So five weeks ago I was driving my 2011 Ford Focus diesel when the car lost all power and I got the message 'engine malfunction'. The mechanic ran the diagnostics and got the code P0088 which means high fuel pressure. He's done everything he can think of to fix this but can't work out what is causing it. He's changed the fuel pressure regulator and also the starter motor (not sure if that's related but even the tow truck driver said it was gone). The car will run with a tow start but it will not start up normally with the key. I think mechanic also said he can reduce the fuel pressure manually and the engine runs well, but still won't start on it's own.

Does anyone have any ideas what the problem could be? Any help would be much appreciated. 

You should have the fuel rail pressure checked by a diagnostics computer. Could be a faulty sensor(fuel rail pressure sensor) or the wiring to it.