We have a 2001 Focus 1.6 Zetec Auto. I bought it as a short-term runabout whilst in the UK but was so good that we brought it back to Romania where it is used on mainly unsurfaced roads.  Once in a while the engine cuts out and will not restart. The engine tries to start but cuts out immediately. Fiddling with various parts of the wiring seems to fix it, at least for a while. The engine fault light comes on with the other dashboard lights when the key is turned on but it stays on until the engine starts, then goes out - my recollection is that it should go out at the same time as the other lights.  My scanner shows that no diagnostic codes have been recorded but wiping the codes anyway seems to resolve the problem for a while.  Curiously, the problem seems to occur after the vehicle has been pressure-washed. The nearest official Ford dealer is a 7-hour return drive so I'm hoping that it is something relatively simple!

Id focus on that wiring loom you fiddled with to get it working, trace the wires from origin to destination and try work out what is causing it.  if you have a multi meter you could run a continuity test on all the wires, if that doesn't lead to any results, try a resistance check, searching for wires with particularly high resistance. if you dont have a multi meter then unwrap that loom and check the wires, your looking for breaks or discoloured sections, typically swollen with a white bleached look or a covered in a green dust, your looking for problems with the termination of the wires or water damaged plugs, unplug and look for white / green dust around the pins. 

You really need a multimeter to do it right. 

you mentioned washing the car causes it, check for water ingress where is shouldnt be, particularly around the PCM, GEM, fuses and electrical plugs .

its a needle in a haystack, you need to narrow it down 🙂

Thank you for the advice. I do have a multimeter and some experience of auto-electics in older vehicles (I've owned Land Rovers since 1971!) so that gives me a clue as to which side of the haystack to start from.