If cleaning the pump suction strainer does
not correct the trouble, isolate the pump and relief valve from the
rest of the circuit by disconnecting at point E so that only the pump,
relief valve, and pressure gauge remain in the pump circuit. Cap or plug
both ends of the plumbing which was disconnected. The pump is now deadheaded
into the relief valve.
Start the pump and watch for pressure build-up on
the gauge while tightening the adjustment on the relief valve. If full
pressure can be developed, obviously the pump and relief valve are operating
correctly, and the trouble is to be found further down the line. If full pressure
cannot be developed in this test, continue with Step 3.