IH Cub Zenith Carb issue

pwatts65

Member
My IH Cub has a Zenith 13794 / 715230-91 that I rebuilt about 2 years back and its been running pretty good until now. It will run for a while till it gets good and hot and then starts sputtering like its running out of fuel then will die. Sometimes I can get it to stay running by playing with the choke but most times it will die. It usually starts right back up and repeats the issue. It has always burned rich it seems since I got it two years back.

I took the carb off and cleaned it but don't think the float is adjusted right. Can someone assist me on the float adjustment dimensions and how to measure and set it?

I have cleaned the fuel bowl, installed new screen, and even changed out the coil. Any other things that may be causing the problem? I used this tractor a lot to mow around my property and need it back up running.

Thanks
 
The next time it quits, feel the ignition coil. if too hot to keep your hand on, it is probably the problem. Checking that it has
a strong 3/8 blue spark when it stops as well. If thin and yellow, replace the coil. Jim
 
(quoted from post at 17:43:52 10/02/17) The next time it quits, feel the ignition coil. if too hot to keep your hand on, it is probably the problem. Checking that it has
a strong 3/8 blue spark when it stops as well. If thin and yellow, replace the coil. Jim

I replaced the coil cause it was so hot you couldn't touch it. Seems that the new coil is doing the same thing.

What else could cause that?
 
Check the coil resistance it is either near 2 ohms or near 4 ohms. If it is a 12v system, the coil should be 4 ohms , or if near 2
ohms, it should have a ballast resistor of about 2 ohms in line with the key and coil. Jim
 
My hydro 70 did exact same thing my mind told me it had to be fuel or carb problem since choke could keep it running. It turned out to
be the coil as stated above.

good luck
Joe
 

Thanks Jim. I'm not very good electrical but do have a fluke meter that I can use. Can you tell me how to check it? It's it across the piece mounted on the side of the coil?

Sounds like the problem I'm having are electrical related. If the ohms are low, what do I replace? The coil is new
 
Probably needs a resistor in series with the coil. Most coils are 6 volt, and use a resister if on 12 volts. A few coils are direct 12 volt, but not many.
 
(quoted from post at 19:29:00 10/02/17) Probably needs a resistor in series with the coil. Most coils are 6 volt, and use a resister if on 12 volts. A few coils are direct 12 volt, but not many.

I think it has one on it already. I have a picture but unable to attach. Could email it[/img]
 
If there is a ceramic block on the side of the coil is it wired in series (in line) with the wire from the ignition switch to the
coil? if so it is a resistor. if not it could be a part of the charging system if it has had an alternator put on it instead of a
generator.
To check total coil resistance, remove one of the two small terminal connections (either is OK) and use the Ohms setting to measure
the resistance across the two small terminals. It should be about 2 ohms if 6 volt (or 12v for use with an external resistor (which
is the same as a 6v coil)) If it is 4 ohms it is a 12v coil with no resistor required. The resistance of a ballast resistor can be
tested while the wire is off of the coil by measuring across its terminals on Ohms setting. The coil should get warm, but not hot.
Jim
 
What kind of coil did you purchase? Did you just go into a dealer and say, "I need a coil for a Farmall Cub," or did you procure it some other way?

Coils can be confusing because there are three different types:

1. 6V
2. 12V requiring a ballast resistor
3. 12V not requiring a ballast resistor

The kicker here is that #1 and #2 are the EXACT SAME COIL. #2 only exists to avoid confusion when dealing with 12V vehicles and tractors that came from the factory with ballast resistors already wired in.

#1 can be used in a 12V system if you add a ballast resistor in the power line running from the power switch.

#3 is ideal for tractors converted to 12V because it eliminates the need for a ballast resistor.

Connect #1 or #2 direct to 12V, and they get hot.
 

I bought the same coil that came off of it from the local auto parts. Which was item 3.

This one have the ceramic block you are referring too. Could that need to be replaced?

I will be at my land in two weeks and will check all this out. Thanks for the tips.

Any recommendation on the float adjustment? I still have to get the carb back together.
 

I have a picture of my set up if I could email it to someone to look at?

Unable to get it to upload to this forum
 
Picture of my coil set up attached
a173679.jpg

a173680.jpg

a173681.jpg
 

It's wired the same as it has been since i have owned it. We just recently started having all the issues.

Should I just go ahead and change it?
 
Interesting how your question about setting the float on the carb has evolved into everything about
the ignition. To me it seems you still have to proove there is an adequate supply of fuel to the
carb. Not that familiar with a Cub but I think all Farmalls had a carb drain plug. Next time your
trying it out get that plug loose and then just tighten it snug with a pliers. Then when it gives you a
fit jump off quick and pull the plug. If you get a small stream then down to a dribble you are not
getting enough gas to the carb. Generally the flow should be able to fill a pint jar in 3 minutes.
Could be something in the tank floating into the sediment bowl inlet port plugging it. Look in the
tank with a good flashlight and see if it looks like the fuel is clean around the tank outlet. Sorry I
can't help you with specifics on setting your float. Generally if the top of the float has a flat surface
on top if that is set parallel to the carb casting that is quite often close enough for these old
tractors.
 
That resistor looks to be wired (through those spotted yellow wires) to a plug that could plug into a Delco 10SI alternator. That would not be for dropping the ignition voltage, it would be to keep it from not shutting off. If one end of the resistor is going to that plug and the alternator has been replaced with a one wire alternator, that resistor is not connected, and there fore not in the ignition circuit. If the coil is getting hot, it needs a resistor (maybe not that one, as the needed resistor needs to be about 2 ohms. Mid 1960s chevy ignition resistors work well. Jim
 

Thanks for the tips. I will look in the tank again and try the pint jar. It's possible but having already went thru the fuel system I was looking at other potential issues. When it dies the fuel bowl is always full so I wasn't thinking fuel issue. Always seems to be after it gets warmed up
 

In the photo the plug was disconnected but it does hook up to an alternator that I know is not original. I actually changed it out about it two years back
 
There are none with an internal resistor. They are just designed for full 14.4 volt operation by being wound with the correct number of turns. Jim
 
I believe the shown resistor is not intended to be, and has not been in the ignition circuit. it is for the alternator #1 excite terminal. I would use a 12v no resistor required coil. jim
 

Jim

It's been like this for years, not sure to be honest if it's in the circuit or not. I replaced the coil with exactly what came out and had been running which said for external resistor on the outside of it.

I'm not very good with electrical so this is all new to me
 
Use a jumper wire and ground the terminal on the coil that is attached to the points (side of the distributor). this is like closing the points but
more sure. Use the volt meter, with the black lead grounded to the engine, to check the voltage at the other small lead on the coil (should be the
positive terminal but could be wrong) with the key on, the voltage at that terminal not running, should be either near 12v, or near 6 volts. Turn off
the ignition. This test places the coil and wiring under running load while not running. The readings tell you whether you need a coil for 12v no
external resistor required, or a 12v external resistor required. if about 12 volts, it needs a 12v no external resistor required coil of 3 to 4 ohms
resistance. If it is near 6v it needs a coil that needs an external resistor, or a 6v coil (either). If your existing coil has 3 to 4 ohms
(disconnected) and the voltage is about 12, it is as good as it gets. If your coil has 1.5 to 2.5 ohms it requires an external resistor in the supply
from the switch, or a 12v coil no resistor required.
The connection terminals on the coil should be negative to the distributor, and positive to the supply voltage. It will run rither way but is better
as noted.
A correct setup on the ignition will warm the coil, but it will not get way too hot. An internally damaged (shorted) coil will also heat up because
it acts like a wrong voltage coil. Jim
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top