Hello,
There is not a lot of us old school mechanics around any more I grow up with distributor, points and condenser we are a dying breed and the reason the vehicle starts when you connect the test light is there could be a ground problem.
I'm attaching a wiring diagram of the ignition system for you below. Measure ignition coil primary circuit resistance by connecting ohmmeter to C1 and C2. If resistance is less than 1 ohm or greater than 2 ohms, replace coil. Measure coil secondary resistance by removing coil secondary of wire from coil and connecting ohmmeter to C1 and C3. If resistance is less than 9,000 ohms or more than 15,000 ohms replace coil. The pickup sensor in the distributor check it an Ohmmeter should indicate 1.6 to 2.4 ohms and needle should not waver or fluctuate when the wires, grommet and sensor post are wiggled, pulled, flexed, massaged and pressed. If ohmmeter is steady and indicates 1.6 to 2.4 ohms, install dust cover, rotor and distributor cap and proceed. If ohmmeter indicates less than 1.6 or more than 2.4 ohms, or if the needle wavers or fluctuates, replace sensor. for voltage drops refer to the wiring diagram 12 volt circuit power and ground.
let us know. Please let us know if this information is helpful and if you need more info.
https://www.2carpros.com/articles/car-cranks-but-wont-start
https://www.2carpros.com/articles/how-to-use-a-voltmeter
Thanks
Joe T.
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Thursday, February 6th, 2020 AT 3:34 PM