8N sputtering and cutting out

My ’49 8N is suddenly running inconsistently - for a while it runs just fine, even under load (bush hog), then it will suddenly start to cut out, sputtering and backfiring while it struggles to continue
running. Seems like it’s starving for gas or air. It can happen while under load or not - it could just be sitting out of gear idling smoothly, then suddenly start to struggle and eventually cut out. When
it does stall out, it starts back up and idles normally. Sometimes I can take off and start bush- hogging normally, other times as soon as I start under load it begins to bog down. I tried adjusting the
choke to see if that made any difference but it made none.
Here’s what I did prior to the issue starting: my Fuel Shutoff Valve was leaking gas, so I replaced the washer on the Valve Stem. I also installed a screen in the sediment bowl (had been running without
one for years). I used Gasoila (liquid PTFE) on all the fuel line threads to prevent leaks (first time using it). All fuel connections were dry as a bone afterwards.
First time out, the tractor stalled out after about 5 mins of bush-hogging. It sounded to me (from past experience) that it was NOT getting enough fuel. It would not start back up…just cranked. Next
day I replaced the spark plugs, added a drop of oil to the alternator (advanced spark) and tapped on the Carb with a wooden handle to free up the float if it was stuck. Opened up the fuel valve and then
disconnected the fuel line at the Carb and verified fuel was flowing fine to the Carb.
Started the tractor and it ran fine while I bush-hogged for about an hour - then it started it’s sputtering and cutting out issue. I topped off the gas tank so that it was close to full, replaced the oil
in the air cleaner (it was dirty, but not so bad that it would have prevented airflow). Neither of those steps cleared up the issue. Looking at the sediment bowl, it appears full when the sputtering occurs
- no bubbling (one time my gas was so hot it was boiling, which caused bubbling in the sediment bowl - that did not appear to be the issue this time).
I’ll try again tomorrow to see if it runs ok for at least an hour so I can finish my field. In the meantime, I’m hoping someone has had a similar experience. Since it’s running very inconsistently (fine
one minute and cutting out the next either under load or not), it seems to me that troubleshooting this will be a challenge.

I forgot to mention that after the problem started I also removed the screen from the sediment bowl - it appeared to me that there was an air gap at the top of the bowl. I couldn’t remember why I had been running without the screen all these years, so figured I must have heard some advice on this forum at one time to run without it.

I like to pull the plug off the carb bowl and check fuel flow there first. Then I work up to the tank if it doesn't flow. Wonder if you have a bunch of crud floating around in the bowl or maybe an ignition problem. My fergie has been sputtering around but I haven't check it out.

These tractors are pretty simple machines; it’s usually pretty easy to get them running with some basic troubleshooting steps. You can:

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.



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. See tip # 13 at the link below.


As soon as it starts running poorly, not 5 minutes later, 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. And tell us if your tractor is 6v or 12v
.



* 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

Thanks for taking the time to reply, Ollie. I'm not familiar with the "plug" on the carb bowl. Can you (or anyone) provide a pic so I know what to tinker with?

The bolt circled in red is the drain plug. If it failes the 2 min test,
the white arrow points to the fitting that has a filter screen that may be plugged. If you aren't carefull removing the brass fitting, its easy to squish the threads where the fuel line connects. I like putting an old fitting in to hold the shape, and use a flare wrench on the fuel line tube nuts until its loose.

in this upside-down view, it't the plug at upper right. it starts out life as a 7/16" hex. mine was mangled nearly beyond recognition.

it will be the lowest thing on the bottom of the carb.

Appreciate it, HFJ!

Thanks Soaked - I'm familiar with the elbow connection that has the screen (your white arrow). Tomorrow, I'll unscrew the plug (red circle) to ensure there is adequate fuel flow through the carb.

Thanks Bruce - I sent you an email.

Why the PTFE? Sounds like some of it is in the fuel line or fittings blocking fuel flow. May be in the needle/seat of the carb or in the jets of the carb. Doesn't take much foreign material to stop fuel flow.

Thanks Roger for the question. When I discovered there was a PTFE for fuel connections (Gasoila), I thought I'd give it a try. But you make a good point - in this case, I don't think I had any leakage at any of the thread connections. I doubt that any of the PTFE is in the fuel line - if it was, the issue would be occuring much more than it is - remember, I was able to run for at least an hour today with no issues. If nothing else works, I'll remove the PTFE and blow out the fuel line to the carb to see if anything comes out. I used the Gasoila on a leaking oil plug on my push lawnmower and it works like a charm - no leaks!

Sir, Might I suggest to wiggle the key in the switch to see if corrects itself.
Sounds a lot like the way mine acted. Wiggled the key, it would clear up, wiggle it again would try to shut off.
It was the switch, replaced it and back to going.
Good luck, jac

Thanks GaJack - I will certainly check that out.

This sounds crazy and don't laugh at this suggestion. The next time it starts to sputter lightly tap on metal part of the distributor with a small metal wrench. If the engine smooths out for a short time replace the condenser. You can't hurt anything by trying and you won't waste any time either!
JB

Thanks!

Problem solved - Roger in Iowa was on the right track. The Carb Screen was full of lint-like debris! I guess that's what I get for running without a Sediment Bowl Screen. Funny thing is I just checked that screen a month ago when I was working on my fuel shut-off leak. I guess I didn't give it a good enuf check. The screen came off fairly easily and I was able to scrape it all out with a small nail. I went ahead and removed the PTFE on the elbow threads to play it safe - didn't see any evidence of the PTFE at all in the screen. Now that I've loosened the screen by removing it, I hope it doesn't fall off in the Carb! Now I'll go ahead and reinstall the screen in the Sediment Bowl so I can hopefully avoid this issue down the road. Thanks to everyone that took time to respond to my plight!

Top K (Va), Glad to hear you found the problem. Thank you for posting that. So many times the poster with the problem just goes away and we never hear if the person found the problem or not.