Uh Oh. All of a sudden No Spark

[JimsCJ5]

Weird right? The Jeep has been 100% reliable as far as starting for the last five years. I pulled it in to the garage to fix a few minor things and apply protectorant to the top. When I went to start it I had no spark. It cranks over fine but I can't get a spark from a spark plug lead or the coil. I get 6V or so at the coil with the key on. I pulled the ECM and while it looks old the back is intact with no indication of heat damage. I hate throwing parts at these types of issues so what can I check next? The coil is a five year old Accel Super Coil. It ohms out fine.

 

[coldair]

What voltage are you getting off the battery? 6 Volts is low

 

[Torxhead]

What voltage are you getting off the battery? 6 Volts is low

For the Motorcraft ignition 6 volts at the coil is to spec, when the vehicle is started up, it gets 12 volts.

 

[coldair]

Ok didn't know that learn things everyday

 

[mtnwhlr]

Are you still using the horse shoe clip on the coil? A very common problem.

 

[Lumpy Grits]

Are you sure, you are getting fuel?
LG

 

[Posi]

When I went to start it I had no spark. It cranks over fine but I can't get a spark from a spark plug lead or the coil. I get 6V or so at the coil with the key on. I pulled the ECM and while it looks old the back is intact with no indication of heat damage. I hate throwing parts at these types of issues so what can I check next? The coil is a five year old Accel Super Coil. It ohms out fine.

No need to throw parts at it every component can be tested.
If you follow the correct path getting an engine to run again is fairly easy to easy.
Do you have battery voltage at the + coil when you turn the key to crank?

 

[JimsCJ5]

Not using the horseshoe clip.

Getting fuel and I tried it using starting fluid too.

Key on I get 6.8V at the coil. When cranking the volts drop to 5.8V.

Thanks everyone.

 

[Posi]

Inspect the wire that runs from the starter solenoid I post and splices onto the + coil wire for a open or short.

I’ve found voltage drops at the splice in the past. If the wire and connection test good then we can move onto the ignition module.

 

[JimsCJ5]

Inspect the wire that runs from the starter solenoid I post and splices onto the + coil wire for a open or short.

I’ve found voltage drops at the splice in the past. If the wire and connection test good then we can move onto the ignition module.

I checked the splice (gawdawful BTW) and I am getting the same voltage as the I post with the key on.

 

[Torxhead]

You could have fried the fusible links. There are two of them coming off the battery side of the starter solenoid. One goes to the ignition switch, horn, light switch and the other goes to the alternator, the wires are both red.

 

[JimsCJ5]

My harness is hacked up and there are no fusible links left. There is a solid red wire going to the alternator and one which goes into the back of the fuse panel which is spliced for a wire that goes to the ECM. Not sure if it matters but the lights work.
One thing I was concerned about is the back of the fuse panel being a mess.

 

[Posi]

I just went back and read that your not getting spark at the end of the coil lead, if that's correct that rules out a few components.
Is your battery fully charged?
I would rewire/cleanup the splice I previously mentioned.
Check the voltage at the I post on the starter solenoid with key "on" and again in the "start" position.
Check the fusible links as Torx suggested.
If your not getting any spark from the coil lead the issue should be from the coil upstream.
To prove this run a 12v hot wire to the coil and it should start. An inline toggle switch is useful to shut down the engine.

 

[JimsCJ5]

Battery fully charged
Cleaned up splices
Voltage at I is 6.9 with the key on and with the starter going fluctuates from 6.9V to 10.7V.
I ran a wire from the battery to the coil + and still does not start.

 

[Lumpy Grits]

Might be worth reviewing.
Table of Contents

LG

 

[Posi]

Battery fully charged
Cleaned up splices
Voltage at I is 6.9 with the key on and with the starter going fluctuates from 6.9V to 10.7V.
I ran a wire from the battery to the coil + and still does not start.

The big question, when you put 12v to the + coil using the hot wire did you get a strong spark from the coil lead?
You should have battery voltage at the I post on crank.
When it cranks over does it spin fast or slow?
The voltage at the I post on crank should be steady Batt voltage something is going on there or upstream from that point.

Remove the wires from the starter solenoid
Check ohms at the S post to the base plate, should have between 3-5 ohms
Both large posts should be open
S post to opposite large post should be open as well.

 

[JimsCJ5]

No spark from the coil lead when jumped with 12V to the + on the coil.
I only get 6.9V with the Key on and less than 12V with the starter cranking.
Engine cranks over at the usual speed.
I'll check the solenoid tomorrow but I replaced it with a new one I had.

 

[Torxhead]

When you hit the starter there is pretty much a direct line from the battery to the coil. Although the current does go thru the starter relay coming out at the I terminal that could reduce current with a bad relay. There is a red w/white tracer wire from the I terminal on the relay to the coil, the brown resistance wire from the alternator goes into it also to power the coil after the starter goes off. There might be a fray in the wire not allowing proper voltage to the coil.

 

[Posi]

Key on I get 6.8V at the coil. When cranking the volts drop to 5.8V.

Voltage at I is 6.9 with the key on and with the starter going fluctuates from 6.9V to 10.7V.

Did the voltage change from 5.8v to 10.7 after I told you to clean the splice?
At the least there is now a 1.1v to 4.9 voltage improvement.
Yet no spark at the coil lead?
Are you getting the same voltage and fluctuation at the coil + as you do the I post while cranking?
10.7 at the coil is enough juice to start the engine.
I would suggest removing the coil and let if sit in a warm room for awhile. Once the coil is warm (around 75 degrees) test the resistance and post your finding.
If your getting 6.9 to 10.7. at the I post and 5.8v at the coil + while cranking you still have work to do on the wire from the I post to the coil +.

 

[JimsCJ5]

Did the voltage change from 5.8v to 10.7 after I told you to clean the splice?
At the least there is now a 1.1v to 4.9 voltage improvement.
Yet no spark at the coil lead?
Are you getting the same voltage and fluctuation at the coil + as you do the I post while cranking?
10.7 at the coil is enough juice to start the engine.
I would suggest removing the coil and let if sit in a warm room for awhile. Once the coil is warm (around 75 degrees) test the resistance and post your finding.
If your getting 6.9 to 10.7. at the I post and 5.8v at the coil + while cranking you still have work to do on the wire from the I post to the coil +.

No. What happens at the I post is it starts at 6.9V and as you are cranking the starter it it climbs to 10.7. I was getting some weird readings from my multimeter until I changed the batteries.
Still no spark.
I tried the coil from my Bronco with no change. Replaced the solenoid and no change.

I tested the coil and it ohmed out fine.


I went thru this diagnosis and it poined to a faulty trigger:
https://www.jeepforum.com/forum/f8/icm-coil-voltage-question-1296641/

I don't like throwing parts at a problem but I may try a new distributor pickup coil.