The engine starts smoothly, but as soon as you release the ignition switch (disconnect the ignition switch) the engine shuts down. The possible causes for this phenomenon include:
(1)The connection of the additional resistance of the ignition coil is broken or the additional resistance itself is burnt out (ignition coil with additional resistance).
(2)There is an open circuit between the ignition switch "I" terminal and the ignition coil "+" terminal.
(3)Poor ignition switch contact.
The fault diagnosis method is as follows：
Check the ignition switch
Turn on ignition switch, see if the charging indicator is on. If the charging indicator is not work, it indicates the contact point of the ignition switch is not in good condition, the ignition switch should be repaired or replaced. If the charging indicator is on, then proceed to the next step of fault diagnosis.
Check the resistance between ignition switch "+" "and two low voltage ignition coil terminals with multimeter. In breaker-point ignition system, the additional resistance about 1.5 Ω. If the measured results are unavailable, it indicates that additional resistance have burn out and need to change the ignition coil. If additional resistance test is normal. You need to troubleshoot the circuit between the ignition switch and the ignition coil" + "terminal.
James Smith 
July 08, 2020