Dodgy wiring or relay ? Possibly have constant power going to the pump u could put a multi Meter on the pump with the power off to make sure it's turning of with when the power is off
Also check what voltag u get at the pump with th power on if it's on factory wiring it will be around 10 or 11 volts any less and there could be a wiring issue
Is it wired directly to the battery or just factory wiring ? I would get the pump rewired to battery if it's factory still there is a write up in DIY section
Are u sure u put enough pressure on the line when u squezed it ?