I finally have a working ignition system. The tach was fine with the Hella Ignition modules and Beru 0.8 ohm coils But following the failure of the Hella modules and no working Hella replacement available, I switched to Petronix ignition modules with Petronix 0.6 ohm coils - as per Petronix's recommendation (to not damage the ignition modules). On acceleration, the tach goes spiralling off before falling back to the correct level. i.e. if I accelerate sharply, the needle will fly round to 6,000 rpm before dropping back to the correct 4,000 rpm. Before anyone suggests it, the clutch isn't slipping! Since the tach's only connection to the car is a wire to the coil, I'm guessing this is where the problem lies. I've seen a few similar posts over the years but not with this exact behaviour. I do have a couple of ideas but I won't muddy the water at this point. I'd be grateful for any suggestions!
