Engine Stalls

[2360]

On two occasions (couple of months apart) my engine (4.0L  88 Comanche) stalled and would not start.  Both times I could not hear the "whiz clunk" when turning on the ignition.  Both times after a few hours later the engine starts as per usual. On each occasion it was fairly hot day.

 

I'm guessing a number of possibilities,  faultly fuel pump, poor ground on fuel pump,  cps or poor cps ground.

 

Just wondering if anyone has had an identical problem, be nice just to cut to the chase.

 

Thanks.

[88whitemanche]

Try checking the ground behind the left taillight lamp...unscrew it, shave the paint to bare metal and reinstall the ground to see if that works....

[1989 Eliminator]

I have a 89 and I had the same symtomps of you and for me it was the CPS. I went and got a CPS from a local MOPAR dealer not a crappy CPS from an outo parts store. That will eventually fail again. There was no signal going to the ICM to tell the coil to give spark to the spark plugs.

 

Take a look at Cruiser54's page and find the CPS testing. His profile picture actully shows the CPS and where it is! http://comancheclub.com/user/2838-cruiser54/

[2360]

Well, I'll try the ground by the taillight first.   I'm wondering if the CPS goes if that would affect the fuel pump not whiring up when the ignition is turned on.

 

[cruiser54]

Well, I'll try the ground by the taillight first.   I'm wondering if the CPS goes if that would affect the fuel pump not whiring up when the ignition is turned on.

 

No. The CPS gernerates it's own signal to the ECU independent of all other systems.

 

You can test it. A goos ground refreshing, connector refreshing, C101 cleaning if applicable, coil to ICU refreshing should all be done. Those are covered in the link in my signature with photos. Do the ground behind the taillight for sure.

[2360]

 

Removed taillight and tried to remove ground screw with Philips screwdriver.  No go.  Had to use vice grips to turn the screw.  After disconnect, tried the ignition, no fuel pump noise.  Wow. Once again so much depends on just a little thing.  Cleaned the screw, ground wire connector, and screw hole and put some grease ground stuff on it.  I'm hoping that's the cure, time will tell.

Thanks guys for the input.  :thumbsup:

 

Here's a snap of my new deck and the paint job on the dash.

 

[cruiser54]

Simple fixes are the best. Keep us in the loop.

[2360]

Well, truck stalled again yesterday.  So I guess it's not the ground wire behind the taillight.

 

Next option is the fuel pump, not what I want to change, but I guess after 528 k's it's due. 

[2360]

Here's the latest:

 

Changed the fuel pump ( :mad: only good thing about that job is should be easier 2nd time around) and the truck wouldn't start.  Next day truck started as if nothing was wrong. 

Took out the ECM, (that wasn't easy either) checked and put some di electric stuff on the connector. Replaced the relay for the fuel pump. Played around with ballast resistor.

 

Waiting to see if the truck dies a third time.  Hopefully it won't be -20 if it does. 

 

Oh, sidenote: when replacing the fuel pump the fuel screen on the pump fell off into the tank, :doh: so I'll see what that does to the fuel pump life.

[skel130]

You can check the fuel pump's output under the hood. The fuel rail has a Schrader valve that you can hook a fuel pressure gauge upto. I don't know the exact spec, but I'm sure your chilton's or hayne's manual has it. Next time it doesn't start, check spark under the hood. My old man always explain an engine as needing 3 things: fuel, air, and spark. Narrow that sucker down. If your fuel pressure is fine, then don't bother with fuelpump/filter/injectors. Spark is my suspect.

[cruiser54]

Here's the latest:

 

Changed the fuel pump ( :mad: only good thing about that job is should be easier 2nd time around) and the truck wouldn't start.  Next day truck started as if nothing was wrong. 

Took out the ECM, (that wasn't easy either) checked and put some di electric stuff on the connector. Replaced the relay for the fuel pump. Played around with ballast resistor.

 

Waiting to see if the truck dies a third time.  Hopefully it won't be -20 if it does. 

 

Oh, sidenote: when replacing the fuel pump the fuel screen on the pump fell off into the tank, :doh: so I'll see what that does to the fuel pump life.

Have you done the ground refreshing and connector refreshing?

[2360]

Have you done the ground refreshing and connector refreshing?

 

Nope, but I think I've had the connector apart years ago.   Looks like that's my next task which will happen when the snow disappears and it warms up a bit.

[cruiser54]

These are in the link in my signature, but I'll post them up here for you. KNOWN issues with the Jeeps. Simple fixes.

 

     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

 

 

 

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

 

 

 

 

 

Cruiser’s Renix Sensor Ground Test

This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.

Set your meter to measure Ohms. Be sure the key is in the OFF position.  Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.

Revised 06/12/2012