Nightmare diesal solenoid

Had trouble getting my car to start, cleaned solenoid, worked fine for a while then started acting up again so got a new solenoid, worked great for a while, now it's at it again, took it out again and there was little iron fileings on it. Is there anything I can do to stop this??? I'm getting fed up of hitting the solenoid with a spanner!!!!!!! Cheers

I suspect injector pump failure is imminent.