1979 farmall wont start

i am working on a 1979 farmall 140.it started when we pulled it with a truck.got it in the shop and shut it off.now it turns over but will not start.i put a coil, points, condenser.cap, wires.i set the point gap at 20.got it to start up for a minute and it quit again .it has some kind or resister or something mounted on the coil.i plugged up the hot side the hot side of this thing to the positive terminal on the coil.getting some power to the points that way.i am pretty sure this is a 12 volt system and also the battery is weak and needs to be jumped to turn over.do i need more battery current like the 6 volt system?thanks

The resistor is bypassed in the circuit only when the starter is turning to give 12 volts directly to the coil if there is one present(resistor); the coil should be 6 volts. 12 volt battery should be installed with it otherwise there is not enough voltage.Resistor drops the voltage.

I own a 1962 farmall 140.Had trouble starting it and we had good spark and gas in the carb, so what i tried is i backed the throutle off to
the 2nd knotch and it started. Seems to start all the time now. Guess its that finicky shreibeur carbs.

Can you see a blue arc when the points break? Did you remove the carburetor drain plug to see that you are getting a good flow of gasoline?

A properly charged and healthy battery would be the first place to start.

You need to find out for sure what coil is on it. Some 12v coils require a resistor, some don't. You may be able to research this from the part number, but if not you can check it yourself.

You'll need an ohm meter to check the resistance across the 2 terminals.

First, check just the coil. Disconnect the wire from the + terminal. If the resistance across the terminals is around 3 ohms, the resistor is not needed.

If the resistance is lower, 1.5 to 2 ohms, the resistor needs to be connected.

Next, reconnect the + terminal, and disconnect the ignition wire from the resistor. Now, put the ohm meter leads from the resistor terminal where the ignition wire was disconnected to the - terminal on the coil. (Connecting the resistor in series with the coil.)

Again, the reading should be around 3 ohms. If the reading is higher, the spark will be weak.

There could also be other ignition problems. Be sure the distributor is in good working order, as in the amount of side play in the shaft bushing. If the shaft is loose, the points won't stay set properly.

Also the new aftermarket ignition parts are notorious for being bad out of the box, especially condensers. Might try the old condenser if suspect.

i am going to replace the battery as soon as i can.its old anyway.thanks

i have yellow sparks on the points itself but it only sparks sometimes on the breaker.i put a test light on the point breaker and got power there but nothing blue

thanks.ill get a voltmeter for the resister and check it .i also went and bought another condenser cause someone told me that it could be bad right out of the box.

Take a spark plug out, stuff the wire back on it, and hold the metal part of the plug against the engine block while you crank the engine over. You should see a blue spark at a regular interval.

so what u are saying is that the newer after market coils already break down the voltage to 6 for the dist.can i bypass this resister with a jumper strieght to the coil .i am thinking it would be the one to the resister coming out of the harness.i bought a new coil.thanks

I worked on a 154, that had power to
coil when key was on, then nothing
soon as it cranked. Key switch
replaced, works fine. The coil we got
required a ballast resistor. It was
printed on the coil to use one.

In the old tractor world there are basically 2 types of coils.

One is for use in 6 volt systems and has about 1.5 ohms resistance across the + and - primary winding. This coil may also be labeled "12 volt external resistor required" and needs a resistor between switch and coil input with resistance approximately equal to the 1.5 ohms of the coil when used in a 12 volt system.

The second type is a direct 12 volt coil (no resistor required) and has approximately 3 ohms primary resistance.

"so what u are saying is that the newer after market coils already break down the voltage to 6 for the dist" Has nothing to do with "newer after market coils". The distributor, points, and condenser do not care if system is 6 or 12 volts. The concern is limiting the current through the coil to about 4 amps max.

The difference in the two coils is the type of wire and/or number of turns used to wind the primary. There is no separate resistor in the coil case. It is the same difference as a 120 volt or 240 volt transformer used in household air conditioning or appliances. A transformer can be designed to work on 120 or 240 and give the same output voltage.

A tractor coil is a transformer with one side of primary and one side of secondary tied together.

thanks for the info.but i still have a problem.after i did all the tune up stuff,it fired up for a few seconds and then quit and would not start back.also i.ve heard that the points contact has to have a blue spark.they seem to do this once in awhile when i turn the engine over.i have replaced everything except the old resister that was on the old coil i put the same one on the on the new coil.i also get power with my test light at the points contact when the switch is on.it has a weaker battery also and i got it to run towing it when i first started with it .thanks for any more suggestions u might have