IH 300 Utility 12 volt Conversion problems

[Adiredneck]

My father has an early 1950's IH300 utility tractor. It was purchased somewhere in the neighborhood of 20 years ago by my grandfather. Somewhere in the tractor's history, a 6- 12 volt conversion was done.

Dad's been having problems with the machine for a couple of years now. He always swore it was a problem with the ignition. We thought that the coil was bad, replaced it. Tried all new plug wires, etc. The engine seemed to "break-up" when it was revved slightly higher than an Idle.

The 12 volt conversion was a little messy. We went through the machine tonight & re-wired it, including a new 12 volt coil with built in resistor, new 1-wire GM alternator, etc. When it was all said & done, the machine still would not run right. By chance, we had a 12 volt deep cycle battery laying around. We bypassed all of the new wiring & ran the coil from the deep cycle battery with jumper cables. It ran great. I tested the voltage at the + side of the coil. There was 9 volts there, meaning the test battery was in serious need of a charge.

We hooked up an extra resistor that we had laying around. With the tractor off, it reads 3-4 volts at the + side of the coil (with the key switch on). When the tractor is started, it runs around 7-8 volts. My conclusion was that the coil was getting too much voltage. Can anyone tell me if the current voltage is ballpark for what the coil should be receiving? We assumed that with a built-in resistor on the new coil, that an external would not be necessary. Is this incorrect?

 

[art]

The 300's were built about 1955 and 56 and the nwer model was the 350 which looked the same just they put some white on the hood and grille. Haven't been around that stuff for a while but the resistor is to drop the current in half as 12 plus volts tends to cook the points. Are you sure it's an electrical problem?

 

[Soundguy]

Voltage doesn't cook points... It's a current issue. Due to surface area.. most of these old tractor ignition systems couldn't withstand more than 3-4 amps of primary current.

My guess is your ignition coil is not correct. You state it has an internal resistor... I've only sen a few very specialty ( like bosch) coils that actually use a resistive element. Most likely your coil is a 6v coil and really needs a dropping resistor.

My sugestion is to get a REAL, TRUE, NATIVE 12v coil.. a NAPA IC14SB and run that.

Get a new condensor and new points if yuo havn't already done that.

Make sure your alternator is charging correctly.. I'm not a fan o fthe 1 wire jobs.. a 3 wire unit will generally start charging at a much lower RPM.. and thus no need to jazz the engine. I've seen plenty of cases where these old low rpm tractors dind't make enough governed rpm to self excite the 1 wire alternators.. Sometimes.. if it is a gm 10/12SI style 1 wire.. you can run it like a 3 wire, if you have access to the spade plug area.. #2 wire loops down to the charge stud. The #1 wire runs to the switched side of the ignition either thru a 194 marker lamp bulb.. or thru a diode.. a radio shack 217-1661, or 276-1141 will work.. or any one that will carry 2-3 a, and has at least 50PIV rating. One end will be marked with a stripe.. that is the cathode.. put the cathode end towards the #1 terminal.. etc. it's pretty much automagic from there.

Fiddling with dropping resistors and 6v coils on a 12v system is just a waste in my book, IMHO.

Soundguy

 

[Adiredneck]

The coil we have installed is exactly as you describe. Brand-new out of the box 12 volt coil with built in resistor.

The Alternator is also brand-new out of the box. At an Idle, the ampmeter reads 35 amps. Revving up the engine gets us about 45 max. Perfect in my book. It's putting out high 13 to low 14 volts too.

Let's assume that we've covered all of the upgrade issues with the coil being 12 volt, the alternator being 12 volt, all new wires, etc. Can the problem just be too much spark to the old distributor for it to handle? Putting in the 6volt resistor knocks the output spark from the coil down to a manageable level?

 

[geneP]

I don't know if the dist is too weak to handle the 12v coil's spark, but my experience with putting 12v directly to a coil that is supposed to have a resistor will result in the engine running good but point life will suffer. If you haven't already, check your cap for cracks and of course your timing. If all else fails, run it for a while and see how the resisted feed works. If your spark is weak you should see fouled plugs after a short while. I know you just want to know why it doesn't work when you think everything is wired correctly, but wierd things happen. The coil could be mis-boxed or faulty or some other unforseen issue.

 

[Farmwithjunk]

I'm not very familiar with brands and/or models, but there are several very popular electronic ignition conversions for those old Binders. I'd start by asking around over on Yesterdays Tractors on the IH forum. Someone will steer you in the right direction. From what I know, they work wonderfully with 12v conversions, giving a strong, accurate spark. That way you replace your old distributor also. Then everything is new and fresh.

 

[Soundguy]

What's the make/model of the coil you bought? I havn't seen but a rare handfullof coils still being made that have an internal restive element... and most of those are specialty 'sprits car' or restoration type coils. Instead.. most manufacturers have switched to making REAL, TRUE, NATIVE 12v coils that have no restive element. The coil primary is instead the proper length and wire diameter to be of correct primary resistance.

Your symptoms sound like a 6v coil that says '12v with external resistor'.. except the chinese guy screen printing it added some chinglesh in so it may read, 12v w/ internal resistance.. etc.

In any case.. 6v coild with 12v on them will over saturate and break down ( thermal, and insulation) and cause problems like you are seeing.

Since I don't know what coil you have.. i can't offer any more advice.. except to say that i ONLY use napa IC14SB 12v coils when i need one.. they offer a TRUE, NATIVE 12v coil that performs good and needs NO resistors.

Also.. the 6v/12v issue deals mainly with the primary of the coil, which is what suffers the most. The secondary high voltage is only going to build up to a certain point before it jumps the arc.. that voltage level is set by spark plug electrode gap and compression inthe cylinder.. NOT coial primary current/voltage.

IE.. if the KV needed to jump the gap was achieved at 6v on the primary.. and lets say.. jumped the gap at 10KV on the secondary.. then adding more volts/amps tot he primary would NOT increase the secondary high voltage. IE.. making primary 12v would not yeild 20kv on the secondary.. assuming you kept the same electrode gap and realitive compression. It all has to do with insulation and potential voltage factors.. not so much with primary voltage/current. Once you are making adaquate magnetic field fromt he primary to induce the minimum voltage needed to jump the gap on the secondary.. you are there.. anything else is just -unused- potential.

High energy ignitions that have more KIV on the secondary achieve this with larger spark gaps, and /or higher realitive compression... ( which is the main benefit.. etc.. )

Soundguy

The coil we have installed is exactly as you describe. Brand-new out of the box 12 volt coil with built in resistor.

The Alternator is also brand-new out of the box. At an Idle, the ampmeter reads 35 amps. Revving up the engine gets us about 45 max. Perfect in my book. It's putting out high 13 to low 14 volts too.

Let's assume that we've covered all of the upgrade issues with the coil being 12 volt, the alternator being 12 volt, all new wires, etc. Can the problem just be too much spark to the old distributor for it to handle? Putting in the 6volt resistor knocks the output spark from the coil down to a manageable level?

 

[mich1925]

I have a 1959 Ferguson TO-35 and had the same problem. I took a resistor from an old Chrysler product to knock down the voltage to the coil and problem was cured. Letting 12 volts to the coil burned up one set of points after many attempts to make it run right. It would run ok for a while until everything warmed up and then it would start cutting out. If I stopped the engine for a while ( maybe 1/2 hour) , it would be ok for a few minutes and start cutting out again. Have not any problem in a few years of use after installing the resistor.
ron