Guys A Not Starting Problem

[banshee]

Only random firing

checks 3.41VDC from ECU to CPS and back to ECU is this normal? O and with a meter i can't see it change states, meaning hi/low

second with the CPS unplugged i read voltage on BOTH sides from ECU is this normal?

HELP thinking ECU toast, but it will try to start once in a while after coolinig off but never dose

 

my manche left me walking

[cruiser54]

What year, engine etc?

 

Not the way to test a CPS on a Renix at least, if that's what it is.

[87manche1]

Per old post he has an 87 so renix. check cruisers his link .what happened ur lsst no start in 2012.

[banshee]

2012 replaced CPS from NAPA and yes 87 renix

Per old post he has an 87 so renix. check cruisers his link .what happened ur lsst no start in 2012.

[banshee]

update 5-4-13 if already known please forgive the repost

so replaced CPS, distributor, and coil, that all being said still having inconsistent firing

starts fine runs smooth for about two minutes then just died no sputter, not hesitation

just like key shut off???

Now still troubleshooting issue here’s what I’ve found so far, if your CPS is out your injectors will not fire, nor will your coil, the same with your ECU the same input allows the signal output to the injectors and the coil, so either coil depending on resistance may or may-not be bad, ignition module can also cause the same issue…

Where to go from here???????????? B…

[cruiser54]

TEST the cPS:

Renix CPS Testing and Adjusting

 

Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.

You should get a reading of  .5 AC volts.

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs  (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!!  That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

Revised 01-26-2013

[cruiser54]

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 making sure they haven’t retracted into the plastic holder, 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 Jeep I purchase or work on for someone else.

Revised 07/23/2012
 

[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, 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
 

[cruiser54]

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  ¼” 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 03-02-2013
 

[cruiser54]

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 and some fine sandpaper.
Squeeze the springy contacts closer together with some needlenose pliers. 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.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.

Revised 04-04-2013

[banshee]

thanks cruiser good info,

what i haven't already done, I'll try

 

thanks B...

[cruiser54]

You can always click on the link in my signature and read them all.

[banshee]

update ignition module replaced and what do you know

started and most important stayed running thanks for all your help

and cruiser you keep posting  WE need it.... B...

[cruiser54]

update ignition module replaced and what do you know

started and most important stayed running thanks for all your help

and cruiser you keep posting  WE need it.... B...

Do those things anyway, even though you found the problem this time. It can save you headaches in the future.