702 not firing

[WH1618speed 432]

I've been putting my 702 back together after a restoration and it turns over but there is no spark. According to the test light, there is power coming from the on/off switch to the coil and the light flashes on when placed on the negative terminal where the points and condensor are located. I got it to start earlier with starting fluid but I am getting nothing now. It is getting fuel to the carburetor. Choke and throttle are open. I tested the spark plug on a different tractor and it works. I am lost. 

[Pullstart 60,068]

All your grounds good and clean?  Can you trace power through the switch and to the coil?  Make sure to check power to the cook, when the engine is cranking too 

Edited October 21, 2022 by Pullstart

[ri702bill 7,442]

It may be as simple as oxidation on the points - particulary if the points are new. A crisp new dollar bill dragged thru the points when closed can do wonders...

[oldlineman 1,453]

Have to do that every fall to my old Sears snowblower with a tecy engine,to get it to fire, pain it the  because points are behind flywheel.

[953 nut 52,132]

Is the ignition coil the proper internal resistance type.

 

There are three main types of coils that find their way into the points-based tractors,

 

1. THE CORRECT COIL = this coil has a “internal resistor" within the coil body that restricts the amount of current that flows thru the points and coil combo. The internal primary resistance of this type coil can be measured with a multimeter at about 3 - 4 ohms. If 12 volts powers a 4-ohm resistance, 3 amps flows and that equates to about 36 watts of power - warm but not hot.

 

 

 

 

 

 

 

2. INCORRECT COIL - REQUIRES EXTERNAL RESISTOR - this look alike is visually identical to the correct coil but its internal wiring can overheat if an "external resistor" is not used in series with the coil. The primary resistance of this coil will be in the 1 - 2-ohm range. The external resistor accounts for another 2 ohms. Properly configured, this combo is the equivalent of the 4 ohm internal resistor coil discussed above.

 

If this coil is used alone, the electrical system will see the lower resistance and double the current flowing thru the coil and points. The result is over-heating the coil and premature eroding away the point's contacts.

 

12 volts powering a 1.5 ohm circuit equals 8 amps of current flowing and generating nearly 100 watts of heat and energy. We are now seeing the coil get hot.

 

 

 

3. ELECTRONIC IGNITION COILS - these are the high energy bad boys of the ignition world and demand gigantic gulps of current to operate as intended. They will fry points within minutes. The primary resistance of this style coil is usually well under 1 ohm and current draw can be near 20 amps. These coils are fine if you drive them with electronic ignition modules. They will fry GT wiring very quicky. 20 amps of current flowing thru this circuit generates over 200 watts of power. Wires melt, points vaporize.

 

Measure your primary ignition coil resistance. Anything less than 3 ohms and you have either a shorted coil or an incorrect coil on the tractor. A correct coil should be labeled "12 volts" . If you see "external resistor required" on the coil or the coil looks like it came out of a spaceship, you have the wrong coil.