Help!! No Spark From Coil??

connor014 · 12-20-2008, 05:58 PM

So I am not getting a spark from my coil. I pulled the wire and put it to the negative terminal and tried turning the engine over. It wont spark until I switch it to off and then I get one or two sparks. I replaced the coil and it still does the same thing. The coil is getting around 6V but when I am turning it over it gets a little over 9V so I am not sure if that is a problem. The only thing left that goes between the battery and the coil is the solenoid. Do you think this could be causing the problem? I need to get my heep going!!

**JeepHammer** · 12-20-2008, 07:29 PM

Quote:

Originally Posted by connor014

So I am not getting a spark from my coil. I pulled the wire and put it to the negative terminal and tried turning the engine over. It wont spark until I switch it to off and then I get one or two sparks. I replaced the coil and it still does the same thing. The coil is getting around 6V but when I am turning it over it gets a little over 9V so I am not sure if that is a problem. The only thing left that goes between the battery and the coil is the solenoid. Do you think this could be causing the problem? I need to get my heep going!!

The fact that you have a new coil, and that the coil is getting power, and you get the requisite spark when you kill the power (exactly what it should do) means you probably have a bad module.

Look for it under the washer tank on the dirivers side.

Aluminum box about 5" square, 2" thick,
Two connectors, one with 4 wires, one with two wires.
Connectors pull straight apart, retainers, no locks.
Three bolts hold it on the fender from inside the wheel well side.

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=ECH&PartNumber= TP40&Description=Ignition+Control+Module

connor014 · 12-20-2008, 07:36 PM

yeah i actually just finished looking at the wiring diagram and saw that the green wire runs to the module. when i was putting in my custom dash i had to move the module (but i never disconnected it) about 4 inches the other way to make room for some gauges. i am wondering if this damaged it somehow. also what you were saying about the spark at the end i am kind of confused. when i turn the motor over the coil should not be putting out a spark constantly to the distributor (or while testing i use the ground)? if this is true could it be something in the distributor if the coil is working properly?

connor014 · 12-20-2008, 07:41 PM

also i noticed on the coil where the red and green wires go in on the bracket there is a red wire going in then another red wire hanging off of where the other red wire goes in that has a connection on it after about 4" of wire that usually goes on the tip of a bolt type connection. it looks like this is not important from the wiring diagram since there is the red wire going in giving it power. JeepHammer thanks for the help! I found one at autozone for $35 so i will probably pick it up tomorrow and see if it does the trick.

illinicj · 12-20-2008, 08:00 PM

I imagine if you relocated a box doing work on the dash, it was the computer, not the module. The module is under the hood, on the fender, as JH mentioned. I got sick of replacing modules and wired in a GM HEI module (not distributor). They are cheaper and, in my experience, last longer.

connor014 · 12-20-2008, 08:03 PM

Ah for some reason I saw that box and remembered moving it so I thought it was the computer. I am leaving for the auto parts store now to pick it up and see if it will fix the problem. Thanks for all your help!

connor014 · 12-20-2008, 10:47 PM

so i have replaced the coil, ignition control module, and starter solenoid. now when i try to start it it just sparks once at the beginning and it no longer sparks at the end. isnt it supposed to spark repeatedly? any other ideas? the connection at the control module was a little corroded so tomorrow i am planning on cleaning and spraying out the old connections to put into the new module.

OldSailor · 12-21-2008, 02:34 AM

The wire coming out of the coil should spark six times for every two revolutions of the crank shaft, and each spark plug wire should spark once for every two revolutions of the the crankshaft.

Clean and reconnect those two connnections to the ignition control moduyle, as well as the similar conenctor to the distributor.

BTW, the voltage to the coil should be somewhat higher -- about 12 volts when cranking the engine, and 7 to 9 volts once it's running.

**JeepHammer** · 12-21-2008, 01:06 PM

Quote:

Originally Posted by connor014

yeah i actually just finished looking at the wiring diagram and saw that the green wire runs to the module. when i was putting in my custom dash i had to move the module (but i never disconnected it) about 4 inches the other way to make room for some gauges. i am wondering if this damaged it somehow. also what you were saying about the spark at the end i am kind of confused. when i turn the motor over the coil should not be putting out a spark constantly to the distributor (or while testing i use the ground)? if this is true could it be something in the distributor if the coil is working properly?

All ignitions fire when the power is switched 'Off' to the ignition coil.
The coil is magnetically saturated as the power flows through it,
Then when the power is turned 'OFF' the magnetic field collapses through the secondary windings and produces an electric discharge we call 'SPARK'.

'86, the distributor only signals the module to fire the coil.
The way to test your module is to conect a test light to the POSITIVE side of the battery,
Make sure you get a 'Bright' light when the probe touches the 'Negative' side of the battery,

Then remove the coil connector, probe the 'Green' wire terminal while cranking the engine.
---------------------------

If you get a 'Bright' light when you make contact, that is what it's supposed to do.
This means the 'Green' wire terminal, wire and path through module is intact.
If you get a 'Dim' light, you ground to the module needs some work, and is probably the reason the module failed.
---------------------------

If the test light 'Flashes' when you crank the engine, that means the distributor is signaling the module to trigger the coil,
And the module is working like it's supposed to.
--------------------------

If the test light doesn't light up at all, then you have a problem with the ground wire between coil connector and module,
The module isn't properly grounded (also a problem).
Or,
The distributor stator isn't triggering the module.
--------------------------

98% of the time, it's the module...
1% of the time, it will be the coil connector/green wire to the module.
1% of the time it will be the distributor 'Stator' (Magnetic Trigger).
----------------------------

I suggest you remove the module after your own testing and have it tested at a couple of the discount stores...
I say a 'Couple' because sometimes the kids/burnouts working there don't have a clue how to use the testing equipment.
----------------------------

Why would you have to remove a module off the drivers side fender for a dash install?

connor014 · 01-05-2009, 12:01 AM

Thanks for the good info JeepHammer. I was mistaken earlier I confused the module with the computer at first. What do you mean by "'86, the distributor only signals the module to fire the coil"? To test for the spark I was placing a small gap from the coil to the negative terminal which I thought should spark continuously, therefore I thought the problem had to be the coil or before the coil. Is this incorrect if you say the distributor signals the control module? If so it could just be the distributor then? I have been gone for the past few weeks and am returning to the heep tomorrow to try to get er going. So since I have replaced the coil, module, and starter solenoid and still only one spark from the coil when trying to start it. My thoughts now are on the wiring unless it is the distributor but I was thinking it was the coil or before since it was not sparking continuously. When turned on the on position the coil gets the correct voltage (i think around 6) and when turning over it only gets a little over 9. The haynes manual said it should be at the battery voltage so it seems to be a little low. Could it be in the ignition switch or have something to do with the resistance of the wire for when it is turning over? I remember seeing that it gets a different voltage when turning over compared to running. Any ideas?

connor014 · 01-06-2009, 08:25 PM

My manual really does not talk about diagnosiing this very well as far as wiring issues. Can anyone get me a link or the routine to check all the wiring up to the coil and for the resistant wire and module? I am not the best as far as diagnosing electrical issues...

connor014 · 01-07-2009, 02:56 PM

Ok so I bought the factory manual. Since when turning over the engine the coil only gets about 8.8 instead of the 12V it narrowed it down to either the starter solenoid (which I replaced) or the resistance wire. The resistance wire should be 1.35ohms and mine turned out to be 1.8 ohms. I am guessing I need to replace this wire. My thoughts are though the coil should be getting 12v when turning over so can I just run a wire from the battery to the coil for right when it starts then pull it off or would this damage something?

Fjguercio · 01-07-2009, 06:51 PM

Quote:

Originally Posted by connor014

I checked the resistance in the wire from the ignition switch to the coil and it was 1.8 ohms when my manual says it should be 1.35 ohms. I believe this is what is causing the coil not to fire because when it is turning over it only gets around 8.8V instead of 10V. I went to kragen and they sold me a ballest resistor I was going to wire in place of the resistance wire. When I got home I checked and it is actually around 5 ohms.

Can anyone point me in the right direction for a new resistance wire or resistor that is correct?

Here you go, I agree you should stay with 1st Thread until you get going.

I think Napa or Jeep Dealer or Ford Dealer should all carry the IGNITION RESISTANCE WIRE 1.35 OHMS. Jeep uses a Ford DuraSpark Ignition so call them and could use Late 1970's thru 1980's models.

They use the long wire because it disapates the heat better than the ballast resister and lasts a long time. The ceramic balast resistors also crack from heat cycle shock and physical shock.

Yes the RESISTANCE WIRE should be 1.35 ohms or read just a little higher from contact resistance like 1.4 maybe. So this could cause you low voltage to coil.... V=IR so when the resistance is higher the V at coil would be less

connor014 · 01-07-2009, 07:16 PM

Alright thanks I will contact them and see if I can get the replacement. I am confused though why it was still 8.8V though when cranking with a different resistance (with the 5 ohm ballast resistor). It seems like that wire controls the voltage when in the on position rather than the cranking position. I thought it was the other way around.

Fjguercio · 01-07-2009, 08:03 PM

Not sure how you put the 5ohm ballast resister into your system????
Nore do i think that is a good idea.

I am going on what you said in post #12

I had a post asking about finding and testing for the 1.35 ohm resistor. I will look at again to see if it will help you. Be right back.

Here is a link where I ask about the 1.35 ohm ignition wire
http://www.jeepforum.com/forum/f8/1978-cj7-w-weber-34dgec-runs-rich-manifold-heater-where-1-35ohm-wire-498227/

I just read your last post..... why would you put a 5 ohm resistor in a circuit that takes a 1.35 ohm resistor. Do not play like this unless you realy know what you are doing.

At this point you need to follow JeepHammer process and read the post all the way thru there is a MISTAKE in the process. Post up your results again.. Verify battery voltage, wire resistance, voltage at coil. I also suggest you read resistance of the coil also... do you still have the old stock coil???