Losing spark

[jimjumper]

Back to where I was before I jammed the over-run coupler. Ran the 8N, original 6V Front mount for about an hour yesterday with out problems. Thought I finally had the bugs worked out. Ran it today, starting hearing a little missing and by the time I got it home had a definite miss. Shut it off, checked fuel, plenty fuel from the carb. Checked spark. No spark at the first 3 plugs but got a bit of orange at the last plug and it actually started but was missing. Checked battery with a battery tester. Got good indication both no load and load. Multimeter read 6.2v without it running. No drop when running. It may have been starting a little easier as it cooled but could be my imagination. Previously, it was doing the same thing and I removed the new coil and put the old one back in which worked till now (approx. 2 hrs run time) and is why I thought I might have figured out the problem. Is it possible I have 2 weak/bad coils? I find that difficult to wrap my head around but with the quality of the other parts I've replaced, maybe not. All the parts are from TSC so I am getting suspicious...Any thoughts? Should I get another coil and try that? It just occurred to me that I should check the voltage to the coil first but if the schematic I have is correct the coil voltage comes from the resistor block after passing thru the ammeter and ignition switch. So, if I had low battery voltage it shouldn't crank or get an ammeter indication? I am getting both of those. I'll check the voltage to the coil but if it isn't getting 6 volts or enough amperage (should I disconnect the coil wire and check the amperage in series?) where should I start to look for voltage loss? For info, the generator was replaced with a new generator and a cutout vice a VR. It only had one wire to connect and the guy was very specific as to how. I doubt even I could screw it up!
Added Info: After cooling about 90 minutes I started it and it fired right up and ran great! Spark checker was still only orange but it was that way on all cylinders. I'll work on it Sunday and check the voltage.

 

[EdGooding]

Your symptoms would typically indicate a bad coil. I have a TSC near me but I buy my ignition parts from my local Napa auto parts place and have had good luck with them. Does your wiring look like this:

 

[D&D]

Have you checked your firing order (1,2,4,3), plug wires, cap and rotor, points and condenser?

 

[John0829]

Your description is typical of a bad coil. I would recommend getting a coil from NAPA, the TSC coils are not of the best quality. Be sure to check the resistor is also in good shape, the front coils are VERY sensitive about the voltage.

 

[D&D]

easy coil test?

 

[jimjumper]

Have you checked your firing order (1,2,4,3), plug wires, cap and rotor, points and condenser?

More times than I can count. And that diagram is not what I have now that it has a generator /cutout installed. Although its pretty close, there is no wire to the VR tab since there is no VR, and the ammeter is electrical vice induction? so it has 2 wires. Haven't had a chance to do anything yet this weekend. Skydiving today and a coin collecting show tomorrow. But I'll have a labeled photo Monday. Wiring looks correct, still leaning towards a weak coil.

 

[D&D]

More times than I can count. And that diagram is not what I have now that it has a generator /cutout installed.

gotcha, good luck

 

[jimjumper]

Back at again. Installed the new coil. Started good, sounded good. After about 20 minutes, I could here it occasionally missing and another 5 minutes it was definitely missing and starting to run a bit rough. Shut it off, checked spark and it barely had spark. I jumped the resistor so as to get more spark and it started. I disconnected the jumper since I didn't want to damage the points or the coil and limped it back. It was still running rough when I parked it. I started it after about 30 minutes of cooling and it ran better but was still missing a bit. Checked voltage at the coil, 6V with the key off, 2.5-3 with the key on and points closed. Checked voltage (while running) across the cut-out and it was 6.5-6.7? Verified the wiring is exactly like E Goodings pic above. Resistor reads .9? Totally confused.

 

[EdGooding]

Do you have another resistor (maybe white, ceramic, rectangle in shape) in the coil wire from your ballast resistor attached to your dash panel to your coil?

 

[jimjumper]

No, not that I've seen. Isn't that for a 12V system? Unless its in the cutout box itself.

 

[EdGooding]

No, not that I've seen. Isn't that for a 12V system? Unless its in the cutout box itself.

Yes, you would only need the extra resistor if you converted to 12v and kept your 6v coil installed. It would not be in your cutout, only the wire to your coil. Your cutout is irrelevant here. It is part of your charging circuit and your problem is in your ignition circuit. If your battery is being charged with the engine running, then you can discount the cutout and generator as part of your issue.

Do you know how old the ballast resistor is on your 8N? Perhaps that is malfunctioning and messing the voltage up enough to impact your coil? You could take a voltage reading on it with your engine fully warmed up but running right, and then do it again when the engine starts running badly. Should answer the question about your ballast resistor being bad. If you need a new resistor, it is $8 from Just 8Ns: 9N12250-9N12250 Years:1939-50 Resistor Only (No Mounting Blo or you can get the full unit with the mounting block for $22.

 

[jimjumper]

How can I tell for sure that the generator is charging? And is it possible that the battery itself has a bad cell? I'm starting to run out of parts to replace! I have a new resistor. I'll put it in and try.

 

[SPYDERLK]

How can I tell for sure that the generator is charging? And is it possible that the battery itself has a bad cell? I'm starting to run out of parts to replace! I have a new resistor. I'll put it in and try.

Have you replaced the condenser?

 

[jimjumper]

Yes. The tractor had been sitting when I got it. Replaced condenser, coil, points, ignition switch, battery. That got it to turn over. Replaced gas tank, fuel line, and screens. that got gas to the carburetor. Replaced the carb and spark plugs. Charged battery, got it to start and run. After about 2 hours running started popping and missing. I am still at the no spark step of getting it to run right. I've also replaced the flat tire and the leaking radiator, plus the generator, cutout, starter relay and starter pinion gear.. Like I mentioned, not many external parts left.

 

[EdGooding]

How can I tell for sure that the generator is charging? And is it possible that the battery itself has a bad cell? I'm starting to run out of parts to replace! I have a new resistor. I'll put it in and try.

Attach your voltmeter to your battery terminals. With the engine off, it should show around 6.2 volts. With the engine running, it should show a reading of around 7.2 or a little more.

If your battery has a bad cell, it is likely that your 8N would not even start. But, you can load test it to verify it is working. You can take your battery to about any auto parts store and they will load test it for you. If you want to be able to check that yourself, you can pick up a 6/12v load tester from Harbor Freight for about $20.

https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html?utm_source=bing&utm_medium=cpc&utm_campaign=425671834&campaignid=425671834&utm_content=1159985793876517&adsetid=1159985793876517&product=61747&store=741&msclkid=86651d4f4a291e041d537be969680c3b

 

[jimjumper]

Yep, already have one of those and it indicates the battery is good. I don't show that much when its running, about 6.5-7 volts but that should certainly be enough to power the coil. I'll replace the resistor block this morning and see what happens. i'm kinda clutching at straws here now.

 

[SPYDERLK]

Yes. The tractor had been sitting when I got it. Replaced condenser, coil, points, ignition switch, battery. That got it to turn over. Replaced gas tank, fuel line, and screens. that got gas to the carburetor. Replaced the carb and spark plugs. Charged battery, got it to start and run. After about 2 hours running started popping and missing. I am still at the no spark step of getting it to run right. I've also replaced the flat tire and the leaking radiator, plus the generator, cutout, starter relay and starter pinion gear.. Like I mentioned, not many external parts left.

In that case I think it is the distributor cap.

 

[jimjumper]

Cheap enough, I'll get one tomorrow. Thanks, Jim

 

[SPYDERLK]

Cheap enough, I'll get one tomorrow. Thanks, Jim

Old ones get fine internal cracks, absorb moisture. May be ok cold but warmth brings out the moisture, and sparks from the rotor start following the cracks every which way. The hint is the spitting and popping. Id get a new rotor too if you didnt already.

 

[jimjumper]

Minor problem with getting anything done today...Over 300 acres already and its only 5 miles away. Sorry if this is off-topic.