200tdi fuel shut off

Help!
I have replaced the fuel shut off valve 3 times in less than 2 years.
The engine shut off or lack of engine shut off is back again.
I took thr latest one out gave it a shake and a tap and reinstalled and it worked 2-3 more times and it went back to old problem(not working).
I have removed the wire to the valve and it still does not operate.
So it is not electricial.
Dies any one have a solution,please?
American John

American John? Thats a toilet innit?

I'm assuming by 'fuel shut off valve' you mean the 'stop solenoid' ? If so, they're only about a tenner... fit a new one

the problem is that I fit a new one about every 3 months