May be the tachometer fault . If it as a short it will stop the pump so the car will stall .Re start and run again just to repeat again. Remove connection on the rear of tachometer and if it runs ok replace the tacho. But i would do all the usual things first . This is a last resort . Check all fuses .Put a little grease on the tip of every fuse and remove it after.Check also all earth points ,remove them, clean up conntact points on the body grease them also then refit. Let us know how you get on .