Classics World



Q My 1979 MGB has been laid up for a while, and on recommissi­oning it I have a starting problem. I have got good fuel flow to the carbs, and there are new spark plugs fitted. It is fitted with an Accuspark 123 distributo­r, and the leads and coil are all clean and secure. However, the car will turn over and tries to fire, but will not start. As it tries to fire, if the ignition key is released and allowed to spring back to the RUN position, the engine will fire and run. The plugs at this point are quite wet and/or sooty until the engine is warmed through, then it runs fine and will start as it should. Once it has cooled down, then same starting problems reappear. Do you have any ideas? I tend to think it is switch/ballast resistor related, but as the switch is also a steering lock with shear bolts, I was hoping to avoid having to replace this. Mike Toulson

A The symptoms you describe all point to the problem being within the electrical contacts of the ignition switch. This would explain why releasing the key and letting it spring to the RUN position will allow the engine to fire – it is still turning slowly, but the internal contacts used when the key is in the START position are no longer connected. The spark plugs are becoming contaminat­ed and sooty because the fuel being drawn into the engine when attempting to start is not being burnt as the ignition switch is preventing the contact required for the ignition circuits to be completed, and so the engine at this stage will not fire and run. Although the ignition switch does come with the steering lock, it is possible to purchase just the switch itself (part number SSB307), and this can be replaced without removal of the steering lock. The switch is around £15 from most suppliers, and by purchasing this and plugging it into place, that would at least confirm the diagnosis before the full job was completed.

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