Use pressure guage at the fuel manifold. Test 1 - Check non return valve 1. Connect a pressure guage at the fuel manifold. 2. Turn the ignition to position 2.The fuel pump should run for 5 seconds. Turn ignition to zero position 3. check the fuel pressure is about 3 bars. 4. Go for a ciggie and come back after 30 minutes. 5. check the fuel pressure is maintained or dropped slightly. If dropped more than 1 bar, then fuel pump is faulty. Test 2 - Check fuel flow 1. Do step 1 2. Start engine. 3. Check pressure 4. Rev engine to 3000 rpm 5. check the fuel pressure is around 3 bars. If pressure dipped too much, pump is weak.