I have a 1968 142 with power to the coil, but no spark. I have thrown all the usual parts at it : new points, condensor, cap, rotor, and coil. My Haynes repair manual says to check for battery voltage at terminal 50 at the starter solenoid and at terminal 50 at the ignition switch. I have no voltage at either terminal. I even replaced the wire to eliminate that as a problem. The repair manual just says to check the wire for breaks and bad connections, but does not elaborate on anything else. Terminal 50 is the switch input, and the yellow wire from switch to coil is the output and I have voltage there, but my alarm also went nuts, and it is spliced into the yellow wire. The alarm has been disconnected. Is it the switch? I can come to no other conclusion. Any help is much appreciated!!!

Terminal 50 at the starter solenoid and ign switch erergise the starter solenoid, you should only have power there when you actually turn the key to the start position. It won' affect the firing of the coil.

I assume your 140 doesn't have a ballast resistor at the coil, it shouldn't have as far as I know if it has it is a white ceramic rectangulat thing with some coiled resistor wires. If it has temporarily bypass it.

Your coil has two low tension connections + and - or 15 and 1, 15 being the positive terminal. your power supply should be to the positive terminal.

The negative terminal should be connected to the points in the distributor.

What is actually happening is that power is applied to the coil. When the coil is not firing the points are closed, so the power can flow. points open, magnetic field breaks down, spark is generated.

You say you have power to the coil. connect a bulb between the negative of the coil and the points instead of the normal wire. As the points open and close the test lamp should go on and off, turning the engine over with a socket on the crank pulley. One of three things will happen it will work normally. the light will be on all the time, the bulb won't be on at all.

If the bulb is on all the time you have a short on the points or condenser. If the bulb doesn't light at all you have perhaps not removed the protective film on the points, the body of the distributor isn't earthing properly.

If it does what it is supposed to reconnect to points to the coil. Pull the centre, or king lead out of the rotor cap and hold it a small distance from an earthing point, turn the engine over on the starter you should get a spark. HT IGNITION IS VERY HIGH VOLTAGE ESPECIALLY DANGEROUS FOR PEOPLE WITH WEAK HEARTS, be careful.

If you have a spark there reconnect the king lead and do the same test with one of the plug leads, If you had a spark at the king lead but not at a plug lead you have a fault dizzy cap or fauly rotor arm.

If all that doesnt work try a direct feed from the battery positive to the coil positive which will bypass your ignition switch

Regards

You might check your switch with an ohmmeter to see if #50 is

indeed connected to something else or not.

I bought one of those switches a year or two ago. I think it

cost me $8.30 plus tax. I've replaced about 3 of them on

my 164 in 30 years.