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TO30 no spark

P

Patrick Wood

Member
Hi, all
My brother has a to30 with a 12 volt conversion but he kept the 6 volt coil with a rectangle resistor.

It was running fine for yrs (8) he parked it yesterday and now wont start.

I replaced all the spark plug and distributor wires as they were corroded.

Same issue.

Checked voltage to the switch 12v, from switch to resistor 12v, from resistor to coil. Nothing.

Both sides of coil 12v.

Could not check ohms as his meter was not working in ohms. What should the reading be?

Could we just remove the resistor and get a 12v coil?
 
Sounds like the points are not making connection.

Turn the engine until the points are closed, turn the ignition on, then take the voltage reading.

If the points made connection, the voltage to ground on the points side of the coil should be zero. If the points are closed and voltage is still on the distributor side of the coil, the points are needing to be cleaned or replaced, or there is a bad connection between the coil and the points.

Once the connection is made, and the voltage on the distributor side is zero, the ignition side should read around 6 volts after the resistor, battery voltage ahead of the resistor.

Take your readings quickly to avoid overheating the coil.

While dealing with the points, check the distributor shaft for side play. If it is worn the points will not stay set and will be short lived. Todays points are not the quality they once were, everything has to be right. If they lasted 8 years, that is wonderful!
 
I bet the rubbing block on the point set is worn down with age. Napa used to make decent quality. As for the condenser, you old one might be better than a new one.
a 12V coil should work just fine. Make sure it says "Internal Resistor".
12V on the (NEG) points side of the coil indicates the points are probably not closing making the ground circuit side of the complete.
That open circuit explains why the points are not firing. Good chance the points are oxidized and you might be able to make it start and run by using a points file and re-gapping them. No points file? Nail file will also work. However, as the points are probably arced from burning and the oxidation is what is keeping them from closing filing them might only serve to give them a shorter life.
Me? I might buy a new set, but file them anyway just for the entertainment factor. Then see how long it runs.
 
Thanks to both of you for replying. I will let you know what I find out this weekend as the tractor is up on the family farm about 70 miles away.
 
70 miles one way is what I drove to work for three years.
700 miles per week.
I fail to see a problem.
You should be able to do that after work some day.
Just kidding. Catch you later!!
 
I did 2.5 hrs for a year. THat was enough.
I go up there and checked the points and they were opening and closing fine.
With the key turned on, there was spark.
Pulled all plugs and they were clean but when checking for spark, nada.
Pulled one of the new plug wires, no continuity.
Checked the rest plus the coil wire same issue.
Made new ends and all had continuity.
Tractor took right off.
Tried multiple times. good to go.
Cleaned up tools and tidies up wires.
Tried one more time, no go.
Checked at switch only got voltage on wire coming from ammeter. Hard to believe the switch would go. Cleaned up all connections on switch. same thing.
 
Intermittent switch due to arcing at the internal point connections.
I say it needs a switch.
It's how old?
 
I just went through the same issue. If it were closer I d suggest you try starting it on the second position ( the light position) . Mine would start and run by doing that, then turning the lights off to the run position on the key switch, it would run for a few seconds and at the slightest bump or vibration it would die. The issue came on suddenly as many do with these 60+ year old tractors.
 
Well, not the switch.

Same issue, no spark.

wire from ammeter 12 plus volts

wire to resistor no voltage key on or off. Measuring from key wire connect to ground.

No voltage on coil side of resistor with key on or off.

WTH I am missing?
 
Do you have power to your key? Seems to me you have a bad connection somewhere either at the key switch or before. I use a lighted test pick, find a good ground and pick away...you ll find it fast.
 
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