Ignition related running problem
Posted: Thu Mar 11, 2010 9:43 pm
I have a 1968 plus 2 with a psoitive earth tacho. The car had been converted to run negative earth before I bought it and the tacho runs erratically The car will start and run well for a short while. When the engine is hot the car starts to miss particularly under load and then shortly cuts out completely. After allowing the car to cool it will start and run again untill it is hot then fail again.
As part of diagnosis I have run a wire directly from the battery to the coil, and disconnected the tacho supplied feed. The strange thing is the tacho continues to work although still erratically.
I have thought it was the coil breaking down but have replaced the coil as well as the condenser and the same thing happens.
One other thing to note is that the central graphite 'plunger' contact in the dizzy cap has almost dissapeared- eaten away presumably.
Searching on here I have seen a comment re the ignition switch building up a resistance and breaking down. Is this possible?
Also with the change to negative earth previously, is it possible that I have connected the coil sw and cb sides back to front. If so would the car still run?
Any ideas on what's going on?
Thanks
As part of diagnosis I have run a wire directly from the battery to the coil, and disconnected the tacho supplied feed. The strange thing is the tacho continues to work although still erratically.
I have thought it was the coil breaking down but have replaced the coil as well as the condenser and the same thing happens.
One other thing to note is that the central graphite 'plunger' contact in the dizzy cap has almost dissapeared- eaten away presumably.
Searching on here I have seen a comment re the ignition switch building up a resistance and breaking down. Is this possible?
Also with the change to negative earth previously, is it possible that I have connected the coil sw and cb sides back to front. If so would the car still run?
Any ideas on what's going on?
Thanks