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Unread 04-22-2013, 05:20 AM   #1
stilllearning6
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Intermittent ground primary circuit?

Symptoms: driving 30 mph , stalls.
Sometimes , it will only miss and continue.
Sometimes it stalls and usually immediately restarts.
Every once in a while it needs to sit and then restart.

Replaced Autozone PN F-133 Ignition Control Module several times to no avail. I hear that these are notorious for failures. Not sure.

Suspect that I am dropping the primary circuit ground.

How many and where should I redo the grounds?

I suspect the distributor has a ground somewhere internally
( where , what to look for? ) that needs a redo.

I suspect that the engine block has a ground that needs a redo.

Would appreciate any confirmation / guidance.
Am prepared to redo the grounds with dielectric grease.

Perhaps I am looking in the wrong place.
I see the internet is full of 258 / carb /MCU stall postings.
Do not feel that it is carb issue at all.
Tach drops to zero immediately and gives no signs of stumbling .
Abrupt cut-out of ignition.

This issue has persisted for years.
Four mechanic shops have been unable to solve.
In pursuing the cause, replaced:
distrib cap, rotor, plug wires , pickup coil, MCU, ICM, ignition coil,carburetor remanufautured.

Is there a recurring short /drop ground inherent in this 258/ carb?

It is my understanding that the MCU bypass would not solve this .
As I understand the Nutter Bypass, it removes the fine tuning controls of fuel/air mixture and of timing; it does not address a massive failure.
Am I incorrect or correct about that ?

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Unread 04-22-2013, 06:21 AM   #2
Que89YJ
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The fact the tach drops to zero is a huge clue. You could have an issue at the column with switched power. I would try a little discovery trouble shooting with jumpering power to the coil from your battery and see if it still does it. It is a little difficult trying to track down intermittants.

No you aren't correct. The nutter bypasses the computer and emissions and gives you a local ground for the distributor and the ecu. I would strogly suggest doing the nutter bypass. It is very simple. 3 wires to try it out and see if it makes any difference. It is by far the best thing you can do to your jeep for simplifying and dramatically improving your 258's ignition system.
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Unread 04-22-2013, 06:53 AM   #3
stilllearning6
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Thank you QUE89YJ .
Can you educate more about the column theory.
It sounds as if you are referring to the on/off ignition switch.

I am trying to understand the theory / wiring to follow.
The tach drops immediately to zero provides what critical info?
I am guessing it is electrical due to the tach behavior , Jeep does not stumble , just dies while driving.

Are you suggesting running a wire from pos or neg battery terminal to which terminal at the ignition coil ?
My guess is positive battery to positive ignition coil ??

So the Nutter also reroutes the ground .
I have been evaluating Nutter for years and have resisted as the stock system of sensors / vacuum have been meticulously restored over the years and the jeep starts right away , runs smooth . I believe ( could be wrong) that the electrical intermittant issue is traceable to its root cause .

I appreciate your comments . This has been a struggle .
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Unread 04-22-2013, 07:12 AM   #4
dancytron
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The black wire that runs from the ignition control module to a bolt under the distributor is a ground for the ignition and not a very good one. Splice in and ground it to the negative battery terminal and see what that does.

This is part of what que was talking about, but you don't need to do the rest of the Nutter to improve this ground.

edit: posts overlapped. if yours has really been maintained like you say and has the stock carb, then you probably don't need to do the Nutter.
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Unread 04-22-2013, 07:19 AM   #5
stilllearning6
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Dancytron- thanks for the ground guidance and for the Nutter info.
Will attempt to re-establish clean ground at distrib for the ICM.
Question : Is the Diagnostic Connector Box #1 , terminal #3
( the smaller of the 2 yellow plastic covered items near battery )
helpful to assess the ICM ground ? I was hoping to ohm it out as I wiggle
the distrib black ground wire and hope that I
see a drop of the ground. That would be great to isolate the cause.
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Unread 04-22-2013, 08:22 AM   #6
Que89YJ
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You really should do the nutter bypass. I can't stress how big a difference it is. The only reason I can see for not doing it is if you have an emissions requirement. If not then seriously do it.

Have you checked the starter relay and the fuseable links on the firewall? I suggest you try and move the wiring in and around your relay and the fuseable links looking for a bad connection. It is the central supply for everything.

As far as jumpering power the easiest way to do it is start at the starter relay on the firewall. Keep in mind this is a troubleshooting measure and it must be disconnected when powering off. Run a small jumper wire on the relay from your battery terminal to your ignition terminal. You need to work around the exsisting wires and remember to be careful you dont want to short out anything.
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Unread 04-22-2013, 11:17 AM   #7
stilllearning6
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Que89YJ : Would poor connections at the starter relay cause the symptoms of stall while cruising ?
I can certainly redo those connections.
The Jeep seems to fire up right away after most of the stalls.
The immediate startup is why I did not consider the starter relay .
Perhaps a gross mistake.
I am still learning .

I do appreciate the experience of others who are far more knowledgeable than I .
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Unread 04-22-2013, 11:38 AM   #8
Que89YJ
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The ignition switch dropping can if you have a bad switch. Jumpering power from the battery should work to let you know if the issue is an ignition issue. Next step would be power directly to the coil. Do the shake test on the wiring harness and fuseable link off the starter relay. Again, think about the nutter if you dont have emissions. It is amazing what a difference it makes.
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Unread 04-25-2013, 05:32 AM   #9
stilllearning6
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Replaced ICM and rotor yesterday , cleaned inside /outside distrib cap.
Jeep fired right up as usual.
This time ran one hour at idle w/o stall , and then , drove 15 mph around local roads;no problems.
That was a big improvement.

Tried to cause a drop of ground via wiggling distributor black ground wire at the base of the distributor and also wiggled the harness connection of the yellow and green wires.
Jeep still ran fine.

Tried to cause a drop of connection via wiggling ignition coil + / - wires.
Jeep still ran fine.

I will not know for a while if the stall issue was resolved as it was an intermittent issue.

I am appreciative of the efforts to assist me; this forum teaches me many things.

I had trouble tracing the distributor black grounding wire to its engine block connection.
Is it at the rear of the engine where there are several other grounds?

My fingers could not follow the distributor black grounding wire as it wrapped between the distributor and just below the valve cover.
Is the black distributor ground wire connected to the base of the distributor in a secret hidden place with its own screw/ bolt ?

I like the idea of the dedicated ICM grounding wire and plan to do that next if the Jeep should stall this week.

Where do most folks splice into the existing black ICM ground wire?
I guess that it might be between the ICM harness connector and the distributor ??

Much thanks for your guidance.
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Unread 04-25-2013, 09:36 AM   #10
dancytron
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I believe the reason you can't find a ground to the engine on the black wire between the ICM and the distributor is because there isn't one. It is just grounded by the bolt below the distributor.

I made a grounding post connected to the negative battery terminal with a 4 gauge cable and grounded the ICM, Alternator and other stuff to it. Search Jeephammer and grounds in the CJ forum. I basically followed that.

I think anywhere between the ICM and distributor is okay for splicing into the black wire. It made a noticeable improvement on how it ran for me.
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Unread 04-25-2013, 11:23 AM   #11
stilllearning6
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Thank you .

If a stall happens, will post back and try the splice grounding wire.
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Unread 04-25-2013, 01:48 PM   #12
Que89YJ
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Sounds like you got it. Look at the nutter.
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Unread 04-25-2013, 04:51 PM   #13
Old4X
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If you look under the distributor cap, you will see a brass grommet with a screw in it that secures the pickup coil.

Your ground path from your black wire leads here.

The ground then utilizes the body of the distributor and grounds via the hold down clamp securing the distributor to the block.

Quick and cheap way to ground the ICM on the assembly line, after 25 years it is somewhat lacking due to crud, corrosion, etc.
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Unread 04-25-2013, 06:32 PM   #14
stilllearning6
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Old4X - Super info. Now, I understand the grounding pathway. Thanx.
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Unread 04-25-2013, 08:06 PM   #15
jay-h
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Quote:
Originally Posted by stilllearning6 View Post
Que89YJ : Would poor connections at the starter relay cause the symptoms of stall while cruising ?
I can certainly redo those connections.
The Jeep seems to fire up right away after most of the stalls.
The immediate startup is why I did not consider the starter relay .
Perhaps a gross mistake.
I am still learning .

I do appreciate the experience of others who are far more knowledgeable than I .
All the power for the system comes through that screw terminal on the relay. So that could cause a problem, however one would expect the lights and other accessories to be affected also.

Engine ground is not likely the culprit, because that is accomplished with a big wire (to carry starter current). If that were bad, you'd have starter troubles.

I think there is some likelihood that you are having intermittent power to the spark module (could be steering column switch or wiring). The red wire (as I remember) on the spark module should be continuous hot during running. I would tap a voltmeter into that line and have it in the cab with you. When the trouble occurs, see if you still have power at that connection.
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