A pump works against gravity by pulling water up through a spicet. As you "pump" the handle the air is removed from the line so ultimately in time you are pulling up the water from the reserve.
how does a rotatory pump work
If the relay is bad, then the fuel pump will not work.
Bad fuel pump?
A blockage in the downstream side of the pump could make this pump work harder raising the amps as the pump now has to do more work to get through the line. An upstream blockage would make the pump spin more freely lowering the amps on the pump as it will not be doing any work.
you pump the water out until it comes out
You cannot do that. The pump impeller blades will only work one way.You cannot do that. The pump impeller blades will only work one way.
The pump does work, but there is very little fluid movement in park.
Yes, it is a fuel pump relay.
You can but I would not advise it. Purchase a new pump and you will then know for sure that after all the labor of installing the pump it will actually work, unlike a used pump from a wrecked vehicle which may not even work or may only work for a short time.
Where is the fuel pump fuse and relay on 1994 BMW 525i and how can I test to see why my fuel pump won't work
NO....if Fuel pump doesnt sent fuel to engine...engine cannot combust...
The pump could be defective. Or the power may not be getting to the pump. Check the pump fuse and relay to start with.