Mudboi222

Hey guys. Ive been kind of bored lately and just been trying to fix some issues ive had going on with my Jeep. Here lately, it happens every now and then but whenever i get on it in my Jeep its kind of sluggish? Like i can almost put it to the floor and it spits and sputters then out of no where it will pin you back in the seat. Like i said it barely happens but i have come to think it might be my fuel pump? Here lately ive noticed when i leave my Jeep running and get out i can here a pretty loud hissing/sucking noise coming from the back of my Jeep right at the gas tank. If anyone has a idea could you help please?

Oh and also whenever i get on it sometimes, for instance i have my air on. When i get it my air quiets down and voltage drops a little bit and my lights dim a little. Then when i let off my air gets back louder and all my lights get brighter. I just had a alternator rebuilt by Caterpillar. My dads work owns a huge boat and has the have the alternators rebuilt every month because of the power they generate. But i know for sure the alternator is good. I get it tested every now and then for the hell of it.

Anyways, any help or recommendations would be awesome! Thanks guys!

cruiser54

Sounds like the fuel pump is dying if it's making the hissing noise.

As for your electrical issues, do the following to start off with:

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, failed emission tests, and wasted money replacing components unnecessarily.
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 03-04-2013

Mudboi222

Thanks Cruiser once again, I fixed my electrical issue. I just wire burshed all my grounds i could find. Im gonna get a new fuel pump and filter this Friday. I do a lot of wheeling & ive heard the Fuel Pumps at the part stores suck for that kind of use?

cruiser54

Fuel pumps are fine from the parts stores as long as you stay away from Airtex.

Did you remove the wires from the ground points during cleanining BTW?

Behind the spare tire, under the plastic trim panel is your fuel pump and sending unit ground fWIW.