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School me on the 4.0 renix engine


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Just picked up a 87 Comanche with 4.0/5 speed. and looking to learn all i can about the renix. I noticed some things arent hooked up, and other lead nowhere. Truck runs good other then an exaust leak and high idle when first started up.

 

I'm no starnger to the 86 2.5l and 94 4.0 as i have both of those, but this renix is confusing at first glance.

 

Any advane would be great

Thanks

 

BTW here's some pics. :clapping: :clapping: :clapping:

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First thing to do when acquiring a Renix Jeep:

 

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 terminations 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 terminations. Inspect to see that none of the terminations 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 meta, clean and polish the cable termination, 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 termination. 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 16’ long with a 3/8” lug on each end works great and you can get one at any parts store already made up.

 

If you want to upgrade your grounds and battery cables in general, contact Jon at http://www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.

 

I have 5 or 6 other write-ups on the Renix that you may want to check out after doing the ground refreshing. They are all intended to address known factory issues and prevent issues down the road, and save you money from buying unneeded parts. And, they're free.

 

Here's another thing you'll want to do for sure:

 

Renix Jeep C101 Connector Refreshing

 

 

The C101 connector on 1987 and 1987 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

 

Almost every critical signal between the engine sensors, injectors, and the ECU travel the path through the C101.

 

The C101 is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.

Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.

 

If you have a small pick or dental tool tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter. Apply a true dielectric grease to the connection and bolt it back together.

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Thanks guys! that is the type of info i was looking for :clapping:

and how could i forget Billavista :oops:

 

Eagle, i didnt relize it was renix also, looks nothing like the renix engines i have seen in the past. open cooling system, very basic 2.5L i'll snap some pics of the odd stuff i see on the 4.0.

 

Also i press the brake pedel and my turnsignals light up, is this part of the bad ground issue?

Agian Thanks a million.

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Do the grounds first. Trust me. I was Service Manager and Shop Foreman at a Jeep dealership when these things were new. I kept a diary of sorts regarding prominent issues during that time. That's what I'm sharing in my first post-tried and true repairs for known problems. Little bit of time and no money buys you insurance for fewer problems in the future.

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He posted 1987 thru 1987 renix had the prob did you mean 87 thru 88?I ask because I have an 88 and just pulled the Booster today to do the WJ booster MC and I don't see the c101 bolt thats supposed to be there.Anyone have some pics to post?

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He posted 1987 thru 1987 renix had the prob did you mean 87 thru 88?I ask because I have an 88 and just pulled the Booster today to do the WJ booster MC and I don't see the c101 bolt thats supposed to be there.Anyone have some pics to post?

What are you asking?

 

There is no C101 "bolt." The C101 connector sits much higher than the brake booster. All '88s had it -- the change to delete it was a mid-year change in the 1989 model year.

 

What "prob" are you referring to? If you mean the C101 connector, it was removed on my '88 XJ and my '88 MJ still has it. I don't see any difference/improvement in the XJ for the $500 I paid a stealership to remove it.

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Do the grounds first. Trust me. I was Service Manager and Shop Foreman at a Jeep dealership when these things were new. I kept a diary of sorts regarding prominent issues during that time. That's what I'm sharing in my first post-tried and true repairs for known problems. Little bit of time and no money buys you insurance for fewer problems in the future.

 

thanks for the tip.

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He posted 1987 thru 1987 renix had the prob did you mean 87 thru 88?I ask because I have an 88 and just pulled the Booster today to do the WJ booster MC and I don't see the c101 bolt thats supposed to be there.Anyone have some pics to post?

 

 

1987 and 1988 had the C101 connector. It's mounted in the engine bay above the brake booster, on the firewall. The two halves of the connector are held together with a bolt in the center.

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If its a bolt that holds the c101 connector id call it the c101 bolt but maybe I'm crazy???.It needs cleaned not removed as said in the post.I was just tryin to figure out where it was so I can clean it while I'm there.I do my own work on my jeeps it involves research and saves me expensive trips to the dealer.

He posted 1987 thru 1987 renix had the prob did you mean 87 thru 88?I ask because I have an 88 and just pulled the Booster today to do the WJ booster MC and I don't see the c101 bolt thats supposed to be there.Anyone have some pics to post?

What are you asking?

 

There is no C101 "bolt." The C101 connector sits much higher than the brake booster. All '88s had it -- the change to delete it was a mid-year change in the 1989 model year.

 

What "prob" are you referring to? If you mean the C101 connector, it was removed on my '88 XJ and my '88 MJ still has it. I don't see any difference/improvement in the XJ for the $500 I paid a stealership to remove it.

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If its a bolt that holds the c101 connector id call it the c101 bolt but maybe I'm crazy???.It needs cleaned not removed as said in the post.I was just tryin to figure out where it was so I can clean it while I'm there.I do my own work on my jeeps it involves research and saves me expensive trips to the dealer.

On the firewall, in the engine bay, ABOVE the brake booster. There's a major wiring harness that runs parellel to the bottom of the windshield in that area. The C101 connector is the junction where the two sections of that big, fat bunch of wires snap together.

 

There was a TSB out on removing it, so there is a remote possibility that an '87 or '88 won't have it. If you look under the hood of my '88 XJ, for example, you won't find the C101 connector. (Of course, paying $500 to have it removed didn't accomplish any of the things that dealer's service manager told me it would fix. And when I mentioned that to him later he denied ever having said it would help anything. One more stealership crossed off my list.)

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Ahh ok I think I know now the original post said behind and above.Behind just kept sticking in my head so I was looking there.I have a thin metal bracket up there with a harness attached to it with a self tapping type screw.Thinkn maybe thats it???

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Possible answer to your brake/turn signal issue....

I use to have a couple dodge neons and they were known for having the same issue.

The fix was the turn signal assembly.

Not sure if its the same setup but for what its worth, hold the brake and mess with the turn signal arm and see if your lights go back to normal. If so then there's your answer.

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2 revised write-ups to replace the earlier first drafts I posted in this thread.

 

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

 

Renix Jeep C101 Connector Refreshing

 

 

The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

 

Almost every critical signal between the engine sensors, injectors, and the ECU travel the path through the C101.

 

The C101 is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.

Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.

 

If you have a small pick or dental tool tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter. Apply a true dielectric grease, not the stuff that came with your brake pads, to the connection and bolt it back together.

 

 

 

Revised 11-29-2011

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