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Unread 10-12-2011, 03:41 PM   #1
wrangin_myNeck
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No Spark!

Hi guys. Ive had some trouble in water with my 88 4.2L. Usually it will stall, then start after a few minutes. Yesterday it stalled but never started. We checked for spark, there was nothing. after reading a lot and printing this guide http://www.bobcat.ca/stuff/DOCS/DURATR~1.PDF and other steps I found posted by JeepHammer I got a new ICM but that did not solve my problem. I read that leaving the key in the on position for some time will cook the ICM and im assuming I may have added this to my problem yesterday while working on it.

I just purchased a new coil but I want to wait to install until I learn more about the external resistor. my stock coil has a yellow and green wire (= + -) and then another short yellow wire with an odd plug that goes nowhere. Is this where the resistor should be? ill get some pics now and post them.

I should tell you that I have done the nutter bypass and it worked successfully for around 150-200 miles. I believe I had the water problem before the nutter but Im not positive because I only drove the jeep about 40 miles previous to the nutter.

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Unread 10-12-2011, 03:53 PM   #2
wrangin_myNeck
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this is the picture of the plug that goes nowhere. I also followed these directions and the light was "Bright" so I am sure the resistor is gone.

Connect to battery NEGATIVE with a test light
Probe the coil connector 'positive' wire with a test light

"Bright" light means someone has removed the resistor wire
"Dim" light (Dimmer than testing the test lamp on the battery) will show you the resistor is working

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Unread 10-12-2011, 04:31 PM   #3
mcmud
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The short yellow (+) with connector is the capacitor jumper. A radio frequency 'Noise Suppression' gizmo.

The coil connector 'bright/dim' test should be done while the 'horseshoe' connector is pulled from the coil.
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Unread 10-12-2011, 05:13 PM   #4
wrangin_myNeck
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I believe we had the connector removed because we followed the directions step by step. is there anyway for me to know if that resistor is there? Any link on replacing the resistor? ive searched and found nothing

Another problem I had is with part 2 test 1 on the bobcat link. It says to measure resistance of ignition coil wire and replace if greater than 7,000 ohms. What setting should the multimeter be on, and if one probe is on the coil wire, where is the other probe contact point? Im assuming the "coil wire" is the wire going from top center of the coil to center of distributor.

Im still learning how to use the multimeter so any pointers are welcome
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Unread 10-12-2011, 05:39 PM   #5
mcmud
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Where the CJ used a 1.35 ohm resistor wire... I 'think' that the YJ resistor is mounted to the firewall or inner fender and that either system should allow 9.6 volts to the coil at the start.

These are more JH notes that may be of help;

************************************************** ****************************
If you know about electronics, you can't test a resistor unless you electrically load it.
You can't do that with a multimeter.

You have to connect to battery NEGATIVE with a test light,
Then probe the coil connector 'RED' wire with a test light.
The light is the 'Load' that will show you if the resistor is working.

"Bright" light means someone has removed the resistor wire,
"Dim" light (Dimmer than testing the test lamp on the battery) will show you the resistor is working.

Turn the key to the 'Run' position,
Probe the coil connector 'Red' wire,
This will tell you if your ignition switch, Ignition fuse, Factory Tach, ect are all working or not.
If you get power to the coil 'Red' wire,
And that lamp is 'Dimmer' than when directly wired to the battery terminals,
Then everything inside the vehicle is working and the 'Issue' is in the engine bay.

That one test lamp check is all it takes to verify your input to the fuse block, ignition fuse, ignition switch, factory tach and resistor wire,
And it tells you which side of the ignition the 'Issue' is.

************************************************** *****************************
------------------------------------

Hook test light to battery POSITIVE,
DISCONNECT coil connector,
Probe 'Green' wire terminal in the connector.

DO YOU GET A CONSTANTLY BRIGHT LIGHT?
If so, then you have primary ignition 'Ground'.
If you don't, then you ARE NOT getting primary ignition ground.

---------------------------------------
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Unread 10-12-2011, 06:03 PM   #6
mcmud
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Trace your yellow back to its source, the first component you encounter would be your resistor.

As to the 'how to' with anything electrical I'm the wrong person to be looking to for direction, a good indication as to why I have JeepHammer's notes stored, I'll excuse myself and hope that someone chimes in that can be of help... keeping one eye out to see that you get going and the other in hopes to learn.

Best of luck to ya. Have you thought about sending him a message...
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Unread 10-12-2011, 06:22 PM   #7
wrangin_myNeck
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I havent thought about sending him the message but maybe I will. I figured I would be able to find more on replacing the resistor since there are plenty of cases of people not getting spark. But thanks for your help, you always seem to come through with something when im at a loss. ill trace the yellow wire tomorrow and see where it goes.

and from your previous post im assuming the JH notes you posted are all with the connector unplugged?
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Unread 10-13-2011, 01:15 PM   #8
wrangin_myNeck
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Update!

Ok so i think i Made some progress (i hope). I put the new coil in today but it did nothing. Going back through JeepHammers notes I connected to Batt + and to the - lead on the coil connector...and no light. So the ground must be bad somewhere. My question is, can I just ground the coil to the battery or motor mount or do I need to trace the wire back and find the problem?

Id like to test the harness and I found these directions but dont quite follow them. Can anyone simplify these directions even more?

That is one test probe to the unplugged wire (unplugged on BOTH ends of it's run) and one test probe to 'Ground' to see if the wire is rubbed through somewhere and shorting to 'Ground' where it shouldn't be...
If the harness test out, then you are left with ONLY the module

Update again: I decided to ground the coil to the battery, and the terminal in the connector provided a ground when tested with a light as expected, but still no spark. I went back through and tested everything again and these are my results.

Coil connector positive wire test
  • My light didnt dim, meaning the resistor wire is broken or missing

Coil Connector negative wire test
*After adding the jumper from connector to negative battery terminal the light came on. But the OE green wire did not provide a ground


Crank the engine while testing the negative coil connector wire and look for blinking
*my test light did not blink, meaning the issue is on the engine bay side of the system. He says if it did not blink it is a bad module, bad trigger (stator) in distributor, no power to module, or bad wiring in between. It is a brand new module and I have power. Stator test also looked good, so bad wiring?

Test the resistance in stator in distributor by probing the two parallel blades in connector. Should show between 400-800
*The resistance was 598 so im assuming I can rule this out as a problem
[B]If the stator tests out go to module, pull two wire plug apart. look for zero volts at red wire with key switch off, and 12V with key in run[B]
*This checked out perfect, however I did not check for 12 volts at blue wire while cranking.

I checked for a good ground on the harness side of ICM plug and it grounds. This confuses me because the wiring diagrams show this as the same wire as the green wire at the coil which doesnt ground. So Im assuming my problem is the negative wire somewhere between the coil and ICM. Can I do anything except trace the wire all the way through the harness.
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Unread 10-13-2011, 02:47 PM   #9
mcmud
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Quote:
Originally Posted by wrangin_myNeck View Post
My question is, can I just ground the coil to the battery or motor mount or do I need to trace the wire back and find the problem?
No, don't ground the coil.

The ignition module ground is at the distributor via the black wire.
If you will add a splice into that wire and ground it somewhere along its path.... all the much better than original.
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Unread 10-13-2011, 05:45 PM   #10
wrangin_myNeck
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Quote:
Originally Posted by mcmud View Post
No, don't ground the coil.

The ignition module ground is at the distributor via the black wire.
If you will add a splice into that wire and ground it somewhere along its path.... all the much better than original.
ok thanks, I tried before I read your post and It didnt work anyway...hopefully I didnt mess anything up I hope its fine, it was just a ground.

This is the Diagram I have been looking at. the problem is this: the green wire is a good ground at the ICM connector but not at the ignition coil

I also added the ground to the black wire coming out of the ICM like he suggests.

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Unread 10-13-2011, 06:40 PM   #11
mcmud
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Quote:
Originally Posted by wrangin_myNeck View Post
ok thanks, I tried before I read your post and It didnt work anyway...hopefully I didnt mess anything up I hope its fine, it was just a ground.

This is the Diagram I have been looking at. the problem is this: the green wire is a good ground at the ICM connector but not at the ignition coil
The (-) negative terminal at the coil is not a ground, the coil is internally grounded.

Saved JeepHammer notes;
---------------------------------------

The biggest test I need you to do is the constant 'On' light on the 'Green' wire without it being hooked up to the coil.

This will tell me if the module is grounded.

I already know the light doesn't flash when cranking,
But I need you to test the same circuit without cranking to know if the module is grounded sufficiently to make a 'Bright' light when you test it.

If you don't get a 'Bright' light when connecting to the 'Green' coil connector terminal,
Then you have a VERY bad module,
Bad "Green" wire between coil and module,
Or a bad 'Ground' to the module.

We are just ruling the 'Green' wire and ground circuit out of the list of potential 'Issues'...
-----------------------------------------------


Check the green at the (disconnected)horseshoe connector while the ICM connection is made.
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Unread 10-13-2011, 07:05 PM   #12
wrangin_myNeck
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Thanks mud. I have done this test and I get no light from the green wire at coil connector, with connector disconnected. Since I just replaced the ICM I'm leaning towards the bad wire. I also added the ground wire he advises to a motor mount so the module should be grounded.

Would it be wise to get some 16g wire and just run it from coil connector to the harness side of the ICM plug? It's much faster than pulling the main harness apart just to find, or not find the bad spot.
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Unread 10-13-2011, 07:20 PM   #13
mcmud
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Quote:
Originally Posted by wrangin_myNeck View Post
Thanks mud. I have done this test and I get no light from the green wire at coil connector, with connector disconnected.
Twice, this is not clear if the test was done while the connection was made at the ICM... if that was the case and that connector terminals are clean, then you might run a wire between the coil and ICM connectors for the sake of testing, but I think you should remove that section of green just to be sure that it hasn't rubbed raw in the loom with the potential of causing other issues.

Quote:
Since I just replaced the ICM I'm leaning towards the bad wire. I also added the ground wire he advises to a motor mount so the module should be grounded.

Would it be wise to get some 16g wire and just run it from coil connector to the harness side of the ICM plug? It's much faster than pulling the main harness apart just to find, or not find the bad spot.
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Unread 10-13-2011, 08:05 PM   #14
wrangin_myNeck
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Oh sorry, I didn't realize I wasn't clear with that. Yes the ICM was connected. Everything was as it should be for the vehicle to run except for the coil connector being unplugged.

The green wire gave me no light with the key set to "run" and no light or flashing while cranking. You raise a good point about a frayed wire causing more problems. I will try running a test wire from coil connector to ICM tomorrow and report back. Thanks again for the help!
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Unread 10-14-2011, 12:50 PM   #15
wrangin_myNeck
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ok so today I went through the entire harness (in the rain, brought a whole new meaning to working "under the hood" ) and inspected the green wire from coil connector to ICM connector. The wire looked fine so I did a continuity test from plug to plug and it read .5, I then tested a spare length of new wire and it also tested .5 so the green wire is fine.

Although I just replaced the ICM I am thinking I may have been given a bad one from the store so I just took it back and they will have a new one for me tonight at 6.

I also performed these tests I found in another thread posted by JeepHammer:

"I'd have a strong look at the 'Green' wire with a multimeter.
I would DISCONNECT the distributor connector so the module can't get 'Ground',
Then I would check the 'Ground' (Green at the coil connector, or black at the distributor connector, harness side both places) to see if there is contunity to 'Ground' (engine block).

This test will tell you if there is an issue with insulation, connectors, ect.
Once coil and distributor are DISCONNECTED from the harness,
Connect to the harness and the engine block and check for resistance.
You should show infinate resistance, no connection at all.

If you show ANY contunity between the wiring and the engine block, then you have a 'Sneak Circuit' or 'Short Circuit' showing up and you need to find the connector/wiring insulation break causing that issue.

Keep in mind, about 25% of the modules I buy at the 'Discount Sore' are bad right out of the box...
And another 10 to 20% fail very quickly after installed.
The quality of those discount modules are so poor they are virtually useless..."


Nothing showed continuity So I am hoping its safe to say there are no 'short circuits' in my harness anywhere. Ill report back after I try the new ICM
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