8n only runs with choke pulled out

clee2

New User
This message is a reply to an archived post by Nikedog on September 15, 2009 at 15:19:25.
The original subject was "8n only runs with choke pulled out".

I am having the same problem with mine. It is a 1950 side mount distributor. 12v with coil and distributor 6v. It will run and let me mow for amount 5-10 minutes then act like it is starving for fuel unless I pull out the choke. I have replaced all fuel filters along with the gas valve cut off and checked for good gas flow along with putting in fresh gas. I replaced the carb with an MS rebuilt. I also replaced the manifold and put new gaskets on. I have checked for leaks around it with starter fluid with no change in engine response. The engine does not go over 160 degrees per temp gauge. Not for sure what else to check. Again it will let me mow up to 10 minutes before acting up. Any ideas?
 
Clee2.........hazz nuttin' to do with yer carbie.......LOOSEN yer gascap. Yer top of the tank has a DOME vent that mud-dobbers like to plug-up. When the VACUUM in the tank exceeds the force of gravity, yer gas stops flowing. That takes about 5-10 mins just like you complain. FNH sells a "vented" gas cap fer NAA-600's that solves the VACUUM problem. ($15, cheap) Simple, eh? ......the vented Dell
 
I agree with Dell, hope a cleaned fuel tank cap solves your problem.

When you start having problems, shut the motor off, get off the tractor and take the fuel tank cap off, do you hear a rush of air into tank?

I am a bit concerned this may not be the problem,

If it's not the problem, normally an indicator of a stopped up carburetor is that it will run when you pull out the choke.

My old tractor will not run with the choke pulled out, only use the choke for early morning starting and then only for a short couple of pulls till the motor smooths out.
Then she purrs like a kitten.
 
Pulling out the choke gives you a richer mixture. So, you could have either a fuel or spark problem.

A carb out of adjustment will also cause this problem; set the main jet at 1-1/2 turns out & leave it alone.

A dirty carb can cause the problem as well; start by cleaning the fuel screens.

Dirty/old gas, or water in the gas can cause this problem.

Restricted fuel flow can cause this problem; remove the bolt at the bottom of the carb & check for flow. (this will tell you if the tank vent is clogged too)

On my 1950 frontmount, needing choke to run is the first sign that the points need adjusting/replacing.

A vacuum leak can do the same thing. Get a hand propane torch and carefully spray it (unlit of course) around the intake manifold at the carb to manifold interface & the manifold to block gasket of the tractor while it is running. Or, you can use carb cleaner or WD40. If it speeds up, you found the leak. Sometimes (rarely) manifolds crack or get rust holes.

Lastly, when all else fails, you could have an air leak around the carb metering section. The likely suspects are leaky throttle shaft seals and/or a worn throttle shaft. Or, just a real dirty carb w/ clogged passages.

Bottom line: Probably 90% of "needs choke to run" problems are fuel related, but do not rule out ignition problems, contrary to what others may tell you. I’ve had that very same problem before w/ a rebuilt carb, fresh fuel & good flow & a tight manifold.......and it was a spark problem. But, that was unusual. Just check the likely fuel problems first.

Please be sure to post back & let us know what the fix was. We all learn something if you tell us what worked!
75 Tips
 
Original poster said: "has a 12v with coil and distributor 6v. It will run and let me mow for amount 5-10 minutes then act like it is starving for fuel "

After checking all gas lines/carb/etc. and still have problems ?!?

I recently been working on a Ford 4000, for some farmers.

Last year, change oil/filter/, the owner said some one recently changed points/condenser/plugs, I did not check them.

Next year stated it up, warmed up engine and drove it to the shop, was sputtering and coughing, go to shop and it staled out. no start !

OK... I come to find out some one put 12V batter in a 6V system, I checked coil spark, nothing, took off coil and found a bulge at bottom of coil = a dead coil.

Possible the 12V burned out the 6V coil. replaced with 12V coil and new points/condenser/plugs ( plugs badly fowled-up and oily do to weak spark, from weak coil) and cleaned up the spark plug cables, it runs fine now. Also found old points with white and green corrosion on them.

Cleaned out the distributor with Q-tips and carb cleaner, Using dialectic grace, coated every spark plug cable connection and spark plug rubber boots and coated the rim of distributor cap ( to avoid moister entering) with dialectic grace... GENEROUSLY & THOROUGHLY !

test you coil spark first and take out spark plugs and clean/re-gap, check the coil spark to plugs also.

That's all I know
Good Luck....
 
Well I replaced the coil with a 12v and replaced the points with a electronic points. I also replaced the gas cap and after 5-10 minutes of running it will only run with choke out. The only thing left is the wiring which I am going to replace. I noticed today that the battery was dead. Hopefully it is an electrical short causing something. Still cant figure out the choke problem thought. I even tried it without a gas cap on the tank and it still had to have choke out. So not starving for gas.
 

I have replaced the spark plugs, and plug wires. Still runs for 5-10 minutes and starts lugging along. Replacing all wires on Friday and will let everyone know.
 
(quoted from post at 02:35:12 04/23/15)
I have replaced the spark plugs, and plug wires. Still runs for 5-10 minutes and starts lugging along. Replacing all wires on Friday and will let everyone know.

You stated that you checked the gas flow. How did you check it? Presence and flow can be very different. Upon removal of the plug on the bottom of the carb you need to have steady FLOW for twenty seconds. If not you have a restriction.
 
I will double check the flow. I just took apart and fuel had steady stream so I connected it back. Thanks, I will recheck just in case.
 
When you pull the choke out, you are cutting back on the amount of air that enters the carb. Since it stays running with the choke out, what you have done is created the proper air/fuel mixture ratio for the motor to continue to run.

Your carb has a choke circuit, and what it sounds like is that you are having to employ that <edit>idle (not choke)</edit> circuit for the tractor to stay running, because the main/primary/power circuit isn't working. I would pull the carb, open it up, and check the main/power jet and circuit ports to make sure it wasn't clogged with any debris.

When you take the carb off, look down the carb's throttle body (the big hole closest to the intake manifold) and with the butterfly valve closed, you will see a real small hole on the side of the cylinder wall. If you open the butterfly valve some, look past the lowest edge of the butterfly valve, and you will see a second hole. I believe these two holes (port openings) are working fine on your carb, but the throttle port (the big brass tube inside this same hole, coming out at an angle, isn't providing the needed fuel.

That'y my guess. <edit> Of course, if your tractor is sitting at idle for ~10 minutes and it dies, then ignore my post</edit>

Todd
 
Well, I went back and checked the fuel system again. All filters clear but did find a hairline crack in fuel line. Too small to drip but may have been sucking air. Changed out line and no change, still stalled. Had low flow so I changed out the new filter fuel valve with another new one and was able to run it for 5 hrs without trouble. So, even though it is a new part does not always mean that it works right. Thanks for all the advice and suggestions.

PS: My tractor did have a prostate problem with low flow but now we are good as new.
 
(quoted from post at 04:02:04 04/26/15) Well, I went back and checked the fuel system again. All filters clear but did find a hairline crack in fuel line. Too small to drip but may have been sucking air. Changed out line and no change, still stalled. Had low flow so I changed out the new filter fuel valve with another new one and was able to run it for 5 hrs without trouble. So, even though it is a new part does not always mean that it works right. Thanks for all the advice and suggestions.

PS: My tractor did have a prostate problem with low flow but now we are good as new.

Do you have an inline fuel filter, or just sediment bowl? sure sounds like a vacuum leak to me.
 
(quoted from post at 04:02:04 04/26/15) Well, I went back and checked the fuel system again. All filters clear but did find a hairline crack in fuel line. Too small to drip but may have been sucking air. Changed out line and no change, still stalled. Had low flow so I changed out the new filter fuel valve with another new one and was able to run it for 5 hrs without trouble. So, even though it is a new part does not always mean that it works right. Thanks for all the advice and suggestions.

PS: My tractor did have a prostate problem with low flow but now we are good as new.

So.........you have a new EI plus plenty of other new ignition parts....because it would only run with the choke out? I guess it was easier to spend what...... $200 for parts you didn't need than it was to troubleshoot the problem?
 
(quoted from post at 04:02:04 04/26/15) Well, I went back and checked the fuel system again. All filters clear but did find a hairline crack in fuel line. Too small to drip but may have been sucking air. Changed out line and no change, still stalled. Had low flow so I changed out the new filter fuel valve with another new one and was able to run it for 5 hrs without trouble. So, even though it is a new part does not always mean that it works right. Thanks for all the advice and suggestions.

PS: My tractor did have a prostate problem with low flow but now we are good as new.

Have you checked intake/exhaust gasket? did you check to see if nuts were tight?
 
(quoted from post at 04:02:04 04/26/15) Well, I went back and checked the fuel system again. All filters clear but did find a hairline crack in fuel line. Too small to drip but may have been sucking air. Changed out line and no change, still stalled. Had low flow so I changed out the new filter fuel valve with another new one and was able to run it for 5 hrs without trouble. So, even though it is a new part does not always mean that it works right. Thanks for all the advice and suggestions.

PS: My tractor did have a prostate problem with low flow but now we are good as new.

Thanks for posting back that you got it. I believe that EI is worth spending the money on. They save you a lot of time and ignition parts money going forward.
 
So.........you have a new EI plus plenty of other new ignition parts....because it would only run with the choke out? I guess it was easier to spend what...... $200 for parts you didn't need than it was to troubleshoot the problem?[/quote]

Actually I already had the parts for a 52 8N that I am rebuilding so I was not out any money. Since this one was already put together it seemed only logical to put the parts in this one due to both were going to be converted over to 12v with electronics anyway. Money would have been spent to do this anyway. No money loss on my part because would have been spent anyway. Just letting people know what all was going on to help diagnose and for people in future with problem.
 

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