Hi,
it is really strange you have problem with six cells for the ignition. It's true that ignition doesn't work if the voltage is lower than cca 6.4V when a battery is loaded. If I understant well, after power on ignition generated the sparks but than it don't produce a spark when you close a magnet to pick up (sensor). Please could you write me if LED blink ? If not, than it is problem with pick up, otherwise a battery has low voltage when it was loaded.