If by pump you mean the ABS system then there are three components to the ABS syste, - Actuator, pump and valve block (plus ECU). The pump is the one with the black ball shaped unit that is used to retain the pressure. On switch on the pumps pumps fluid until it reaches the pressure. This can take up to 20+ seconds. Over time the nitrogen in the sphere leaks and it will take longer so over 30 and you need to chek things out. Also when you break, the pump pumps up the pressure again (obviously).



Spheres are no longer available but I tracked down a guy in the USA that can repair them via a mod. They were used on Volvo and a good many other cars.


I also have a series of diagnostic manuals to check out the system. My ABS light stays on now and I currently do nt know why even though it all checks out OK.