farmer-rich118 Posted October 12, 2020 Share Posted October 12, 2020 Exchanged motors in my 900 series garden tractor. Can’t get a spark.....except when you shut off ignition...one spark!. Have changed plug, coil,condenser , battery.....still only spark when turning ignition off. Any help, much appreciated. Quote Link to comment Share on other sites More sharing options...
Ronald Hribar Posted October 12, 2020 Share Posted October 12, 2020 Did you put same type of engine back in.? did you change wiring at all did you ground motor? Quote Link to comment Share on other sites More sharing options...
SmilinSam Posted October 12, 2020 Share Posted October 12, 2020 55 minutes ago, Ronald Hribar said: Did you put same type of engine back in.? did you change wiring at all Thats what I was questioning too.... Quote Link to comment Share on other sites More sharing options...
Brettw Posted October 12, 2020 Share Posted October 12, 2020 If you went from a battery ignition to a ground to kill engine (read: Kohler to Briggs) you need to change out the ignition switch, or add a relay. The ignition switch on battery ignition provides battery power to a coil for spark and turns off battery power to kill the engine. On the other, the engine provides it's own power through a magneto type coil, and the ignition switch grounds out the spark when killing the engine. That could very well be your issue, by the sound of it. Quote Link to comment Share on other sites More sharing options...
GregB Posted October 12, 2020 Share Posted October 12, 2020 And if it was a KT and a Magnum was installed, the Regulator is possibly fried. Quote Link to comment Share on other sites More sharing options...
farmer-rich118 Posted October 13, 2020 Author Share Posted October 13, 2020 Thanks so much for the responses! i replaced a 12 hp Koehler with. 16 hp Koehler. They were both out of the same 900 series AC tractors. The wiring appeared to be the same. Quote Link to comment Share on other sites More sharing options...
farmer-rich118 Posted October 13, 2020 Author Share Posted October 13, 2020 Brett, how do I determine if the motor is a ground kill or battery ignition? Quote Link to comment Share on other sites More sharing options...
farmer-rich118 Posted October 13, 2020 Author Share Posted October 13, 2020 And , isn’t the engine grounded just by the fact that it’s bolted to the tractor frame? Quote Link to comment Share on other sites More sharing options...
PhanDad Posted October 13, 2020 Share Posted October 13, 2020 5 hours ago, farmer-rich118 said: how do I determine if the motor is a ground kill or battery ignition? Check for +12v when the ignition switch is in the "start" or "run" position and no voltage in the "off" position. This is what both of a stock Kohler 12HP and 16HP engines require. A battery ignition has an external coil mounted somewhere on the engine. In order for the engine to run, you need to supply +12v to the coil. The "start" and "run" positions of the ignition switch provide the voltage; in the "off" position, there is no voltage supplied to the external coil. A "ground kill" ignition system is a magneto system where the coil is under the tin of the engine. Magnets imbedded into the engine flywheel spin past the coil to generate electricity. When both legs of the primary circuit are grounded, there is no current flow. The "off" position of the ignition switch grounds the side of the circuit that is normally opened by the points (or electronic ignition module). 5 hours ago, farmer-rich118 said: And , isn’t the engine grounded just by the fact that it’s bolted to the tractor frame? Yes, the electrical system is negative ground 6 hours ago, farmer-rich118 said: i replaced a 12 hp Koehler with. 16 hp Koehler. They were both out of the same 900 series AC tractors. The wiring appeared to be the same. I'm not real familiar with Kohler equipped AC tractor wiring. Might the engine connector wiring be different between the engines? Make sure there is +12v going to the external coil when the ignition switch is in the "run" position. Quote Link to comment Share on other sites More sharing options...
Tarheel Posted October 13, 2020 Share Posted October 13, 2020 From what you are saying about the spark when you turn off the ignition, it sounds like you have the right ignition type for the wiring on your tractor. IE a Briggs magneto would not spark when you turn off the ignition switch. Working from there, Being that you do get a spark, we know (assume) your coil is good and is getting voltage. (From both positive and negative) The ignition works by running 12 positive to the coil from the switch and if you follow the ground lead, you should find it routes to the points. If you remove the cover on the points and rotate the engine by hand until they are open, Then turn the key on and off, (don't engage the starter) If you get a spark then the ground lead or points are grounded full time. The points are a small switch and if there is a gap between them, the coil should not get ground. So should not spark when the key is turned on or off. If you get spark in this case (points open) then look for a short in the wire from the negative terminal on the coil to the points. A bare spot on the wire etc. If no short is found then I would replace the condenser as they can go bad and ground the points. If you have a volt/ohm meter or a 12 test light you can test that way. with a test light put the clip on the positive and the probe on the negative of the coil. Turn the engine over and you should see the light turn on and off. If it stays on full time then you have a short. If it don't light then you have dirty points and so on. 2 Quote Link to comment Share on other sites More sharing options...
farmer-rich118 Posted October 13, 2020 Author Share Posted October 13, 2020 Tar Heel, thanks, I will investigate this further In the morning armed with your info...... Quote Link to comment Share on other sites More sharing options...
Cityboy Posted October 16, 2020 Share Posted October 16, 2020 The PTO isn't engaged, is it? Don't ask how I know about that one! It would prevent starting. Quote Link to comment Share on other sites More sharing options...
MikeES Posted October 23, 2020 Share Posted October 23, 2020 I had a bad ignition switch on one of our pulling tractors. It would fire and start when I let go the key from the start position. Drove me nuts until I check the switch and found out I had power to the coil with the switch on, but no power to the coil with the switch in the start position. 1 Quote Link to comment Share on other sites More sharing options...
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