8N shuts off after running for a while

[JerryLook]

Here are the details. It’s a 1950 8N with front mount distributor. We use it for mowing a small field. After running for about an hour it will just shut off. If you let it sit and cool down for an hour or two it will run for another hour.

It’s only used a handful of times a year.

It’s been happening for a while. Outside temp doesn’t matter. It happened today and it was only 65 out.

Last year someone told me it could be a bad coil when it gets hot. I replaced it with one from this site. It still dies after an hour.

The tractor is still 6v

Oil pressure is a solid 30psi, and it doesn’t seem like it’s overheating. It’s not bogging down or being run too hard. When it dies it’s like someone just turns off the key.

Any ideas?

 

[HarryVanderpool]

You are going to have to trace it out.
Throw an el-cheapo VOM in the tool box.
As soon as it konks out, check for voltage at the coil.
Definingly sounds heat related.

 

[Mad Farmer]

When my 9N started that it was the coil. Problem got worse and worse. Finally one time would not restart at all, on a Sunday.

Only place still open who had a coil was TSC. Glad I checked the box before I went to checkout, what a POS!!! Whole top of coil was so loose you could wiggle it.

Went to NAPA the next day and ordered an Echlin coil, 2X price of TSC POS. Much better quality and still running years later.

 

[6 SLY PLACE]

It also could be the key switch you would have to check and see if you have power to the coil when it dies on you

 

[JerryLook]

I’m not sure which brand coils they sell on this site. I got the “non script” version.

My father replaced the key switch on the tractor probably ten years ago. I’m not sure what he used for that. I was reading another thread last night and saw that mentioned as a possible culprit for my issues.

I agree it’s something electrical that’s heating up and going open etc

 

[Eman85]

70+ yo tractor, we can guess you to death on what's possibly wrong. You need a pint jar a spark tester and a test light at the least for some diagnosis. First up is the dreaded fuel flow test, most would rather suffer a slow death than perform it. Shut the fuel and remove the plug from the bottom of the carb and let it drain. Place the jar under the carb and open the fuel and time how long to fill a pint jar. Do a spark test with a spark tester set at 1/4" gap. If or when the tractor quits check for spark immediately and also check for power coming from the ignition switch to the coil.

 

[Cliff (VA)]

Here are the details. It’s a 1950 8N with front mount distributor. We use it for mowing a small field. After running for about an hour it will just shut off. If you let it sit and cool down for an hour or two it will run for another hour.

It’s only used a handful of times a year.

It’s been happening for a while. Outside temp doesn’t matter. It happened today and it was only 65 out.

Last year someone told me it could be a bad coil when it gets hot. I replaced it with one from this site. It still dies after an hour.

The tractor is still 6v

Oil pressure is a solid 30psi, and it doesn’t seem like it’s overheating. It’s not bogging down or being run too hard. When it dies it’s like someone just turns off the key.

Any ideas?

The late great sparkie-meister Dell used to have a list of all the things that made the tractor quit running and the time it took to shut off.

Dell's words on why the tractor quits running

My best guess is that you do not have the correct resistance in line with your coil and you are over heating the coil. You may have already damaged your new coil. If you search the archives you can find some more information on this.

RIP Dell. We miss you.

Cliff(VA) now (NC)

 

[Cliff (VA)]

The late great sparkie-meister Dell used to have a list of all the things that made the tractor quit running and the time it took to shut off.

Dell's words on why the tractor quits running

My best guess is that you do not have the correct resistance in line with your coil and you are over heating the coil. You may have already damaged your new coil. If you search the archives you can find some more information on this.

RIP Dell. We miss you.

Cliff(VA) now (NC)

Here is a good thread on coil resistance and external resistors.

A discussion on coil resistance

You need the ballast resistor also. Very important!

Ballast Resistor

Cliff(VA) now (NC)

 

[old]

Here are the details. It’s a 1950 8N with front mount distributor. We use it for mowing a small field. After running for about an hour it will just shut off. If you let it sit and cool down for an hour or two it will run for another hour.

It’s only used a handful of times a year.

It’s been happening for a while. Outside temp doesn’t matter. It happened today and it was only 65 out.

Last year someone told me it could be a bad coil when it gets hot. I replaced it with one from this site. It still dies after an hour.

The tractor is still 6v

Oil pressure is a solid 30psi, and it doesn’t seem like it’s overheating. It’s not bogging down or being run too hard. When it dies it’s like someone just turns off the key.

Any ideas?

When it dies check that you still have a good blue/white spark that will jump a 1/4 inch gap at all 4 plugs. No spark or weak spark can be a bad coil or a bad ignition switch or even a bad resister. Hot wire it if no spark and see if it runs. If it does the coil is good but could be a bad switch

 

[JerryLook]

I appreciate the help guys. I’ll take some readings with the meter when I first start it to get a baseline. Then as soon as it quits I’ll run through the list of things to check real quick.

I have not done anything with the ballast resistor. I should check that.

 

[JJay48]

I would also guess it has to do with the resistance to the coil although im no wiring expert that is where I would start and I would check the ohms through the resistor when it quits and check the ohms on the coil. Also check to make sure your still getting the expected voltage. Not much to the wiring so I would guess an issue with the ballast resistor or coil/condensor/points.

 

[Mad Farmer]

I carry 3 jumper wires w/alligator clips in the tool box. A short one I can jumper the key switch/resistor, a longer one I can reach the coil from the battery with (and most other electrics). And another short one heavier gauge wire, for when a generator cutout , cuts out.