6 volt coil question

[wolc123]

Would a 1951 Ford 8n and a 1956 Farmall Cub both use the same part number NAPA coil ?

 

[JJT]

I've successfully swapped a 6 volt coil between a model A car and a 9N tractor. I'd give it a try.

 

[Roadworthy]

If it fits in the mount try it, it will probably work fine. Both are pretty simple tractors.

 

[LouNY]

I believe that both of those would have been 6 volt positive ground systems, so yes the same coil should work in either.

 

[wolc123]

If it fits in the mount try it, it will probably work fine. Both are pretty simple tractors.

I bought one for my 8n last fall, at a NAPA way out in the country. They probably sell more for tractors than they do for cars at that store. The guy at the counter didn’t even look at the computer to find it.

I went to the closest one back home today, and they only carried one 6 volt coil. It’s the same part number as the one I got at the other store. Now I have two in my parts cabinet at home.

They both look like they will fit the 8n, no problem, so worst case, I’ll have a spare for that. It might be a challenge fitting one of them on the Cub though. The original looks a little smaller, it’s mounted sideways, and it looks like at least one of the wires connects at the opposite end.

If it warms up a bit this weekend, I might try to get one of them swapped out on the Cub. I’m not sure the coil is the problem but maybe I can rig up some jumper wires, if need be, and at least prove that is the issue, before forking over big bucks for a “proper” replacement.

My previous Cub had been very heavily modified over the years and I would like to keep this one as original as possible. The hood on my old one had been torched up to make room for a big 12 volt alternator. If I can get the Cub fired up on the $34 NAPA coil, maybe I’ll spring up to $70 on a properly fitting replacement.

I mostly only use that Cub for snowplowing in the winter and the Ford for ground plowing in the spring. Lake Erie is pretty much froze over now so I don’t think we’ll be getting any more “lake effect” snow this winter. I may need the Ford before I really need the Farmall again.

I’ll tell you one thing about these red and blue (actually grey and red in the case of mine) tractors, owning them sure makes me appreciate the green ones.

That little Farmall Cub sure is fun to plow snow with though, as is the Ford 8n for plowing ground. Keeping them running is a real challenge, compared to the John Deere’s that I’ve been fortunate enough to own or operate.

 

[ultrarunner]

I run the cub with no battery and never paid much attention as it’s crank start and I just assume magneto ignition?

 

[ruffdog]

I have seen more problems with the cheap import points and condensers than with coils.

 

[wolc123]

I run the cub with no battery and never paid much attention as it’s crank start and I just assume magneto ignition?

Mine cranks over real good but clearly there is no spark. No magneto ignition either (it has a coil connected to a distributer cap).

When it quit, it was just like somebody turned off a switch. The coil looks like it would be about the easiest thing to check as my first “parts swap”.

My old Allis Chalmers C had magneto ignition and no battery on it. I always started that one with a crank handle. It started real good over a narrow temperature range. Was always firm “no go” if it was too hot or too cold though. Once again, orange was another color that gave me appreciation for green.

 

[ultrarunner]

Wish we were closer as I have access to a coil tester.

I've had weak coils found through using a scope... Spark was fine for ideal but no good under load.

Also had bad switch, lose wire or ground inside distributor...

If timing ok and it doesn't try to run with starting fluid or propane it points to electrical...

 

[DJ54]

Did you check for voltage from the switch to coil first before buying a new coil..??

 

[wolc123]

Did you check for voltage from the switch to coil first before buying a new coil..??

I did on my Ford, but not yet on the Farmall. I will before I try one on that. Worse case, I got another spare $ 34 NAPA, made in China, coil for the Ford.

If the coil is the problem, but I can’t make that big China-made NAPA one fit the Farmall, then that will be the case anyhow.

 

[LouNY]

Lots of places to get a 6 volt coil for less then that;

 

[ruffdog]

Another thing....you don't need to keep cranking the engine over to test the ignition system. The correct side of the coil should have power and the points need the make/break the ground on the other side of the coil. Open and close the points with your thumbnail and see if you have spark from the high tension lead from the coil. No spark? Check the points with a ohm meter to see if they are making/breaking the connection.

 

[wolc123]

Lots of places to get a 6 volt coil for less then that;
View attachment 2410146

“Less than” is not always the ticket. This will be the third one on my 1951 Ford 8n. I’ve heard that the NAPA ones are supposed to last the longest. The last one that I got for it was from TSC. I see that the new ones from NAPA are made in China. There seems to be quite a variation in product quality coming out of that country.

 

[LouNY]

Strange that you are having that much issue with coils.

 

[wolc123]

Strange that you are having that much issue with coils.

I’m not 100 % certain that I am. The original from my Ford 8n might still be good. I’ve still got it in my parts cabinet, along with the two new NAPA Chinese ones. It was just one of many parts that we changed out the last time it had acted up. It didn’t run right again that time, until I changed out the whole distributer.

My cousin is a better mechanic than I am and he thinks that the coil is the problem with that Ford tractor right now. It is a cheaper coil from TSC that I had used on the initial replacement.

I’m also not sure that the coil is the current problem with the Farmall Cub. It just seemed like it might be based on the way it quit running, and it is about the easiest part to swap out first. Hopefully, I’ll find time to get back on that project, over the next few weeks. These red and grey tractors sure are good for killing time.

My John Deere is running great as always, so there’s been no real need to work on them, plus it’s been too cold out in the barn. I’ve got a bunch of books to read, inside the house by the wood stove.

 

[ruffdog]

Is the tractor a positive ground? Is the coil polarity correct?

 

[wolc123]

Is the tractor a positive ground? Is the coil polarity correct?

Yes positive ground. That’s not the issue. The tractor was running good and stopped suddenly, as if someone had turned off a switch. It probably would not have started and ran if the coil polarity was wrong.

I did have it running with the leads reversed on a new 6 volt battery for a couple weeks earlier last fall though, and it didn’t seem to do it any harm. Maybe it did damage the coil or some other part though. The dash amp gage showed discharge when running when the battery was in backwards with the leads reversed.

I switched it back the right way (positive ground) and all was well the first (5) times I plowed with it this winter. The “switched off” loss of spark failure happened 15 minutes of run time into my 6th plowing of the winter, one week ago.

 

[DJ54]

Sounds like more of an electrical connection problem being that it died that quick. A simple test light will help you diagnose that problem. Put the clip end on a good ground, battery is best if the lead is long enough. Put the tester end on the input side of coil from switch, it should light up with switch in the run position. If you show voltage there, with tractor in neutral, put tester on the output side, and roll the engine over with the starter. Test light should flash. If it flashes, put the tester on the connection point on the distributor and turn over, you should see it flash. Doing that, you know your wiring is good to there. Remove the distributor cap and check the connection inside, you should still see if flashing when turning over. I have seen those Bakelite insulators crack, and short out on the distributor case.

If you have voltage to there, turn the switch off for a moment. Rotate engine until points touch. Turn switch on, and break/separate the points manually with a small screwdriver, you should see a small spark when the points separate. If you see a spark, look closely at the points, especially the rub block. The lesser expensive contact points set's rub blocks can wear, bend, or completely come off. The one on my TO35 Ferguson was completely gone. Friends of mine literally gave me this tractor and several attachments just to get it out of their yard. They got frustrated after piddling with it, and just wanted it gone. A new points & condenser kit, new plugs, purged/cleaned the fuel system, and a good carb cleaning, and it fired right up. A few more issues to deal with when I get time but should be a good useable tractor once time allows to look into those.

If you have voltage to inside the distributor, I'd have to guess it's the condenser. Some simple diagnostics like this can save you a lot of money just throwing parts at it.

 

[wolc123]

Sounds like more of an electrical connection problem being that it died that quick. A simple test light will help you diagnose that problem. Put the clip end on a good ground, battery is best if the lead is long enough. Put the tester end on the input side of coil from switch, it should light up with switch in the run position. If you show voltage there, with tractor in neutral, put tester on the output side, and roll the engine over with the starter. Test light should flash. If it flashes, put the tester on the connection point on the distributor and turn over, you should see it flash. Doing that, you know your wiring is good to there. Remove the distributor cap and check the connection inside, you should still see if flashing when turning over. I have seen those Bakelite insulators crack, and short out on the distributor case.

If you have voltage to there, turn the switch off for a moment. Rotate engine until points touch. Turn switch on, and break/separate the points manually with a small screwdriver, you should see a small spark when the points separate. If you see a spark, look closely at the points, especially the rub block. The lesser expensive contact points set's rub blocks can wear, bend, or completely come off. The one on my TO35 Ferguson was completely gone. Friends of mine literally gave me this tractor and several attachments just to get it out of their yard. They got frustrated after piddling with it, and just wanted it gone. A new points & condenser kit, new plugs, purged/cleaned the fuel system, and a good carb cleaning, and it fired right up. A few more issues to deal with when I get time but should be a good useable tractor once time allows to look into those.

If you have voltage to inside the distributor, I'd have to guess it's the condenser. Some simple diagnostics like this can save you a lot of money just throwing parts at it.

I’m not sure my 12 volt test light will work at 6 volts but I do have a cheap hand held multi-meter that I can probably use for diagnosing. Thanks for the tips, I’ll refer to that list when I get back at it.

I’ve got two out of three of the tractors that I use for snow clearing working very good now, since I finished adding wheel spacers to my dad’s John Deere 770 yesterday. I spaced the rear tires out about 5/8” so the chains no longer rub on the fenders.

I just need a combination of a little free time, and warmer temperature, to get back to work on the Cub.