for sure and the optional cable replacement would be good to get on the way to solving the problem at hand.

quitthaten

I have taken my vehicle in for a dingnosis & the shop told me that i need a fuel injector replaced and my starter. I did get the starter replaced, it looked very rusty. They fuel injector I will be done this weekend. God Welling

NWhunter

I had a similar issue with my 94 Jeep Cherokee. 1 thing to keep in mind, The cherokee has auto off head lights. When mine wouldn't shut off, I replaced the headlight switch and problem was solved. Hope it helps

F1Addict

Newer Cherokees have auto-off headlights. quitthaten's '90 does not, as far as I know. This really does sound like a ground issue, which is a known problem on Renix era XJs. The fact that your old starter "looked very rusty" is an indicator that your grounds may also be very corroded. Try the ground refresh posted by TJ and let us know if it helped. My guess is that it will resolve your voltage issue.

cruiser54

On your Renix, replace all the injectors with the later style. The originals are known to leak fuel externally at a crimp and cause engine fires. Some guys on the forums sell them as does www.precisionautoinjectors.com.

And definitely do the ground refreshing as sugessted.