300tdi not starting

morning got a 97 300tdi disco had a problem 4 weeks ago started with loss of power then engine would not start just turning over got diesel to injector pump but no fuel to injectors changed fuel filter new cam belt and replaced injector pump. motor started no problem ran ok for a couple of weeks then stalled started straight away but stalled again now engine just turns over. first time this happened it would either run on after i turned it off or stall but would fire up straight away have i been unlucky with second pump or could this be an electrical fault. any suggestions would be appreciated as not too happy if i need to shell out for another pump. thanks john

I've had this myself on two pumps and on both it was the black box on the back of the pump not activating the fuel cut off solenoid. Problem is that it's held on with two tamper proof bolts, so to get it off without causing damage, you'll need to remove the pump to get access with a drill/chisel or whatever you decide to use to remove them.

Is the wire on the back of the pump connected with a good contact?