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Ford 9N Spark Plugs arcing at the boots

W

wjfletcher

New User
Hello. I am new to this forum and I am looking for some help in solving a problem I am having with my 9N. I have replaced all of the spark plug wires, spark plugs (AL437), as well as rebuild the distributor. The tractor cranks and runs but sometimes the plugs arc at the boot connections. When this happens, the tractor misses and does not run worth a darn but it clears up and runs fine. I was thinking that cleaning the carburetor may help since that is the only thing I have not done yet. Any suggestions?
 
I failed to mention that the tractor had AL216 plugs in it when I got it. I read where the AL437 plugs are better and hotter. Should I go back to the AL216 plugs?
 
Thanks Gene for the reply. Yes. I did gap the plugs after the initial plug install (I did not gap then). I set the gap to .025 and it seemed to help. I also added dielectric grease to the boots. The tractor will still arc outside the boots occasionally. As of this reply, I have the carb off and cleaning now.
 
That is a very unusual event for an old tractor! Usually that happens with a high power, high tech electronic ignition system.

Did this start after replacing the plugs, or wires, or coil?

Arcing to ground is usually caused by a high resistance path from the coil to the plugs. The voltage is looking for the easiest path to ground, and if jumping out through the boot is easier than going through the spark plug, it will do what you describe.

Here's what comes to mind:

Defective plugs, the internal connection was not made, something left out in the assembly process. Try a different set of plugs, old ones if you saved them.

The boots were possibly made from the wrong rubber compound and are highly conductive. Try pulling the boots up the wire away from the engine.

The tractor is somehow getting wet, dew, condensation. Especially if it runs good after warming up.

Has this been converted to 12 volt? Was the coil changed or a resistor added? If not the coil will make an extra hot spark for a while until the points burn or the coil burns out. But even then, it should not try to jump outside the wires. Strange indeed!
 
I do not remember the arcing before changing the plugs. Yes. The tractor has been converted to 12 volt. I am thinking I need to get a set of the AL216 plugs and try them. The 216's are what was running in the tractor when I got it. According to what I have read, they do not run as hot as the 437's. I did clean the carb and now the arcing seems to be coming from the #2 plug every now and then.
 
(quoted from post at 11:00:54 08/02/23) I do not remember the arcing before changing the plugs. Yes. The tractor has been converted to 12 volt. I am thinking I need to get a set of the AL216 plugs and try them. The 216's are what was running in the tractor when I got it. According to what I have read, they do not run as hot as the 437's. I did clean the carb and now the arcing seems to be coming from the #2 plug every now and then.
Click to expand...



This post was edited by wjfletcher on 08/02/2023 at 11:20 am.
 
Hotter plugs are to fix/patch a problem. Non resistor plugs and solid core wires.
 
What is by them boots that the spark is jumping to?them old tractors did not even have boots. Sure got me curious. A carburetor has nothing to do plug arching. Put the proper plugs back in it I would say. Something wrong there if it wont jump the plug gap.
 
I'm thinking you have a defective plug, maybe a cracked insulator, bad connection inside the plug.

The difference in the plugs is the heat range. If the engine is tired and burning oil, or it never gets
run under load, then the hotter plug will help with preventing fouling.

If it is healthy and used as a working tractor, the colder, original plugs are the better choice.

Neither will contribute to the arcing.
 

Remove the boots (typically they come of easily if you work some silicone lube spray under them).

If arcing continues the spark plug insulators are cracked or have a deposit of some sort of conductive material on them
 
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