Fuel lifter pump stays on with key off

[wefreed]

My fuel lifter pump remains on after the engine is shut down and the key is off and removed. I have to reinsert key and turn to glow plug position (#2 which also energizes the fuel lift pump). Next switch it off without starting the engine and the fuel lift pump remains off. I suspect a problem with the oil pressure switch which was replaced 12 months ago. It too supplies power to the fuel pump when the engine is running.