Short trip round town, engine normal temp, stop for 2 mins then it refuses to start.
Starter is cranking normally and the battery is fully charged. Yellow glo-plug heater light comes on with ignition as normal and goes out after 1min - but still no start. The engine's hot so shouldn't need pre-heat but tried it with pre-heat and also no pre-heat. 10 mins of tut-tutting and looking very hard at the engine it then starts at the turn of the key. 
Very frustrating.When home I checked the glo-plugs for 12v with pre-heat on and it was all ok. They went to 0v when the yellow light goes out too. I can't think it's anything to do with the pre-heat side of things as it's happened twice on a hot engine. Is the fuel cut-off solenoid suspect?
The fuel is getting there too as when I pulled off the return hose from injectors fuel leaked out.
The engine's in good condition too, good compression with little smoke. Have had Scooby for 5 years and it has always started brilliantly hot or cold.
I HATE ELECTRICAL SNAGS!!!
Oh, it's an AAZ 1.9 Td
