There should be a very definite suction on the inlet side, when you have the pump in your hand and you are moving the lever.
Are you sure that the lever is sitting on top of the camshaft not underneath it?
If it is above the cam, then there must be a problem either with the two valves, or the diaphragm. If you can find a kit for it, replacing all three should solve the problem.
Or; the fuel pipe connections are leaking air, or it has run out of fuel,
Cheers Charlie