Focus Diesel 1.8L

• Manual transmission
• 152,000 miles

usually, when you turn the key one notch, all the lights come on. Once the coil is warm enough (this is a diesel car!), all the lights go off. You turn the key another notch and engine starts and away you go. Over past few months, turn the key, all the lights come on, then all the lights EXCEPT the coil go off. the electronic reader effort (where the miles travelled is indicated) shows up as a horizontal line. Engine wont turn over.

Occasionally, after twenty or thirty turns of the key. Engine does start, only to cut out without warning after as much as 35 miles, sometimes immediately, sometimes have no problems at all!
This time, it is stuck for good.

Previously, it has gone to Ford to be put onto their electronic computer reader which shows clearly no problems at all. My mechanic, began painstakingly to inspect every wire, came across two frayed wires - one connected to the ignition and the other to the clock, which may well have been touching now and then. Insulated those, car started no problem. Thought that was the problem, now solved. Five days of no problems and last night it refused to turn over. Again!

At my wits end. Any suggestions at all? Can't afford another car!