Fuel pump quick (and temporary?) fix

[Reuben Lim]

First start of the day yesterday, the engine was cranking but wouldnt start. Removed the lower fuel line leading into engine and tried to start, no fuel coming out, so concluded something wrong with fuel pump. Removed the plate at the trunk and gave the fuel pump atop the tank a few quick raps while cranking, and voila! the car started. It's been fine since then, the car has died once at idle, but I've had this problem before, think its related to the idle control valve which I've already replaced.
Question: does the fuel pump only work at starting, as I'm thinking once the engine starts sucking up the expensive stuff the resultant vacuum would draw in the fuel anyways. Also, am thinking this was just a temporary fix, keeping my fingers crossed but looking around now for a new fuel pump. For an 89 M20 525, how much should these go for? Cheers!

[shogun]

The fuel pump starts when ignition is in position 2, as the whole system needs a cerain pressure. It will switch off again when the pressure is reached after abt. 5 seconds and when engine is not started.
There is no vacuum sucking the fuel when engine is running, it is the pressure from the fuel pump and that is more than the car needs. Therefore there is a or more (depending on engine type) fuel pressure regulating valve. And there is a return line for the excess fuel to the tank. And there is a check valve inside the tank that the fuel does not leak back into the tank when engine is not running or car is parked.
For the price of the pump you can check online at for example www.autohausaz.com

[Reuben Lim]

Am now looking a for a new fuel pump. Thought this was just to build up pressure for starting, didn't know this thing actually acts like the heart of the vehicle and is continually working. Thanks Erich, !