Losing Spark from Coil


hotrod27

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1988 Ranger 4WD with a 2.9 V6 = This has been an ongoing problem for several months. It first started by quitting running down the road. I got it home and wasn't getting fire. The next morning it started and ran fine. Drove it about 200 miles and the same thing. I have replaced the entire distributor including the ICM, Electronic pick up, cap, and rotor. I just replaced the coil tonight. No fire at first then it started. Now when it is running the coil will intermittently lose fire for a split second and then take off again. I drove it about 20 miles and other than bucking every now and again it runs fine. Thinking about running a hot wire straight to the coil from the battery; just to see if that makes it straighten up. Thoughts???
 


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adsm08

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Find the red/green wire that has key-on power at the TFI. I'd tap a light bulb into that and mount it in the cab, and watch to see if it dies during these events.

That wire has a splice that feeds it power from both the start and run posts on the ignition switch. I've had issues with that splice before, which caused me many many headaches and no-starts.
 

hotrod27

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Find the red/green wire that has key-on power at the TFI. I'd tap a light bulb into that and mount it in the cab, and watch to see if it dies during these events.

That wire has a splice that feeds it power from both the start and run posts on the ignition switch. I've had issues with that splice before, which caused me many many headaches and no-starts.
On this truck the red wire is on the positive side and it stays constant. The green wire which is on the negative side does go out when the coil does. Both are hot when the key is on? Is that correct?
 

adsm08

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1) I'm talking about the TFI ignition module on the distributor, not the coil

2) The green is a switched ground. With the key on and the engine not running you will see voltage on the green wire because it isn't grounded until the engine is cranking. With the engine running the voltage will drop across the coil, with the ground open the open ground is the largest load in the circuit, and so no voltage drops across the coil, and will be visible to a meter or a test light at the ground side.
 

hotrod27

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Checked it tonight and it does go off when the coil does. Now the $64,000 question; how do you fix it?
 

hotrod27

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1) I'm talking about the TFI ignition module on the distributor, not the coil

2) The green is a switched ground. With the key on and the engine not running you will see voltage on the green wire because it isn't grounded until the engine is cranking. With the engine running the voltage will drop across the coil, with the ground open the open ground is the largest load in the circuit, and so no voltage drops across the coil, and will be visible to a meter or a test light at the ground side.
adsm08
Checked it tonight and it does go off when the coil does. Now the $64,000 question; how do you fix it?
 

adsm08

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Time to start digging around. That wire powers the EEC relay, the coil, and the TFI, among other things.

The splice where it splits apart is listed in the EVTM as "Near air charge temp takeoff". If you look on the fender apron on the driver's side, there are a series of connectors clipped there just after it comes out of the firewall. C102 SHOULD be the farthest forward, clipped in by itself. The splice should be downstream of that connector. If I were you I'd find that splice and take a look at it. It is the most likely place to find your issue.
 

hotrod27

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Time to start digging around. That wire powers the EEC relay, the coil, and the TFI, among other things.

The splice where it splits apart is listed in the EVTM as "Near air charge temp takeoff". If you look on the fender apron on the driver's side, there are a series of connectors clipped there just after it comes out of the firewall. C102 SHOULD be the farthest forward, clipped in by itself. The splice should be downstream of that connector. If I were you I'd find that splice and take a look at it. It is the most likely place to find your issue.
Thank you. Will post when I find the issue
 

hotrod27

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Time to start digging around. That wire powers the EEC relay, the coil, and the TFI, among other things.

The splice where it splits apart is listed in the EVTM as "Near air charge temp takeoff". If you look on the fender apron on the driver's side, there are a series of connectors clipped there just after it comes out of the firewall. C102 SHOULD be the farthest forward, clipped in by itself. The splice should be downstream of that connector. If I were you I'd find that splice and take a look at it. It is the most likely place to find your issue.
Ok I got it wrong. The red wire with green stripe stays constant. It is the green wire with the yellow stripe that goes out when the coil does. I did find a green wire with a white stripe that was broken; have not fixed that yet. Haven't been able to go far enough back to hit good wire; when I try to strip it, it just breaks off. Haven't figured out what it does yet. Any more ideas?
 


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