Fried Coil ?

[reavesga]

I am running an electronic ignition conversion on my 1974 3.0L. I have a couple of projects going on right now. The drive is off and the billows are out. replacing the billows. While I was at it I decided to replace the lifters as well. I have had one talking to me for a couple of years. Since I had to open it up I decided to replace all of the lifters. Anyway, in the process of rotating the motor to adjust the valves I started to smell something getting hot. it turned out with the drive off, when I pulled the shifter back into the neutral position the cabled did not slide and triggered the shift interrupt switch. I turned the motor over and in the middle of adjusting the valves I smelled hot and started hearing some popping. I immediatly reached up and turned the key off and realized what I had done. With the key on power is going to the coil with the electronic conversion. however since the **** switch was triggered the coil was ground, so basically it was just part of a big heater circuit. The wires were really hot and the coil was pretty dang hot. I finished adjusting the valves. Put everything back together. made sure that shift switch was not tirggered and tried to fire her up. yes I connected a hose direct to the thermostat housing for cooling, since the drive is not installed. Anyway, motor turns over but no fire. Pulled the coil wire off at the distributor and just layed it there. no popping. I mean there is nothing. the motor does not even spit or cough or anything .there is no fire. And I am guessing the reason is no spark. So the question is, did i burn out the coil? I have never heard of a coil burning out, but the ignition circuit is pretty simple so either the coil is bad or the electronic trigger on the distributor is not doing its thing. not really sure how that works. it just has a cable that goes from the distributor to the coil.

Thoughts?

 

[Scott Danforth]

you most likely burned out the electronic ignition trigger module

 

[gm280]

If you have a meter, you can easily test the coil for continuity and see if it is not toast. If it reads any resistance, it is probably okay. However if you can't read anything, time to buy a new one. JMHO

 

[reavesga]

Coil post to ground reads pretty high resistance

 

[gm280]

Coil post to ground reads pretty high resistance

That side (secondary) is supposed to read high. That side has the most windings. What about the other side (primary)?

 

[reavesga]

The plug that has the tacb and power on it reads as follows

Pin to pin 0.4 ohms. Same reading I get with just the probes.
+pin to ground 8.4Mohms
Coil spark plug wire stud to ground also about 8M ohms

Now I unplug the trigger wire from the distributor.

Coil spark plug wire stud to ground reads open circuit

Any thoughts?

 

[gm280]

The plug that has the tacb and power on it reads as follows

Pin to pin 0.4 ohms. Same reading I get with just the probes.
+pin to ground 8.4Mohms
Coil spark plug wire stud to ground also about 8M ohms

Now I unplug the trigger wire from the distributor.

Coil spark plug wire stud to ground reads open circuit

Any thoughts?

Sounds like the coil is open with the tower spark plug terminal to ground being open. But not being there and testing things myself, that is merely a wild guess from your readings. JMHO

 

[reavesga]

Replaced the coil and now I have spark. not sure what was wrong with the coil as the new one measured the same as the old one on all of the same measurements. However, replaced the coil and now I have spark. Motor still did not run though, but I got a couple backfires. So I decided to replace the module in the distributor. Same results. I think I have since traced that problem to valves as i changed the lifters at the same time and I am not sure that is working right now. Will changing the module in the distributor change the motor's timing. I would not think so.

 

[gm280]

Replaced the coil and now I have spark. not sure what was wrong with the coil as the new one measured the same as the old one on all of the same measurements. However, replaced the coil and now I have spark. Motor still did not run though, but I got a couple backfires. So I decided to replace the module in the distributor. Same results. I think I have since traced that problem to valves as i changed the lifters at the same time and I am not sure that is working right now. Will changing the module in the distributor change the motor's timing. I would not think so.

If you are getting the exact same reading on the new coil with the old coil, then don't throw your old coil away just yet. It could be good and had some bad connections. But again not being there to trouble shoot your engine, that is merely wild guesses. It does sound like you have some ignition problems yet to find as well. JMHO

 

[reavesga]

Fresh eyes this morning and I realized that I swapped 3&4 plug wires on reassembly. Valves were also adjusted too far down. So rough readjustment on the valves and unswapped 3&4 it should fire up I hope. Will post the results once I get it done. I did swap the old coil back in to the system. No spark. it does read about 1.5K ohms less than the new coil. New coil reads 9,5Kohms, old coil about 8Kohms. Guess that is making a difference somehow. Figure the ignition module swap was probably not required. The no start was probably due to the valves bein way off. Once I get it running again I will post a summary so that another reader can see the fun I have had, mostly caused by myself and a stupid oops.

 

[reavesga]

Update: With the distributor hooked up right and the valves readjusted she fired right up. Bottom line, the coil was fried.

 

[fishrdan]

Have you broken in the lifters? 15-25 minutes at 1500-2500RPM? Swapping in a new set of lifters requires break-in, just like installing a new cam.

 

[reavesga]

Is it ok to run 2500 rpm turning just the fly wheel? Any special oil? Or just run it?

 

[fishrdan]

No problem with the drive disconnected, just make sure you have plenty of water going to the engine. Fire it up and take it to 1500-2500 RPM.

A high zinc content oil like Rotella should be used with a flat tappet cam, just not for break-in.

Noticed your other thread saying #7 push rod was spinning, they should all do that, it's the reason for breaking in the cam/lifters, establish a wear pattern so the lifters spin.

 

[salty3rd]

Update: With the distributor hooked up right and the valves readjusted she fired right up. Bottom line, the coil was fried.

Nice work, I have talked to people that refuse to believe coils can fail. But they absolutely do, I've have changed a couple just on my own boats. Good luck