Fuel Pump Solenoid

Hi

I looking for some advise. I just want the correct job done,

I have lost the power on my 54 plate Diesel Octavia. I took it to garage 1 and they told me the fuel pump had a problem. Somebody else said the timing could be out on the fuel pump, I have had it replaced the timeing belt recently. I took it back to garage 2 they checked timing and said it was ok. I have now taken it to a turbo specialist he said that the fuel pump solenoid has gone? can somebody tell me if there is such a thing? I have seen a relay solenoid but not a fuel pump solenoid. The engine at the moment sounds like an old comer diesel and when you rev it up black smoke comes out of exhaust. thanks in aniticpation.