1984 FJ60 No Spark

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I noticed about a week ago that my volt meter in the dash was pinging out at 16V intermittently. It happened during a 20 minute drive for a solid 5 minutes on the interstate. Not sure what happened in the meantime (I was able to drive home, no issue), but then the truck wouldn't start the next day.

First, I checked fuel. Plenty in the bowl and getting to the carb. Check.

Next I checked my battery with my digital multimeter. It was reading 11.5, so I charged it overnight. I suspect the voltage regulator is gone on my alternator, so ordered a replacement alternator/reg combo, but got the volts up to 13.5 after an overnight charge. Still won't start.

Next I checked to see if I was getting a spark off of the ingniter/coil assembly by disconnecting the distributor/plug wire from the dizzy and attaching directly to a plug. No spark when my wife turns the motor over.

I also checked the fusible link at the battery, all three points have continuity.

I then checked the coil by the touch and go method described here: Testing the ignition coil - https://forum.ih8mud.com/threads/testing-the-ignition-coil.196883/ . Coil works/I got a spark when its disconnected from the igniter.

So I think I'm down to the ignitor, but I can't be sure because the igniter also has a 2 prong female plug that goes to the base of the distributor. I can't figure out how that wiring works, but saw somewhere that the resistance across those plugs is supposed to be <5 ohms. I measured 156 ohms when I attached my digital multimeter to both prongs.

So is it the igniter? or the distributor? or something else? Any help is greatly appreciated.
 

OSS

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If the engine starter can crank over the engine- then the battery isn’t the problem.
The 2nd set of wires from the igniter are the signal wires it receives from the distributor.
 
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If the engine starter can crank over the engine- then the battery isn’t the problem.
The 2nd set of wires from the igniter are the signal wires it receives from the distributor.
I thought that I might need minimum of 12V to get the coil to function, but you're totally right, the battery is not the issue. I'm just not sure where to go next, as I can't find a way to test the igniter. If I've got to buy one, I've got to buy one. I just want to make sure there's not something else I'm missing.
 

g-man

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When my igniter died...there was no spark at the coil to dizzy wire. My truck didn't have a spike in voltage like you describe. You can test it per the 80 2f motor FSM, but it sounds like you've narrowed it down to the igniter. I opted for a GM module and a resistor and made my own "igniter". Prices for used original igniters are high, and you're getting a 35 year old solid state circuitry part that can fail at anytime.

Here's a link to the igniter repair that I found in the FAQs.


Here is a link to the resource page where you can download the 2f engine repair manual

 
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g-man

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I measured 156 ohms when I attached my digital multimeter to both prongs.
If you measured the ohms on the dizzy side of the plug...ie inside the dizzy while turning the motor ...this would be an accurate measurement of the signal generator. Meaning the signal generator is working inside the dizzy to send signal to the igniter.
 

g-man

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Next I checked my battery with my digital multimeter. It was reading 11.5, so I charged it overnight. I suspect the voltage regulator is gone on my alternator, so ordered a replacement alternator/reg combo, but got the volts up to 13.5 after an overnight charge. Still won't start.
With a spike in the voltage to 16v I would also suspect my VR was going and replace it. If your battery volts are over 15 while running the motor your VR could be the problem. They should be 14.0 to 14.8 at 2k rpms. You can test this at the battery terminals. There are tests for the IC voltage regulator in the 80 2f motor FSM under Charging sect. 9
 

g-man

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So I think I'm down to the ignitor, but I can't be sure because the igniter also has a 2 prong female plug that goes to the base of the distributor. I can't figure out how that wiring works, but saw somewhere that the resistance across those plugs is supposed to be <5 ohms. I measured 156 ohms when I attached my digital multimeter to both prongs.
The resistance is supposed to be less than 5 ohms while you have your voltage meter/multi tester leads on the coil and igniter body while touching the plug (pink and white wires on the ignitor side of the plug) to a AA battery for no more than 5 seconds. shown here:

1669126759803.png


I did this with 2 people, one touches the battery while the other works the voltage meter. Again this should be done quickly. mine failed this test.
 
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The resistance is supposed to be less than 5 ohms while you have your voltage meter/multi tester leads on the coil and igniter body while touching the plug (pink and white wires) to a AA battery for no more than 5 seconds. shown here:

View attachment 3174956

I did this with 2 people, one touches the battery while the other works the voltage meter. Again this should be done quickly. mine failed this test.
Thank you so much. This has been tremendously helpful. I’ll perform this test today and report back.
 
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Just finished the test. I passed 1-3, 12V both times. Test 4 read out no voltage/0V. Looks like I’ll be building a new one according to the instructions you listed above. Thank you.
 
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G-man and OSS, thank you. Truck is running and driving again without issue. I found a local electronic repair shop that was willing to sell me a resistor. I didn’t think those places existed anymore.

Anyway, y’all got me going again in time to grab the Christmas tree this weekend, and made 3-5 banana job more like a 2 banana job. Thank you, truly.
 

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