Tractor Repair: MF35 No Spark, starter solenoid, key switch

Question
I have a vintage 60's MF35 skip loader.  I can't get any spark.. I have replaced the coil, points, condenser, cap, and rotor.  Still no spark.  When I turn the motor over attempting to start, I have no spark with the coil wire off, just one spark a I let the key return back to run.  Also, what is the small condensor that attaches to the positive side of the coil and is attached to the block?  When i replaced the coil I did not use it.  Thanks for any help.

Answer
Hello,

  Use a test light or voltmeter and check if you have power to the + terminal of the coil with the key switch in the run position, and then with the switch in the start position.  After cranking it, if you get a spark when you release the key back to the run position, then it sounds like you may have a bad key switch.  At least you know the ignition system is capable of producing a spark, so the rest of the system should be good.  Also, some machines have a separate power circuit to the coil that is fed from the starter solenoid, so that it bypasses the ignition resistor while cranking the engine over to start it.  Usually, a starter solenoid will have a large terminal where the battery cable is attached, and a small terminal marked "S" where the wire from the start position of the key switch is attached to energize the solenoid to make the starter operate.  But some machines also have another small terminal on the solenoid marked "I" that powers the coil while the starter is cranking the engine.  If your machine has this, check if there is power on the "I" terminal while cranking the engine over.  If there is no power, replace the starter solenoid.  If yours does not have the "I" terminal, or if it does not have a wire on it, then it doesn't have that feature and the key switch is probably bad.