DC motors come in a couple of flavors.. On one reverse the wires and it runs backwards.. This MIGHT cause damage (permenate magnet type)
On another reverse the wires and .. it don't work period (no damge) (Brushless like 12 volt comptuer fans)
On the 3rd. (ELectro magnet) it works fine no damage.
You clearly have type 3 or what follows:
I notice you said "PUMP".. There is also a different type of pump that does not actually have a motor. but a spring, disprham and electro magenet.. This works as follows
A magnet pulls a rod (Solenoid type magnet/rod) up compressing a spring and sucking in whatever is being pumped via a check valve.
Then the magnet lets go and the spring pushes it out via another check valve.
This is also works no matter which wire is which without damage.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times