Ford 8N ignition problem

Shayneberlo

New User
i have a Ford 8N with a 12 volt conversion. It runs great at startup then sputters, misses and eventually dies after a few minutes. It will not start back up for several hours. Ive replaced spark plugs/wires, distributor, condenser and coil. Its getting fuel and carburetor is clean. What else might be causing this problem and how do I diagnose it?
 
Most likely one of those 6 items that you pronounced all well & good isn't. Front mount distributor or side mount? Coil require a resistor or not? If yes, what resistor is being used (style & value in Ohms). Checked fuel flow out carb bowl drain plug for a pint in 2-3 minutes?
 
These tractors are pretty simple machines; it’s usually pretty easy to get them running with some basic troubleshooting steps.

There are three approaches you can take:


1. Replace every part you can until it starts or you run out of money.

2. List every possible cause of the problem and then randomly pick your favorite to check. It could be your coil. Or your ignition switch. Or about 10
other things.


3. Like diagnosing any other equipment failure, take a step-by-step approach, working from the most likely to the least likely, one system at a time.



I’ve tried all three approaches. The third one always worked for me. Sounds like you are trying option # 1.



I might not be able to tell you why your tractor isn’t running, but I can tell you how to figure it out for yourself.


You could have a spark issue.


You could have a fuel issue.


Don’t guess. Troubleshoot. Do exactly as JMOR suggested. See tip # 13 at the link below.


You need to answer 2 questions before you do anything else:


With the bolt in the carb bowl removed and the gas on, will the fuel flow fill a pint jar in less than 2 minutes?


Next, get out your adjustable gap spark checker * , open the gap to 1/4", hook it up, turn the key on and crank the engine. Does the spark jump 1/4"? Post back
with the answers.


And do not buy a new part for the tractor until you can answer this question: how do I know the part on the tractor is defective?

Once you narrow the problem to spark or fuel, post back and tell us what you found (and how you found it) and you will get plenty of help to get your tractor
running.



* Don't own an adjustable gap spark checker? Buy one! Not a test light! Until then, take an old plug, open the gap 1/4" ground it to the head & look for spark.
It’s not the color of the spark that counts; it’s the distance it jumps.

https://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/oemtools-adjustable-ignition-spark-tester/10257_0_0?
cmpid=PLA:US:EN:AD:NL:1000000:TLS:71700000043798748&gclid=Cj0KCQiAovfvBRCRARIsADEmbRKBdAvAmtFfOvYiYXR7T6NYiW57uyv5-
dEKjVT_h2KogQNUUMsRixYaAlU3EALw_wcB&gclsrc=aw.ds
75 Tips
 
(quoted from post at 15:39:50 06/06/20) Most likely one of those 6 items that you pronounced all well & good isn't. Front mount distributor or side mount? Coil require a resistor or not? If yes, what resistor is being used (style & value in Ohms). Checked fuel flow out carb bowl drain plug for a pint in 2-3 minutes?

Thanks for your reply.
Front mount distributor right next to cylindrical coil
Coil has a resistor and its been replaced as well. Resistor tests at .6 ohms
Yes, the fuel is coming out of the drain plug at the rate you suggested.

here the details of the coil and resistor
PARTS FORD Coil, Ignition 12V - Ignition Coil. This coil is used with an External Resistor if needed. Replaces OEM part numbers Case-International Harvester - 353875R91, 395331R91, 106230C91, 385403R91, AT10399, 189673M92, 189673V2., PN: D8JL12029A, $9.92, Qty: 1
PARTS FORD Resistor - For 8N, 9N, 2N, and 4 cylinder engines on 600 - 4000 tractors 1955-1964. Used in our 12 volt conversion kits. This resistor tests at .6 ohms under load through a distributor., PN: 8NE10306, $3.29, Qty: 1
 

thanks for your reply. Yes, I am using plan 1, replace everything. Primarily because the parts are very old anyway. I do not have spark gap tester, but I would imagine that it would show good spark when first started and then inconsistent spark after running it awhile.
 
" but I would imagine"

Why guess?

Confirm that you have a spark problem.....or not.

For example, the coil description says " This coil is used with an External Resistor if needed. " How do you know it needs one The only way to find out is to
measure the internal resistance of the coil. If it's 3.25 ohms or more, you do not need a resistor. And, while you are measuring, check the resistor. Some may
actually be .6 ohms as advertised.
75 Tips
 
(quoted from post at 18:10:59 06/06/20) " but I would imagine"

Why guess?

Confirm that you have a spark problem.....or not.

For example, the coil description says " This coil is used with an External Resistor if needed. " How do you know it needs one The only way to find out is to
measure the internal resistance of the coil. If it's 3.25 ohms or more, you do not need a resistor. And, while you are measuring, check the resistor. Some may
actually be .6 ohms as advertised.


The tractor was running good for a few years and I didn't make any modifications, so my thinking was something has failed or is failing. I replaced likely ignition and fuel parts but did not modify any existing configurations. The issue seems to be related to heat, as it runs well for a few minutes and then starts failing. I'm guessing that a spark gap tester would show good results during initial startup and then inconsistencies once it starts missing/sputtering?
 
(quoted from post at 10:12:10 06/07/20)
(quoted from post at 18:10:59 06/06/20) " but I would imagine"

Why guess?

Confirm that you have a spark problem.....or not.

For example, the coil description says " This coil is used with an External Resistor if needed. " How do you know it needs one The only way to find out is to
measure the internal resistance of the coil. If it's 3.25 ohms or more, you do not need a resistor. And, while you are measuring, check the resistor. Some may
actually be .6 ohms as advertised.


The tractor was running good for a few years and I didn't make any modifications, so my thinking was something has failed or is failing. I replaced likely ignition and fuel parts but did not modify any existing configurations. The issue seems to be related to heat, as it runs well for a few minutes and then starts failing. I'm guessing that a spark gap tester would show good results during initial startup and then inconsistencies once it starts missing/sputtering?
a few minutes" is a bit of a puzzle, as too long to empty carb bowl and too short to build much heat?
I support Bruce in measuring, but in absence of measuring, we can experiment, I guess. So, next time it sputters to a stop, immediately pull the jumper wire from your pocket and short across the resistor and see if it will start.
 
(quoted from post at 09:23:27 06/07/20) When it fails have you checked voltage at coil input? Could be a bad switch

thanks - will take a look at that. What is the best way to diagnose at bad ignition switch? Disconnect the switch and jump via starter?
 

Problem ended up being a faulty (and brand new) Interstate battery was causing problems with the self exciting alternator.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top