if u have DC clamp on current meter u can easily determined the current drown. if clamp on is high end type you can also determine the inrush current also. another way if u have only malty meter you can set multimeter knob to 10Amp position and place your meter lead + into 10A hole and series the pump motor connection via multimeter and start the motor.be care full your maximum current measuring limit of your multimeter.
One solution would be to use the existing pump wire to control a relay. Have the relay switch a fused line directly to the battery. If needed provide a dedicated ground wire to the battery too.
One solution would be to use the existing pump wire to control a relay. Have the relay switch a fused line directly to the battery. If needed provide a dedicated ground wire to the battery too.
I would say the 'second best' - 'best' would be to repair whatever the fault is - but this is certainly the easiest solution, and should provide a perfect cure.
Certainly a LOT easier and more reliable than trying to make a switchmode voltage converter (which would also increase the current draw, and drop the voltage further).