Why does my choke have to on for tractor to run?

[LeFeu]

The OP said he removed the filter, I assumed the ONLY filter that was there...and it still wouldn't run, with the same all do respect I never realized a filter before the carb on anything, let alone an old tractor was a negative.

The tractor had ran for years just fine with an in-line filter. Just one filter- and the screen in the tank.

 

[LeFeu]

Check for air leaks everywhere, even intake gaskets. Somewhere it's sucking in air besides the carb. (carb itself could also have air leaks somewhere). While running, spray a little bit of carb cleaner at various places and see if at any point it makes the RPMs go up a little. If so, then you've found the air intake leak.

Thanks Bartman,
Everything feels pretty tight - other than the butterfly shaft which I tried to remedy with an O-Ring (took away the play but won't keep running).
But I'll give the carb cleaner a try and see what happens. Thanks

 

[LeFeu]

This type should be an acceptable type to use in a gravity flow system.


View attachment 101378

Thanks Jim. That's very similar to one I removed.

 

[LeFeu]

you can try
Suggest you can pack some clean cup grease around the entire throttle shaft of that carburetor , both ends of shaft. . That will briefly seal off leak Enough . Iif iissue goes away,issue of throttle shaft this will change to normal and stay normal for a short time.

You could also if the intake manifold has 1/8 pipe plug ,remove it and put a vacuum guage instead. Then you do a vacuum test on your tractor Engine . I’ve also drill and tapped 1/8 27 pipe thread Into the intake manifold and put in a vacuum port for testing intake system. Get a new 1/8 pipe plugto ,install when finish testing, that way you have for future .
just a thought how to measure improvement of issue To get it back to normal.

Thanks Dennis. Ill give the grease a try first and take it from there.

 

[Non-farmer]

Fwiw - both of my tractors have inline plastic fuel filters. they both had them when i bought them. they both run fine. I know why one has one - rusty tank. Don't know why the other has one, but it works fine too, so the filters stay.

 

[MarkB_MI]

MarkB
Thanks for your advice. Disassembled carb again, poked fine wire through all passages followed by carb cleaner. No change.

Thanks for your advice. Disassembled carb again, poked fine wire through all passages followed by carb cleaner. No change.

I'm sorry that didn't help, although I still think you have a carburetion problem.

 

[da.bees]

I picked up on a subtle change from when you first posted that makes me believe the problem is actually ignition condenser. At first you said it ran smooth at 3/4 choke then later you said you could keep it running by "playing with choke" but it eventually sputters and dies. If you recently changed points and condenser, put old condenser back on. Otherwise if you have an old condenser laying around that with fit-up,install it. Rich mixture is easier for weak spark to ignite and a bad condenser is sporadic and quickly fades are reasons that makes me suspect condenser.
I hate throwing parts at a problem but unless you have a tester there's no option other than swapping in one known to be good. Modern condensers are crap. To date the record for me was one that started missing within 15 minutes of installation. If you buy new try to get Standard Blue Streak brand.

 

[wore out]

"It will run awhile with the choke pulled out then start to sputter and die. I can keep it going for awhile if I play with the choke but it eventually sputters out."

ASSUMING it is not losing spark that is a dead giveaway that fuel flow from the tank to the carburetor and/or through the needle and seat into the float bowl is restricted/inadequate.

Is there a screen attached to the carburetor inlet elbow, if so has it been checked./cleaned?

Could be that the float is not dropping enough to allow a full flow of gasoline into the float bowl when needed.

 

[showcrop]

The OP said he removed the filter, I assumed the ONLY filter that was there...and it still wouldn't run, with the same all do respect I never realized a filter before the carb on anything, let alone an old tractor was a negative.

Not usually, but when it is the wrong filter on a gravity system it is a problem

 

[showcrop]

You have not yet done the common test for adequate fuel supply to the carb. Testing is normally done first followed by performing the repairs/ adjustments indicated by testing.

 

[Mcrafty1]

Not usually, but when it is the wrong filter on a gravity system it is a problem

Yeah, I could have stipulated replace with the right type of filter, I took it for granted he would know to put the right kind of filter on it.....My point was DO put the filter back between the tank and carburetor. That's this man opinion.

 

[teddy52food]

If that carb is cast iron, boil it in lye water for a while, then rinse & blow all the holes & try again. If it is aluminum don't use lye.

 

[LeFeu]

Thanks to everyone who offered advice. I did a lot of checks based on your suggestions and learned a lot through it all. (I could probably take the carb apart and put it back together blind-folded now)
I think I finally found the problem. The last time I removed the carb, I noticed there was very little fuel in the bowl. I thought the float was properly adjusted, but now think it was not. I adjusted the float to raise the level and it seems to be running much better now. ( The old girl even looks a little happier now.)

Don't give up.

Spray some brakeclean around the carb while running. If the engine surges, you have air entering somewhere. Problem found.

If you didn't replace your throttle/choke tube shaft felts/rubbers, do it. Double check your float height. Check your adjustment settings.

Gave the carb a good dose of brakeclean while it was running. No indication of air leakage but the carb is a lot cleaner now!
Checked the float, I initially thought it was adjusted right, but adjusted it to raise the level in the bowl a bit and now it's running much better. Thanks for suggesting the check.

 

[scootergmc]

Thanks to everyone who offered advice. I did a lot of checks based on your suggestions and learned a lot through it all. (I could probably take the carb apart and put it back together blind-folded now)
I think I finally found the problem. The last time I removed the carb, I noticed there was very little fuel in the bowl. I thought the float was properly adjusted, but now think it was not. I adjusted the float to raise the level and it seems to be running much better now. ( The old girl even looks a little happier now.)

Gave the carb a good dose of brakeclean while it was running. No indication of air leakage but the carb is a lot cleaner now!
Checked the float, I initially thought it was adjusted right, but adjusted it to raise the level in the bowl a bit and now it's running much better. Thanks for suggesting the check.

There are youtube videos that show how to properly adjust the float. I don't know what's recommended for that carb offhand, but if it's a Marvel Schebler, it's probably 1/4". Glad you were able to get it sorted.

 

[LeFeu]

I'm sorry that didn't help, although I still think you have a carburetion problem.

Im pretty sure the problem was float set too low. Readjusted float, running much better now with choke all the way in.

 

[LeFeu]

There are youtube videos that show how to properly adjust the float. I don't know what's recommended for that carb offhand, but if it's a Marvel Schebler, it's probably 1/4". Glad you were able to get it sorted.

I actually found the video you're likely talking about. Yes it is a 1/4"

 

[LeFeu]

You have not yet done the common test for adequate fuel supply to the carb. Testing is normally done first followed by performing the repairs/ adjustments indicated by testing.

Well the first check I did was to ensure adequate fuel level in the tank. I made the mistake in the past thinking the fuel tank had fuel in it because the sediment bowl was full, but it will always be full even if the tank is empty. Then I disconnected the fuel line and opened the fuel valve and verified a good steady flow from the tank. Can't ask much more from a gravity fed system.

 

[showcrop]

Well the first check I did was to ensure adequate fuel level in the tank. I made the mistake in the past thinking the fuel tank had fuel in it because the sediment bowl was full, but it will always be full even if the tank is empty. Then I disconnected the fuel line and opened the fuel valve and verified a good steady flow from the tank. Can't ask much more from a gravity fed system.

Ah ha! but you never stated that. Congratulations on getting it!

 

[Jim.ME]

Well the first check I did was to ensure adequate fuel level in the tank. I made the mistake in the past thinking the fuel tank had fuel in it because the sediment bowl was full, but it will always be full even if the tank is empty. Then I disconnected the fuel line and opened the fuel valve and verified a good steady flow from the tank. Can't ask much more from a gravity fed system.

That is good, but there is a step beyond that. That is to pull the drain plug from the carburetor bowl and catch what runs out in a container. See if the flow stays steady, after the initial rush as the bowl empties. See if you have at least a pint or so in a couple minutes. This checks for blockage or restrictions between the tank outlet and carburetor bowl.

 

[sandhillcarbs]

Send me your carburetor, I'll Rebuild it & Clean it properly so it runs as it should

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