Fuel pumps

Get a couple of 5 foot hoses and attach one to the inlet side and one to the outlet side and get a can of gas. Drop the end from the inlet side into the gas and the one from the outlet into a clear container and crank the engine. You should see about a quart of gas pumped with about15 seconds of cranking. If that checks out OK, hook the car's supply line back up and try it again. If you lose pressure then, there is something wrong with the line going back or the pick up in the tank itself. If any of the metal line or rubber hose going back it porous at all, the pump will suck air instead of fuel.

Put a vacuum gauge on the inlet tube to see if it will draw from the tank. Don't expect real high vacuum, but there should be some. Pressure is harder to test if it is just pumping air. If there's fuel in the pump you should be able to get 3 - 5 pounds of pressure.

Besides pumping fuel, a ripped diaphragm can let fuel run into the crankcase. You'll see the oil level going up on the dipstick if fuel is entering the engine during extended cranking. Usually it will leak outside the pump too.