'87 Comanche won't start (sometimes)

[ian]

Hi, I've just recently bought an '87 Comanche L6 4.0ltr with a manual transmission, and it normally runs just fine, but it goes through spells where it won't start at all (unless push started) and then it will start up multiple times no problem, then again with the no starting, and so on... Had the battery/charging system checked, alternator is fine, battery is new and good, terminal connections look good etc.. so I'm down to a few things I think it could be, but since this is my first Jeep I am unsure.

 

1) perhaps the clutch safety switch has gone bad and needs to be replaced, or bypassed (not sure how to do this)

 

2) the starter solenoid may be going bad (maybe this is why it didn't show up on the scanner when i took it to the auto parts store)

 

3) possibly the starter itself is going bad? but read to be okay at auto part store...

 

Any thoughts?

 

Thank you.

 

-ian

[jimoshel]

Check the ground on the side of the block. Make sure it and the wires going to it are clean.

[Backdraft]

Flaky CPS maybe?

[ian]

Okay thanks I'll check the ground wire

 

CPS?

[cruiser54]

When you say it won't start, will it spin over but not start or not spin over at all?

 

You need to do this for sure:

 

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]

And this:

 

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, ECU, and some to the TCU, travel this path through the C101 connector.

 

The C101 connector 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 07-02-2012

[cruiser54]

And this:

 

Renix Jeep ICU/Coil contact refreshing

 

 

 

The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.

 

The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.

Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.

While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.

 

I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.

 

 

Revised 11-29-2011

[cruiser54]

This wouldn't hurt either:

 

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and adding dielectric grease before plugging it back together. Be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.

 

ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then dielectric grease should be added before plugging them back in. I do this on every Renix era Jeep I purchase or work on for someone else.

 

Revised 03/15/2012

[ian]

VERY helpful, thanks! Hopefully this weekend I'll have a chance to clean all the terminals and check wires etc, I appreciate all the help guys.

[cruiser54]

Keep us informed.

[JeffN]

if its a no crank, have someone hold the key in the start position while you tap the starter with a small hammer, if it starts the brushes or the commutator in the starter have gone bad

[ian]

will do

[ian]

it starts every time now, but the clutch went out on me today, going to tackle that beast this weekend.

[HOrnbrod]

Here we go again. I agree with everything Cruiser says except the use of dielectric paste on any shiny metal-to-metal contact in an electric connector, be it a single or multi-pin connector, high or low voltage, AC, DC, or high or low frequency RF. In every military electrical standard (MILSPEC) ever written the use of non-conductive pastes like dielectric grease is strictly verboten because of the resistance it creates.

 

Dielectric grease is non-conductive sealant and it's main purpose in life is to prevent contaminant entry (like H2O) into electrical connectors, spark plug boots, etc. You can use it on the connector shell or rubber boot, but never on the metal-to-metal connections. It will bite you in the butt over time.

 

There are many safe conductive paste products available that will seal contaminants out and not cause contact resistance like Kopr-Shield (best for copper-to-copper connections) or Ox-Gard (best for dissimilar metal connections).

 

Use dielectric paste it you like on shiny metal-to-metal electric connections. I don't and never will.

[Geonovast]

Just an FYI, the Renix system does not have a clutch safety switch. IIRC that wasn't a feature until 96 or 97.

[cruiser54]

Here we go again. I agree with everything Cruiser says except the use of dielectric paste on any shiny metal-to-metal contact in an electric connector, be it a single or multi-pin connector, high or low voltage, AC, DC, or high or low frequency RF. In every military electrical standard (MILSPEC) ever written the use of non-conductive pastes like dielectric grease is strictly verboten because of the resistance it creates.

 

Dielectric grease is non-conductive sealant and it's main purpose in life is to prevent contaminant entry (like H2O) into electrical connectors, spark plug boots, etc. You can use it on the connector shell or rubber boot, but never on the metal-to-metal connections. It will bite you in the butt over time.

 

There are many safe conductive paste products available that will seal contaminants out and not cause contact resistance like Kopr-Shield (best for copper-to-copper connections) or Ox-Gard (best for dissimilar metal connections).

 

Use dielectric paste it you like on shiny metal-to-metal electric connections. I don't and never will.

 

Here you go. Better?

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and adding dielectric grease around the perimeter of the connector to seal moisture out, before plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one. Be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.

 

ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then dielectric grease should be added before plugging them back in. I do this on every Renix era Jeep I purchase or work on for someone else.

 

Revised 07/17/2012

[HOrnbrod]

Here you go. Better? Revised 07/17/2012

Much. :cheers:

 

I'm not trying to be a tool Cruiser. I'm an old Grounding, Bonding and Shielding guy who worked for many years in military calibration labs all over and have seen the problems caused over time by using non-conductive pastes or grease on metallic electrical connections. very important stuff especially on aircraft. :eek:

 

The electrical cleaning and grounding procedures you detail are excellent. Unfortunately preventive maintenance like this is seldom done on a vehicle until a problem occurs. I for one thank you for taking the time to develop these procedures and posting them up. Keep pounding them in mate. :thumbsup:

[cruiser54]

Here you go. Better? Revised 07/17/2012

Much. :cheers:

 

I'm not trying to be a tool Cruiser. I'm an old Grounding, Bonding and Shielding guy who worked for many years in military calibration labs all over and have seen the problems caused over time by using non-conductive pastes or grease on metallic electrical connections. very important stuff especially on aircraft. :eek:

 

The electrical cleaning and grounding procedures you detail are excellent. Unfortunately preventive maintenance like this is seldom done on a vehicle until a problem occurs. I for one thank you for taking the time to develop these procedures and posting them up. Keep pounding them in mate. :thumbsup:

 

Should I just remove the dielectric from the write-up? I know you're not being a tool BTW!!

[HOrnbrod]

Probably, or some will be packing every connector that doesn't move with dielectric grease, or even Vaseline.

[cruiser54]

Better?

 

I suggest unplugging EVERY electrical connection in the engine bay you can find, whether engine related or not, and spraying it out with a good electronics cleaner, visually inspecting the terminals, and then plugging it back together. There’s a critical 10-pin connector for the front lighting system located in front of the air cleaner and behind the left headlight assembly. Don’t miss that one. Also be sure that the connectors to the ballast resistor mounted near the air cleaner housing are clean and tight.

 

ALL of the relays should be removed, the terminals wire-brushed until shiny, and the receptacles sprayed out with contact cleaner. Then plug them back in. I do this on every Renix era Jeep I purchase or work on for someone else.

 

Revised 07/17/2012

[cruiser54]

Modified this one too.

 

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, ECU, and some to the TCU, travel this path through the C101 connector.

 

The C101 connector 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 before bolting both halves back together.

 

 

Revised 07-17-2012

[ian]

by the time this Comanche got to me it was covered in dirt and rust, it's going to take some time to get it cleaned up, hopefully I can keep all the crucial parts maintained and tuned until I get time to do an over haul on the whole thing and bring it back to the life it once knew in its younger years. thanks again for all the advice guys.

[ian]

So I went to work on the clutch on Saturday, there must have been a factory crack on one end because the whole pedal broke off down near to where it connects to the rod that runs to the cylinder, I can take a picture of it later to show exactly what I'm talking about, it should be a difficult fix, just need a new master and slave cylinder and another clutch pedal to replace the broken one, problem..nobody in this area has that jeep, salvage yards included. Anyone have any idea where I could find a clutch pedal and the hardware that comes with it for an '87 comanche?