Ford 9N fouling out plugs

Anonymous-0

Well-known Member
Guys, I have a 9N that runs for about 30 minutes from a cold start before she starts to bog down and eventually quits. Check the plugs and they are completely fouled out. Put a clean set of plugs in and it starts right up. Go another 30 minutes and does the same thing. When you put it under a load and shortens the time it will stay running. Any ideas what may be causing the extreme fouling? I was thinking a valve timing issue or a rich carb. Any and all idea"s will be read. Thank you!
 
Are they fouled out with fuel or oil? Is it smoking? have you tried adjusting the carb or overhauled the carb?
 
To be honest it is my father-in-laws tractor and he told me it is not smoking and the plugs are covered in a black soot like substance so I am assuming oil. The carb that is on the tractor is a newer carb (less than 5 years old) I am not sure if he adjusted any of the mixture screws on the carb.
 
Black sot as in not oily looking or feel to them?? If yes then the carb maybe running to rich or the air cleaner need to be serviced. If oily then it is fouled by oil not gas but black and dry an sooty then gas fouled
 
troubled.......you have 2-problems, weak sparkies and miss-adjusted carb. You do NOT have a timing issue!!! The 1/2-hr timeframe for boggin' down is typical weaksister ignition switch. ($15, cheap)

2nd issue, carb is RICH. There are 2-adjustments for the M/S carb. Adjust the down-pointing mainjet to 2-turns and LEAVITT!!! Adjust the side-pointing idlemix for FASTEST idle, NOT SMOOTHEST idle. Understand the difference??? Adjust the behind the carb idle speed for extreamly SLOW 400-rpms. (ennythang under 500-rpms is good) Do that idlemix adjust 3-times. The last time I adjusted my eazy start 6-volt 8N, my idlemix was 1/8-turn and idle was 435-rpms on new proofmeter. Remember the side pointing idlemix is BASSACKWARDS; out fer lean, IN fer ENRICH.

BTW, recommend AutoLite 437's gapped 0.025"........Dell, yer self-appointed sparkie-meister
 
Based on what he was telling me yesterday, I believe it is gas becuase it sounds like they are dry and not oily. Sounds like they are full of carbon hen he pulls them out.
 
you may be assuming wrong.

black soot is fuel / rich.

oily black is oil fouling.


you are rich and or may have weak sparks.. which was why it may hav ebeen set rich.

air cleaner may be blocked and choking it too.. and / or choke partially engaged.

post back
 
I will defintely look at the air cleaner to make sure that is not plugged at all. Thanks for the great advice
 
Ill try again.when I bought my 640 it had a new set of Champion H10s in it.I drove it 12 miles home,ran fine.It use it was fouling plug a lot.I put in H12s and the problem was gone.I did find that prolonged idling can foul the H12s so bad that you cant move in first gear.I had to bring the rpms up slowly until the fouling cleared up.Ive tested gas fouled plugs in the shop with a Model T coil.The spark runs up the nose of the insulator in thin streams.It CANT jump the gap.The fouling keeps the spark voltage low so you think you have weak spark as the problem.Most favor the Autolite 437 plugs.The Autolite 216 has the same heat range as the Champion H10.This has been posted many times but seems to be ignored .You have to use a HOTTER plug with unleaded gas.
 
Thanks for the tip on the hotter plugs. I think along with the carburator, which seems to be running rich, we should be able to take care of this problem. Thanks again!
 

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