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Unread 06-05-2010, 01:42 PM   #1
Ken4444
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258 turns over, but no spark

1985 CJ7, 258 engine, manual trans

I'm not sure what changed to cause this. I was troubleshooting the non-functioning factory temperature gauge and checking for voltage at various places along the purple wire. At one point I took apart the two parts of the electrical connector that goes through the firewall, but it re-assembled without problems. It had (black) grease on all the terminals, but no corrosion as far as I could see unless that's what the black stuff was.

Later that night the Jeep would crank but not start.

I replaced the ignition module and that didn't help. The "old" one didn't look that old anyhow.

I'm not getting a spark at the first (front) plug. I did not check the others. The wire from the coil to the distributor was green at the coil. I cleaned the coil and wire. No change. Ironically I have new wires and a new coil on the way.

The wire broke off the capacitor near the coil, so I soldered that back together but the thing is so old I have no idea if it's even functioning. It's my understanding this is only needed to keep electrical noise out of the stereo system, so I don't think this is the problem.

When I turn the ignition to "on", I get about 12.5 volts to the red wire going to the coil, so that seems right. The green wire to the coil comes from the Ignition module, so I'm not sure how to check that.

The battery gives me about 12.5 volts. The headlights and parking lights work.

Obviously I need to replace the coil, along with the other parts I have on order for the Team Rush.

I could check to see if I'm getting no spark right out of the coil.

What else might cause no spark? Is there anything else I should be checking?

Thanks!

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Unread 06-05-2010, 03:25 PM   #2
Mike Romain
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I would first be thinking one of the wires had a weak hold down tab and backed out when you put the bulkhead connector together. I have seen several wires back out doing that.
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Unread 06-05-2010, 07:03 PM   #3
Ken4444
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Quote:
Originally Posted by Mike Romain View Post
I would first be thinking one of the wires had a weak hold down tab and backed out when you put the bulkhead connector together. I have seen several wires back out doing that.
I disassembled the bulkhead connector again and inspected it. The tab for the purple wire was bent. I straightened it and it re-seated correctly, but the original problem remains.

I installed a new coil but am waiting for a helper to assist with seeing if I'm getting any spark now.

Is there any reason to doubt the starter solenoid at this point? The engine seems to turn over OK so I'm thinking the solenoid is fine, but perhaps I could check that the "I" connector on the solenoid is giving 12+ volts when the engine cranks.

Does anyone have a list of the wires that travel through the bulkhead connector?
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Last edited by Ken4444; 06-05-2010 at 07:34 PM..
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Unread 06-06-2010, 07:52 AM   #4
Mike Romain
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Here is the FSM with wiring schematics: 84-86 Factory Service Manual... - JeepForum.com

John Strenk has posted photos of the bulkhead connector all marked I believe and this:
bulkheadconnector.jpg  
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 06-06-2010, 09:25 AM   #5
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First off,
Test for spark at the coil wire.
More strikes per revolution of the engine, easier to determine if the coil is firing or not.

Secondly,
Get yourself a test light so you can actually LOAD the resistor wire and tell if the module is triggering the ignition or not.
They run about $6 at the parts stores.

Third,
Pull the coil connector off the coil,
Test the 'Green' wire in the connector.
Connect to battery POSITIVE with the test light,
Then probe the 'Green' wire coil connector.

With the engine CRANKING, you should get a flashing light.
If you don't,
The distributor trigger, ground to the module or module is bad.

If you do get a 'Flashing' when cranking the engine,
Then you probably have a bad coil, coil wire, distributor cap or rotor.
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Unread 06-06-2010, 11:00 AM   #6
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Quote:
Originally Posted by JeepHammer View Post
Secondly,
Get yourself a test light so you can actually LOAD the resistor wire and tell if the module is triggering the ignition or not.
Thanks for the assistance. I do have a test light and will carry out these steps today. Can you elaborate on step 2? The only resistor I'm seeing in the schematic is the 'Closed Throttle Resistor' which I don't think is the one.

I'm assuming I need to put the test light in series with the resistor wire?

Thanks!
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Unread 06-06-2010, 01:06 PM   #7
JeepHammer
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There is a 1.35 Ohm resistor wire in your harness going to the ignition coil positive terminal.

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.

---------------------------------

Then you connect your test lamp to battery 'Negative' and probe the 'Green' wire terminal in the coil connector.

If the test lamp lights up 'Bright' right away,
Then you have verified the ground path through the module, through the engine wiring harness, through the distributor housing, through the engine block, through the ground lug connection back to the battery.

When you crank the engine while testing the 'Green' wire,
That will tell you if the distributor trigger is working sending signal to the module,
The module is processing that signal,
And the module is correctly switching 'On' & 'Off' the coil so it will generate the secondary high voltage to the distributor cap/plugs.

It's a VERY Simple way to split/test the entire ignition system very quickly.
But for some reason, people want to whip out a voltmeter and try to do it the hard way...

Voltage reading will lie to you since the more current you draw though the resistor, the warmer it will get and the more resistance it will throw.

Voltage doesn't matter anyway.
Between the bad battery connections, the 30 year old wiring connections, corrosion, cob webs, previous owner hacks, the factory using duct tape on electrical circuits, wear on/crud in the ignition switch, ect. you don't know what you are going to come up with for voltage,

So a simple 'Yes/No' way to test for enough current is a simple solution.

If you don't find the module switching (Flashing Light While Cranking) then you have an issue on the ignition side(engine bay) of the system.

If you don't get power to the coil with the ignition switch in the 'Run' position,
Then you probably have a blown fuse, factory tach not working, broken resistor wire, ect.
Cuts your search in half with one simple test.
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Unread 06-06-2010, 03:31 PM   #8
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Okay, I have completed the three tests. Here are the results:

Quote:
Originally Posted by JeepHammer View Post
First off,
Test for spark at the coil wire.
More strikes per revolution of the engine, easier to determine if the coil is firing or not.
There was one spark, then nothing, even with the engine still cranking. I repeated the procedure a second time and it was the same: one spark, then nothing.

Quote:
Originally Posted by JeepHammer View Post
Secondly,
Get yourself a test light so you can actually LOAD the resistor wire and tell if the module is triggering the ignition or not.
They run about $6 at the parts stores.
The probe was dimmer when testng the red coil wire than it was when getting power directly from the battery. During this test I left the red wire connected to the coil.

Quote:
Originally Posted by JeepHammer View Post
Third,
Pull the coil connector off the coil,
Test the 'Green' wire in the connector.
Connect to battery POSITIVE with the test light,
Then probe the 'Green' wire coil connector.

With the engine CRANKING, you should get a flashing light.
If you don't,
The distributor trigger, ground to the module or module is bad.

If you do get a 'Flashing' when cranking the engine,
Then you probably have a bad coil, coil wire, distributor cap or rotor.
The probe light did not flash on/off, or bright/dim. It did dim initially when the starter motor started cranking, but after that the test probe light stayed on and even.

All this would suggest, as you said, that "The distributor trigger, ground to the module or module is bad."

I have replaced the ignition module. According to the schematic, it has a black wire to ground. I can trace this and see what it looks like, or give it a temporary good ground to see if that changes the problem.

That is the 'distributor trigger'?
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Unread 06-06-2010, 04:11 PM   #9
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Based on the diagram in this similarly named thread...

http://www.jeepforum.com/forum/f8/25...6/#post5552499

...the Ignition Module gets its ground from the distributor. Seems like a long way to go for a ground. What if I splice in a ground wire and ground it to the firewall? My Jeep already has some things grounded there anyhow.
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Unread 06-07-2010, 05:23 AM   #10
Mike Romain
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Quote:
Originally Posted by Ken4444 View Post
Based on the diagram in this similarly named thread...

http://www.jeepforum.com/forum/f8/25...6/#post5552499

...the Ignition Module gets its ground from the distributor. Seems like a long way to go for a ground. What if I splice in a ground wire and ground it to the firewall? My Jeep already has some things grounded there anyhow.
I went right to the battery negative for my ground.

The pickup in the distributor can be tested. 400-800 ohms between the orange and purple wires with 600 being best.
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 06-07-2010, 06:23 AM   #11
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Quote:
Originally Posted by Mike Romain View Post
I went right to the battery negative for my ground.

The pickup in the distributor can be tested. 400-800 ohms between the orange and purple wires with 600 being best.
Last night I grounded the Ignition Module to a clean screw on the firewall but this did not change the problem. I will run a temporary ground to the battery to see if this helps.

I will also test the resistance across the distributor pickup tonight.

What does it mean when the coil gives one spark, and then nothing? This seems like it would indicate a problem with the Ignition Module, as the ignition module looks like it directly feeds the coil via the green wire. Test #3 above (test signal from green wire), would indicate there is a problem from the Ignition Module. Assuming that my ignition module is good (bad assumption, I know), since I just replaced it, I suppose the grounding issue might be in question. What else in the ignition module can be tested? I suppose all of its other wired contacts are potentially failure points too.
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Unread 06-07-2010, 06:45 AM   #12
Mike Romain
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The green wire is the trigger signal wire.

You have a pickup, the module and ug, a computer that has a lock on this signal.

Using a test light to trace circuits on a computer controlled vehicle has been known to kill the computer by adding 12 volts to a 5 volt signal line, thus cooking electronic parts. I was taught in College you should only 'mess around' with a multimeter. Now testing a specific part with a light is still fine, it is just those 'other' wires that can cause trouble.

If the pickup tests out ok, then you can bypass the computer by hooking the orange and purple wires at the module directly tot he orange and purple at the distributor with two new wires twisted together for rf. if it then starts, you can leave it and reset the timing and carb and drive like that. See: How to - Nutter Bypass - JeepForum.com for directions on doing this and cleaning up the vacuum lines.
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 06-07-2010, 07:02 AM   #13
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OK,

FIRST!
When I say to remove the coil connector from the coil....
Well, it should be obvious...

Secondly.
When you connect to battery positive with the test light,
Then probe the 'Green' coil CONNECTOR wire
(NOT THE COIL WHICH SHOULDN'T BE HOOKED UP...)

Do you get a 'Bright' light when you probe the green wire?

If not, then you have an ignition module 'Ground' issue.

That constant bright light tests the ground circuit just like I told you before.
--------------------------------

Then, still probing the coil CONNECTOR (Coil Disconnected) did you get a flashing light when cranking the engine?

If you did, then the module, trigger, and all the engine wiring is working.

IF you DID NOT get the flashing test light,
Then you have a bad module, bad trigger (Stator) in the distributor, no power to the module,
Or bad wiring in between.
-----------------------------------

ONE SPARK means you are getting power from the key switch like you are supposed to.
The coil is saturating when you turn the key on,
And it's firing when you turn the key off.

What we need to determine is why your module isn't turning the coil 'ON & OFF' like it's supposed to...

And you aren't going to find the 'Issue' if you keep ignoring the proper test procedures!
------------------------------------

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.

---------------------------------------

Hook test light to battery POSITIVE,
Disconnect coil connector,
Probe 'Green' wire terminal while cranking engine.

DO YOU GET A FLASHING LIGHT?
If so, the module is triggering the coil to fire, and you have a bad coil.
If not, You have a failure in the 'Trigger' (Stator), Module, or wiring in between the two.

----------------------------------------

Once you have results from this one simple test, we can track down the 'Issue'!
We can't do anything until you perform that test and report back...

When you leave the coil in the circuit, you leave a vairable that can't be easily diagnosed,
The coil MUST be unhooked!
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Unread 06-07-2010, 07:10 AM   #14
JeepHammer
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Quote:
Originally Posted by Mike Romain View Post
The green wire is the trigger signal wire.
Mike, there is no 'Trigger Signal' with a transformer coil.

That green wire simply goes to the module, and the module opens the coil circuit.

Positive is still coming from the key switch to/through the coil, but the 'Ground' leg of the circuit is opened.

Once the circuit is opened, the magnetic field collapses and creates the secondary spark energy in the secondary windings.

If we start calling it a 'Signal', then I'm afraid we'll start getting people confusing it with the signal from the stator in the distributor, and this is already hard enough for most folks to grasp...

You have a pickup, the module and ug, a computer that has a lock on this signal.

Quote:
Using a test light to trace circuits on a computer controlled vehicle has been known to kill the computer by adding 12 volts to a 5 volt signal line, thus cooking electronic parts. I was taught in College you should only 'mess around' with a multimeter. Now testing a specific part with a light is still fine, it is just those 'other' wires that can cause trouble.
I'm only using the test light to load 12 volt capable circuits,
Ignition switch, ignition coil circuit, ect.

I wouldn't ask them to probe timing computer terminals with a powered up test light.

I ALWAYS tell them to use a Multi-Meter to test the stator in the distributor and a multi-meter to test module to stator wiring with...
------------------------------------------------
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Unread 06-07-2010, 07:13 AM   #15
JeepHammer
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Quote:
Originally Posted by Ken4444 View Post
Based on the diagram in this similarly named thread...

http://www.jeepforum.com/forum/f8/25...6/#post5552499

...the Ignition Module gets its ground from the distributor. Seems like a long way to go for a ground. What if I splice in a ground wire and ground it to the firewall? My Jeep already has some things grounded there anyhow.
Why ground to the firewall when you don't know if the firewall has a full and complete circuit back to the battery?

It's MUCH better to ground your ignition by splicing into the 'Black' wire going to the distributor.
It's a direct line to the ignition module and the entire primary side of the ignition system,
And on an I-6 engine, it's already over there by the battery and your engine 'Ground'...

Once connected to the battery directly, there is no issues with rust, loose bolts in the body panels, ect.
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