04-05-2023, 08:07 PM
Hi Dave
The symptoms, especially the sudden onset / intermittency, make me think its more likely weak ignition than a fuelling problem. I agree that coils can fail when hot. Condensers can also fail when hot, especially modern ones. HT breakdown due to dampness usually goes away when things warm up and dry out, but some modern (i.e. not bakelite) parts like dizzy caps and rotor arms can become conductive when hot if they are not made of good enough quality plastic.
Clean the points, then draw a switch cleaner soaked piece of business card through, to remove any particles
Check the earthing of the points via the distributor to the engine block. This can come and go with vibration if dodgy.
LT feed to coil from the ignition switch OK ? Try a direct feed if suspect.
A voltmeter will be useful when checking the LT side of the ignition. Expect no more than about 0.5 volt drop from the battery to the coil SW terminal, and no more than about 0.2 volts drop from the coil CB terminal to the engine block. Both these checks carried out with the points closed and the engine not running. If you can use croc clips for the probes, it leaves hands free for wriggling connections, ignition key etc to test for intermittency.
The symptoms, especially the sudden onset / intermittency, make me think its more likely weak ignition than a fuelling problem. I agree that coils can fail when hot. Condensers can also fail when hot, especially modern ones. HT breakdown due to dampness usually goes away when things warm up and dry out, but some modern (i.e. not bakelite) parts like dizzy caps and rotor arms can become conductive when hot if they are not made of good enough quality plastic.
Clean the points, then draw a switch cleaner soaked piece of business card through, to remove any particles
Check the earthing of the points via the distributor to the engine block. This can come and go with vibration if dodgy.
LT feed to coil from the ignition switch OK ? Try a direct feed if suspect.
A voltmeter will be useful when checking the LT side of the ignition. Expect no more than about 0.5 volt drop from the battery to the coil SW terminal, and no more than about 0.2 volts drop from the coil CB terminal to the engine block. Both these checks carried out with the points closed and the engine not running. If you can use croc clips for the probes, it leaves hands free for wriggling connections, ignition key etc to test for intermittency.