I have the W38B- 4, which is very similar to your W42B and I would say you need the Faucet lift pump. It is a 2 pipe system, supply and return and is designed to pump back the un used fuel. Are you sure it is not pumping? When I turn my key on and them press the glow plug
button I here a bunch of fast clicking then it slows, then hit the start button and she fires right up. Once it fires I think the pump will stay on.
I'm also looking for a serpentine pulley kit for my engine. Same pulleys as yours.