Farmall Cub

Hello Everyone,

Im new here so please be easy on me!

Have a 1948 farmall that Im trying to get running right for a family friend.

BEFORE: tractor would start and run like a champ for 20-30 minutes but then cut out and once it started doing this, would need to sit for 30 min- hour before it would run correctly. However the tractor would always immediately start back up after dying.

SO, after getting my hands on it, I rebuilt the carb to clean it out and repair seals that were leaking in it, found a bare wire contacting metal, added the clip that holds the needle to the float in the carb that was missing, tested the condenser and coil on a multimeter ( appeared ok). I also repolarized the generator and replaced the battery as it was shot.

AFTER: Tractor will now run for 45 min-1hr before it has the same problem. Battery is charging from the generator.

See the video of what it does after that time...any ideas???
http://www.youtube.com/watch?v=gbNzxQjMrno

In your description, it sounds very much like a failing coil, but watching your video, I'm inclined to think it's more a fuel flow issue. Check your fuel flow at & through the carb. Also check the fuel cap vent holes, if the tank's not venting, it will act exactly as it's doing.

By the way, welcome to the forum! We have only a few chosen one's we beat on regularly.

Replace the coil.

Edit: The video sounds like a fuel flow problem. But the 45 minute to hour run before the problem occurs is confusing. Normal fuel flow obstructions only take a minute or two to appear in engine performance. Unless you only have a small restriction in the fuel flow - not quite enough of a fuel flow to fully keep up with carburetor/tractor usage.

Eugene, that's why I dwelled a bit on the fuel cap, sometimes it takes a while for that to show up.

Welcome to the forum. After watching the video, unless there was a time lapse between the stalling and restarting, the problem acted like my H did several years ago. It would idle fine, but die under load. I finally found a piece of an old fuel cap gasket had fallen into the tank and made its way into the shutoff, letting gas flow slowly, but not allowing full flow, acting as a check valve. Probably a long shot, but you might want to check. Good luck! John

As soon as it stalls yank the gas cap off and listen for a vaccum sound. it seems a lot like the tank not venting. Does it only happen under load or will it do it at an idle as well?

Well guys, I tried leavin the fuel cap loose last time. There is some debris in fuel supply ( i have seen alot poorer tanks). Keep in mind this was after an hour.

Not sure what to think of this but with cultivators down, upon restart, loading up the clutch will stall it going forwArd but not reverse

My experience suggests its still coil since heat decreases coil efficiency and cylinder pressure will take more energy to fire. Load being cyl pressure etc...

Does it matter if the coil bench tested? Probably not considering its the heat that I was suspecting...

Thanks for all the help and that was real time approximately 1 hour into running on a sunny breezy 80 degree day.

EDIT: so it would run 30 min with corroded loose connections and a crap battery, now it runs 60 min with a new battery and clean terminals, and a working generator...sure sounds like a bandaid for a weak coil now that i think about it.

Someone also mentioned a screen the the inlet elbow at the carb body. I blew that brass elbow out and disconnected the section of hardline but did not remove the elbow from the body. There are no inline filters ( thinkin about puttin one in) but the carb was gutted and i checked the stand pipee in the tank once when it stalled and it looked clear ???

The problem with it being a fuel flow issue is how long it takes to appear. Either a fuel flow issue will show up right away if it's a cap/line thing, or at random intervals if you have "floaters" in the tank.

Since it is happening after a regular interval, I would put my money on electrical.

Coils are $25. Not a huge expense. Worth a shot if you ask me.

I was having the same issue on my 51 cub. I replaced the coil, fixed the vent on my fuel cap and found my newly rebuilt carb needed the float adjusted 3 times BUT now it runs like a Singer sewing machine. Good luck buddy. Btw these guys on here truly helped me with my entire restore. Greatest forum around.

To comment on your question about bench testing the coil - In my opinion it means nothing if the coil bench tests good. You are correct in that the heat is the problem. I would substitute a new or known-good coil for yours and see if that doesn't cure the problem. You may still have some fuel issues but my money is on the coil as your main problem and it is causing the symptoms you describe.
If a coil bench tests bad it is probably bad. If it bench tests good, it could still be bad.

Update:
Replaced coil this morning and rebuilt generator side of harness. Also put in brand new sediment bowl with screen and shutoff. Now it ran for 20 minutes...

Rebuilding the coil harness to console now. The wires are so old and brittle. It sure does act like electrical.

Anyone seen a main so leaned out it dies when hot??? Thats the only fuel thing I can think of...

EDIT: im pretty sure I was just able to make it sputter and keep goin for a few seconds using the choke. Ughhhh! This thing drives me nuts! Even though ive repaired all the cobble job wiring the right way that obviously tells me its back to " air or fuel"... Too lean main setting, cracked intake, or bad adjustment on the floats. I set the zenith floats at 1 3/8. Can I fill it up more? I gotta get my hands on some propane or somethin.

That is acting just like my 140 when i got crap in the fuel line.

I assume you checked the fuel bowl inlet screen (I think you have one on the Zenith). This screen is very easy to clog up.

And you checked the the flow coming from the tank. (it should be a strong steady stream of fuel)

Any resolution on this one yet? Interestingly following this thread.

No resolution. Rebuilt carb and brand new sediment assembly. Owner swears it ran 2 hours straight the other night with no hiccup. Strong stream to inlet of carb...headed back tomorrow for one last stab at it!