TE 20

I have a TE 20 that has been converted to 12 volt, it will only start when the motor is spinning fast and
only when you let off the starter. Ive tried running a jumper from battery to coil to no avail. Any ideas?

I'm not real clear on what you are saying. It sounds like when you release the starter it does catch and keep running is that right? It could be a weak battery that doesn't have enough juice for ignition while cranking, but as soon as you release the starter then there is enough for ignition.

That is what happens, it will not while cranking, but fires when starter disengages, as long as engine is still spinning. Does that make sense?

Yes it makes sense. I'm not a TE-20 guy and I don't have a wiring diagram for one. But if the TE-20 has a resister by-pass while the starter is engaged, that could be another area that can cause what you are describing.

That is not unusual.

Caused by a variety of reasons. There is not enough voltage to crank the engine and make spark at the same time. When you let off the starter, the voltage comes up enough to make sufficient spark, and the engine starts.

Could be a failing battery, partially discharged battery, poor connection. Have the battery load tested, feel for hot connections after cranking.

Possibly the starter is drawing too much current, usually from worn bushings. Typically it will be cranking slow, heating the battery cables, usually worse when the engine is hot.

Could have the wrong coil or coil/resistor combination. If it has a true 12v coil it should not have a resistor. If you have an ohm meter, check across the primary terminals of the coil out of circuit. Should have around 3 ohms resistance. If there is a resistor, the coil and resistor in series together should have around 3 ohms.

Could also just be weak spark in general. A failing coil, bad wires, worn or fouled plugs, bad cap or rotor, points out of adjustment, bad condenser, worn distributor bushings. It should give 1/4 blue hot spark at the plug end of each wire to ground while cranking. I'll bet you don't have that now, for whatever reason.

Another cause, (but since you tried a wire from the battery, you eliminated this) is a failing ignition switch. Especially with a switch that incorporates a start position. Sometimes the switch will loose the ignition circuit when it is turned to the start position.

Thanks for the feedback. I have a hot marine battery that Im going to hook directly to ignition but not starter and see if that is the problem.

Here is a picture of the TE wiring.