| this may be a long shot -theres a connector below the tank four wires coming out of the tank somehow the low level light supply maybe interfering with the power supply to the pump?its the only thing that i can think of that connects the pump and low level light-otherwise an intermittent fault like you have could be a plethora of things- ignoring the fact it only happens when the light comes on -coils, leaky manifolds, carbs not set up correctly(mixture,balance,throttle valves,cables not operating correctly,blocked jets)timing advancing correctly but i think you may have checked the obvious ones of this list |