Super H won't stay running and is rough

[mgrafton95]

New to tractors here and looking for help! I have an old Farmall Super H. When i got the tractor, it was still a 6 volt system and would not start via the starter lever. The tractor would run, and ran pretty well; it just needed to be pop-started.

Converted it to a 12 volt system; new battery, alternator, coil, spark plugs, wiring harness. After I did that work, it ran well for a week or so. But then it started losing power while mowing and would run very rough. Assumed it was a carb/fuel issue since it ran for a while before the problems occured. I've tried rebuilding the carb I had as well as purchased a refurbished one. No luck with either of these. Currently, the tractor will start and run anywhere from 10 seconds to 2 minutes, then die. The whole time it's running rough. I'm not trying to move the tractor, just standing there messing with the idle and main jet screws on the carb trying to get it to run smooth.

I've double and triple checked that there's nothing plugged or dirty in the carb. The float works. I have a pretty steady stream of fuel coming through the line. I did notice that the coil is very hot to the touch (brushed my hand against it while pulling and cleaning spark plugs). Is it possible I got a bad NEW coil and that could be causing my issues? Would appreciate any opinions. At this point I don't know what to do.

 

[caterpillar guy]

Is your coil a true 12volt or a 12 volt needing the ballast resistor? there is a difference and will burn the actual 6 volt (12volt needing resistor)coil out. The reason it is necessary to know which you have. Also check your fuel flow and the screen at the end of the line screwed into the carb. Flow should fill a pint jar in a minute or so. It will run out fast then slow some as the fuel has to flow through the needle valve. it should still keep a good steady flow .

 

[mgrafton95]

It should be a true 12v coil. It says it has an internal resistor (https://www.link_disallowed/IHS6176-12-Volt-Alternator-Conversion-Kit-Farmall-H-Super-H-300-350)

I'll try the pint jar trick. I checked the flow pre-screen.

 

[rustred]

6 or 12 volts has nothing to do with how good the tractor runs. the coil CANNOT be HOT if it is thats the problem. people seam to create problems changing from 6 volt to 12 volt. so if you have good flow out the line at the carb full flow from line plus when removing carb plug on the bottom you will get a fast flow for 3 seconds to drain the bowl then it will trickle out at the same speed its going through the seat , normal. sound like coil to me.

 

[jimtrs]

To expand a bit on what cat guy said.
An ignition coil can get very warm to what might even be considered a bit hot, after some run time. But in no way should they get too hot to touch. As said, running a 6 volt coil on a 12 volt ignition system will eventually burn out the coil.

To determine if your coil is a 6 volt coil or a 12 volt coil, check the following. Remove all wires going to the coil. Using volt meter with Ohm reading, check the resistance between the primary terminals (two small terminals). Use the lowest scale possible on the ohm meter.


A 6 volt coil should measure somewhere around 1.5 ohms (0.8 to 2.0 ohms OK)

A 12 volt coil should measure somewhere around 3.0 ohms (2.5 to 4 ohms OK)

Ohm's Law shows those resistance numbers keeps the coil running at about 4 amps of current, just where they want to be.

A 6 volt coil running on 12 volts will be drawing about 8 amps, way too much. That will overheat and burn up the coil.

You can use a 6 volt coil in a 12 volt circuit [b:ca02cfe307][i:ca02cfe307]with the proper added resistor,[/i:ca02cfe307][/b:ca02cfe307] to limit current to 4 amps. Just use a resistor to get total resistance of coil and resistor to around 1.5 ohms.

As far as testing your existing coil, unfortunately there is no doable way with out expensive test equipment. For the average guy, the easiest way to test is to replace it with a known good coil. If that works, then yes, the original was bad.

This post was edited by jimtrs on 05/11/2023 at 09:38 am.

 

[Red Agony]

I was wondering about the polarity of the coil. When changing from 6 to 12 volt did the polarity of the ground change? If changing from a positive ground to a negative ground does the coil reflect that in respect to which wire goes to the points ground.

 

[used red MN]

Do not condemn your fuel flow if it will not make a pint a minute. Cat guy overshot a bit there that is 7.5 gallon an hour. Some of the bigger IH 6 cylinders need that much fuel but an H does not. An H May use around 2.5 gal per hour so somewhere around a pint every 2 to 2.5 minutes is a better requirement. I think it has been mentioned but try an old condenser or at least a different one.

 

[Janicholson]

coils (today) do not have resistors inside them. they are just wound with more and finer wire to operate on 14 volts Running system voltage. I fit ts a no external resistor required coil, it is bad. You also need to check charging voltage. More than 14.8 volts is too much. Jim
should say this on it.