8n starts then quits after about a minute

[Patrick Wood]

I have an 8n 74/48 yr.
Was running rough and backfiring.
So i changed the plugs/wires/fuel filter
IT would start then quit running after about a minute.
No amount of grinding on choke would get it running of sputter even.
So I changed the points and condensor as it has been awhile.
Started right up,. Great not even any choke.
The quit like before.
So I pulled the filter in the carb. Blew it out and replaced.
Same issue.
Next I remove all the gas. Drained find into a clear container. Gas was fresh from 2 days ago.
The only thing left is the carb, I would think.
How hard is it to clean and possibly rebuild?
I used to be able to do most mechanical work myself but since the head injury some things don't always click as they should.

 

[Btzj02]

The 75 Tips has a great process to troubleshoot. In my limited experience, the first condenser out of the box always fails. I now keep condenser spares, ordered from YT, on hand.

 

[Bruce (VA)]

First, you need to tell us what model tractor you have, if its 6v or 12v and if it has a front or side distributor.



These tractors are pretty simple machines; its 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.



Ive tried all three approaches. The third one always worked for me.



I might not be able to tell you why your tractor isnt 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.


Dont guess. Troubleshoot. 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. Its not the color of the spark that counts; its 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

 

[Patrick Wood]

sorry about the type o's
it is a 47/48 8n 6 volt
the reason I changed what I changed was, for me anyway, it was time to
I changed them 3 yrs ago because I believe it to be routine upkeep.
Not just throwing money away.
It had been running not rough but would sputter once in a while.
So I changed the electrical.
Sparkplugs are gapped per manual using feeler gauge.
Points also gapped per manual.
To me no biggy but it seems to be to some.
The sputtering was gone.
Then after a few weeks, I was going to use and it started right up.
I let it warm up so it ran about a minute or so.
Then quit. No amount of cranking and choking would get it started. So I let if set and did some other things
Went back in about 2 hrs and again started right up and same thing.
Check the gas at the carb screen. Ran fine but screen looked a little clogged. Blew it out and replaced.
then pulled plug at bottom of carb. Gas came out fine.

 

[Bruce (VA)]

So it's running now?
75 Tips

 

[Jim L WA]

Patrick, in your response to Bruce, you said, then pulled plug at bottom of carb. Gas came out fine. But does it continue to run out fine. Will in fill a pint jar in a couple of minutes. It sounds like you are running out of gas for some reason. You do have the shut off valve at the sediment bowl open two full turns?

 

[IH Guy]

My 52 8n did the same thing. You could almost set predict the time it would shut down which was usually aroun 45 seconds. Sputtered the died. Go out an hour later same thing. Mine ended up being the coil which was a 6 volt replaced it no problems.

 

[Patrick Wood]

Thanks for the info.
If I wait about 10 minutes it will start with hardly cranking , then run about a minute
(never stop watched it) and then quit.
The gas will flow great from bottom drain plug on carb, I even drained the whole gas tank.
Gas looks clear.

 

[Patrick Wood]

It ran fine all the way. Drained the tank about 5 gallons. No ebbing of flow, I left the gas cap on tank to test for blocked vent.

 

[Patrick Wood]

I did get to start. Took right off. THen I ran for about 20 minutes doing some grading.
Went to change from blade to a disk so shut it off went to start and just turned over.
Checked for spark at the plugs, nothing. So traced all wires and checked for continuity. All good.
Then took a closed looked at the distributor wire, only had four strands. So replaced whole length and cleaned up connections.
same issue, no sharp.
Let it set for a day to just clear my mind and maybe get a different view.
Had a new condenser, changed that.
Started right up. Turned off and then turned back on and it started.
No issues ran great.
Disked for about 15 minutes and went to changed back to blade so shut tractor off.
Hooked up blade, tried to start back to same issue.

 

[Bruce (VA)]

Get out your meter and check the voltage at the top of the coil as soon as it stops running. Make sure the key is on. What is the voltage?
75 Tips

 

[Patrick Wood]

Will do. So measure from top stud on distributor to engine block for ground?

 

[Bruce (VA)]

Yes.

You need 2 readings.

Battery voltage ( 6.35 volts) points open.

About 3-4volts, points closed.

Bump the starter until you get 2 readings and post back w/ what you got.
75 Tips

 

[Patrick Wood]

I got just what you said I should get

 

[Smokeonthewater]

(quoted from post at 17:25:50 05/03/21) I got just what you said I should get

You got this when it quit and wouldn't start?

 

[Bruce (VA)]

Good.

Verify that your tractor is positive ground ( the cable from the positive battery post is attached to the frame of the tractor)

Now, get a piece of wire about 3 feet long and put alligator clips on both ends. Then, get your meter ready to do that same check .

Start the tractor.

As soon as it stops, check the voltage at the coil just like you did before.


If you have no voltage, hook one alligator clip to the NEGATIVE battery post ( if your tractor is positive ground) and the other end to the stud on the coil.

If the tractor runs, you have isolated the problem as being between the battery and the coil. Check each connection until you find the problem. ( HINT: check the ignition switch first)
75 Tips

 

[Patrick Wood]

will do. thanks I just replaced the switch yesterday with same result.

 

[Bruce (VA)]

OK, one less part to worry about!

Use the jumper wire and eliminate everything between the battery and coil.

Don't leave that jumper hooked up more than a minute or two w/o the engine running.
75 Tips

 

[Patrick Wood]

will do thanks

 

[Patrick Wood]

(quoted from post at 14:18:28 05/04/21) will do thanks

Ok finally got back to tractor

tried what you said no spark.

Tried a known good coil no start.

at wits end

 

[fordguy2989]

i just acquired a 1950 Ford 8N that had the same problem. this one had been sitting for about 5 years. Had no spark when i first tried starting it. Had a bunch of other electrical issues too. went through and replaced Distributor, Coil, plugs, wires and a new wiring harness. Got spark. Went through the fuel system. Petcock and the carburetor were clogged up. Replaced those along with a new fuel line. She fired right up and died after about 1 min of running. Checked my adjustments to the carburetor and the points. All good. Was pulling my hair out trying to figure it out. Turned out she was starving of fuel. The petcock says to do 2 full turns. Gave it a couple more turns and she fired right up and stayed running. Ran for about 15 mins then I shut her off and tired starting her again. she fired right up.

 

[draupo]

(quoted from post at 04:50:09 05/04/21) will do. thanks I just replaced the switch yesterday with same result.

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Sounds like fuel problem to me.
Disassemble carb and clean it thoroughly,not just the spray carb cleaner,vat it in carb cleaner.In the old days,we would disassemble and boil the carb to clean it,and immerse the float in the water to check for bubbles,which would indicate a leaking float.
Clean ALL orifices in the carb.Use a solid wire or a strand from an electrical multi strand wire.D
DO NOT USE A WELDER ORIFICE CLEANER because they enlarge the hole,which is not good in this case.
REPLACE the needle and seat.Reassemble and back out needle 1 1/2 turns to start.After starting,let it warm up,then turn needle out till it starts to flood(black smoke,and slightly skipping.Then turn back in till it starts to slow down,then back out till it just begins to smoke just a little,the go back in 1/4 turn.Now,rapidly give it full throttle.If it hesitates,back out on the bottom screw on the carb( Main fuel adjustment) a little 1/8 turn at the time little.Return to idle and do it again.You should get no hesitation when applying rapid throttle.When running smoothly at full throttle,back out on the main fuel adjustment(bottom of carb) until it just barely begins to smoke.This is a slightly flooded condition,but they always seem to run better with a slight rich mixture at full load.
These carbs are very simple to rebuild,and kits are available at a reasonable price.Instructions are available on line.Take your time and you will not have any problems with rebuilding it.
The float adjustment should be adjusted to spec using the included gauge in most kits.They are normally not out of adjustment,but check anyway.
When reinstalling the bottom adjustment,turn in till it lightly seats on bottom.Do not force it to a hard stop..Adjust out 1 turn to start,fine tuning will happen later.
Good luck!