Massey Ferguson TO35 ignition

[CRAFT]

I have a Massey Ferguson TO 35, gas burner. I changed it from a 6 volt positive ground to a 12 volt negative ground, some 50 years ago. I purchased an electronic ignition from Yesterday's Tractor many years ago and ran it with a coil with a internal resistor and a external resistor for many years. Then the tractor was in a fire and I had to restore it. I replaced the distributor and all the damaged parts. Then I ordered a new electronic ignition from Yesterday"s tractor. The directions said to remove the external resistor. The system lasted less than a year, but not many operating hours. It was replaced under warranty. That one lasted about 6 months, but not many operating hours, before failure. I need advice.

 

[Jim.ME]

What part number EI did you purchase?

What part number coil did you purchase? If you purchased a 6-volt coil like you had originally an external resistor is required when used on a 12-volt system. If you purchased a true 12-volt coil, no external resistor is required. There is no resistor inside of a true 12-volt coil, the coil is wound internally to have the required resistance.

What type of sparkplug wires did you install?

 

[Ericp351]

The concept from Mr Jim, above, may prove helpful, but stated awkwardly. Stated simply. Nearly all coils are really 6v. When used at 12v you do knock down volts with a resister. Otherwise expect point burning . Nearly all car makers, not stupid, used external resisters with point set ups. CRHYSLER style external ballast resisters at about 1.5 ohms are popular with tractor 6v to cheap 12v GM alternator conversions. This concept is decades old. Ford used register wires, Chrysler, above, et. Cetera. Check a known good coil, 6v, 12v, whatever. You will see simular 1.2 to 1.9 ohms. Yes, you can buy a "super duper 12 v ready" coil. They are a common coil with a resister INSide, pre installed. That way , you pay more for a coil that if the register goes bad, you toss a whole $39 unit. Trivia, Ford, via the starter solenoid, would by bass the EXTernal resister for start to gain a temporary cold start hotter spark. Kind of neat and adaptable to your tractor if desird. In your case, going to points would be much more reliable. Cheaper also. Down side is a bit of simple maintenence. Cobble up a 6volt tractor [6decades old] with conversion to 12v ( 1970,s teck) then re convert to point less with low volume selling mystery parts (early 1980,s teck) ain,t the way to be reliable , or long term serviceable. Toss in a low volume " cute coil"- built in resister, (silly marketing) that OEM refused, and , well, maybe ya see where I'm going..

 

[Jim.ME]

The concept from Mr Jim, above, may prove helpful, but stated awkwardly. Stated simply. Nearly all coils are really 6v. When used at 12v you do knock down volts with a resister. Otherwise expect point burning . Nearly all car makers, not stupid, used external resisters with point set ups. CRHYSLER style external ballast resisters at about 1.5 ohms are popular with tractor 6v to cheap 12v GM alternator conversions. This concept is decades old. Ford used register wires, Chrysler, above, et. Cetera. Check a known good coil, 6v, 12v, whatever. You will see simular 1.2 to 1.9 ohms. Yes, you can buy a "super duper 12 v ready" coil. They are a common coil with a resister INSide, pre installed. That way , you pay more for a coil that if the register goes bad, you toss a whole $39 unit. Trivia, Ford, via the starter solenoid, would by bass the EXTernal resister for start to gain a temporary cold start hotter spark. Kind of neat and adaptable to your tractor if desird. In your case, going to points would be much more reliable. Cheaper also. Down side is a bit of simple maintenence. Cobble up a 6volt tractor [6decades old] with conversion to 12v ( 1970,s teck) then re convert to point less with low volume selling mystery parts (early 1980,s teck) ain,t the way to be reliable , or long term serviceable. Toss in a low volume " cute coil"- built in resister, (silly marketing) that OEM refused, and , well, maybe ya see where I'm going..

Please show the part number of a currently available 12-volt coil with a resistor inside.

For years coils have been wound (the wire coils inside sized and the number of turns) calculated to provide the required resistance for use on a 6- or 12-volt system without an external resistor. If a 6-volt coil is used in a 12-volt system, it needs a resistor wire or external resistor ahead of it to reduce the voltage/current to the proper level as to not burn the points.

Many manufacturers used the resistor bypass terminal on solenoids, in the early years when using a 6-volt coil and a resistor in a 12-volt system to aid in starting.

In the case CRAFT asked about, there is a chance he his having short life from the 12-volt EI system if he used a 6-volt coil without an external resistor in his 12-volt system. There is a case where if one is going to run EI they should use coils having the recommended ohms of resistance for the EI unit. In this case where he is replacing fire damaged components, why would it not make sense to go with a straight 12-volt coil of the ohm rating required?

It seems he wants to stay with the EI system as he has not mentioned reinstalling points. If he wants to go back to a points system, then a 6-volt coil and external resistor and a bypass circuit would be a good option.

 

[Ericp351]

Mr Jim, and Craft, number 1, good w e agree as to going back to points principal, Mr. C,s call. Wanted to make case. For simplicity, let's keep with applicable Points era and applications as his tractor was built for same. No, I did not memorize the Nappa, 3 ish ohms coil, often referenced in the web thingy. It is proported to be marked or listed as 12volt drop in or some such. I expressly did not advocate for it. As to 12v coils, I completely disagree. Tractors and cars nearly always provided for external resistors.


Drivers for years carried a Mopar ballast register, ceramic, in their glove boxes. If your car started nicely, then died, you swapped it easily and went to work. 1 screw into firewall, 2 slip tabs for wires, some had 4. I referenced Ford cars. My Mf 35 has a threaded hole in coil bracket for a "piggy back" resister. 1960, original 12v. Coils are important, yet stupid. They can not read the stickers they may carry. Most are about 1.5 ohms and like to be fead about 6v, battery, or really 7.x volts, operating. V equals l, Current, times resistance. Double the volts, example is 6 to 12, and current stays static IF you more or less double resistance. My generality is and was about 1.5 ohms common coil, more or less 1.5 ohms for any external register, common, or jump to 3 ohms coil, less common. Again, volts drop in proportion to resistance. Current don't care if resistance due to snazzy coil, or plain old ballast register. You start at 12v, pressure, end at 0. Drop all at coil without allowances, and twice the volts is twice the heat and component shorter life. Here, the gentleman had ,probably, a 6v positive ground tractor. Points. First somebody changed ground, battery, and added , probably, a Gm style alternator in place of a 20 ish amp generator. 1970 teck if internal volt reg. Then maybe a coil change, maybe a external resister, diode, fuse link, whatever, plus an early 1980s teck Hall effect, or not, points eliminator kit. Without thought and integration, it is a wonder it ran for even a hundred hours without failure or a fire. Time to pretend it is 1950, plus or minus, and work out a reliable system, as the tractor maker did. Keep any working alternator, paired to any good battery, reasonable wires and gage, 3 ish total ohms, OK coil, simple , proven points, and done. Otherwise, try to match a coil "kit" to alt " kit" to points eliminator " kit" and continue to see what happens. Sounds like more down time latter, or head scratching now. More cost, time, less reliability. Yes , can be done, especially for a hobby tractor. Again, coils don,t have magic wires that tell them what battery is in the system.

 

[Jim.ME]

I am trying to work with his apparent preference for EI, not muddying the discussion with the old points vs EI rhetoric. He is looking for info on why he might be having short EI life since the fire repair compared to the life span of his earlier EI.

 

[kencombs]

I have a Massey Ferguson TO 35, gas burner. I changed it from a 6 volt positive ground to a 12 volt negative ground, some 50 years ago. I purchased an electronic ignition from Yesterday's Tractor many years ago and ran it with a coil with a internal resistor and a external resistor for many years. Then the tractor was in a fire and I had to restore it. I replaced the distributor and all the damaged parts. Then I ordered a new electronic ignition from Yesterday"s tractor. The directions said to remove the external resistor. The system lasted less than a year, but not many operating hours. It was replaced under warranty. That one lasted about 6 months, but not many operating hours, before failure. I need advice.

What is the actual maker of the EI kit? there has been a lot of discussion, here and other web sites, about Pertronics units having chronic failures.

But, just as many folks will chime in with good experiences. I don't know the answer, just that your experience may not be something wrong with your tractor or installation, but a quality control problem from the maker.

Regarding coil choice, I would trust the instructions, use the correct coil and have another discussion with the provider of the kit.

What I would verify is current draw after it's repaired. No matter what combo of coil and voltage you have the current draw should not exceed 4 amps.

The early GM HEI units used circuitry that shortens dwell time at low speed in order to limit current at idling rpm. I have a suspicion that other EI controllers may not do that and the resulting current flow may lead to early failures. Just a guess.

 

[Ericp351]

OK, as to the electronic . I,ll simply, briefly, advise, points or points eliminate kit. -------- Step 1 is shoot for 1.5 ohms per 6 volts. If he first went to 12 volt, than bought a kit for a 6 volt tractor, trouble could be that simple and easy to check. I still say a coil is a coil, they don,t care what box they come in. Adapt system fast and cheap as I layed out if mismatch. Also, points is fastest , cheapest, and most sure way of operating the tractor. Good luck. Getting hung up on a lable is still counterproductive.