There is a mark on the flywheel and a pair of marks under the timing cover on the pump, however I agree that this does not sound like a pump problem.  It soundls like an air leak problem.  I would suggest taking a look at all the hoses up on the flow meter for datatronic above the front of the engine.  If they have not had real hose clamps installed in place of the springy ones, do so.   Also consider the stupid Lucas fuel filter.   

We fought with losing prime and losing power due to air for a long time on our MT635....hooking a hose direct from the fuel tank to the lift pump and bypassing all those leaks made the problem disappear.  We had leaks at all places I mentioned.  Took a while to work through them all.