thanks for interest martin/john, you were both bang on, chain jumped. a bit of confusion with ad. they say supply 5v its 12v via ecm relay ( will light a testlamp) supply colour code grn/white ad greyviolet went back to beginning& sensor switching, removed inspection for pump & chain loose (how easy). think mecomic looked at mileage & thought to low for chain to jump without testing thanks for thinking any ideas time for this job cheers