no link re - water system, there could well be " crud", in the metering head ?....but im coming back to the 5th injector, sure you have checked you have good ignition, the 5th would have spayed neat good fuel into manifold. a test for the 5th injector I would do...disconnect the ignition coil for safety, remove 5th with its pipe still on, pope in a safe container....crank the Cold engine...you MUST see a full high pressure spray. if not anything...get back to me for more tests advise , Peter