TD4 Lift Pump

Have done a search and it appears that this pump can be unreliable. Mine sometimes fails to run (no hum when ign on) and then obvs will not start. Has anyone found any causes other than the pump? Feed, relay, connections etc??

I have cleaned relay contacts, cleaned pump connector and will attach a test lamp to it and leave it fitted awaiting the next failure, but if anyone can point a similar fault then great ! My car has never stopped once it is running and so I am thinking it is NOT the pump.

Thanks, Andrew

What year, model, engine?
Is it when trying on the ignition it just won't fire up? List the symptons