The fact it starts and runs tells you it's not the glow plugs...I had a similar problem with a 205 diesel...It started no problem, ran for about 15 seconds, and then cut out.
With only a great amount of priming the fuel, would it re-start...and then run perfectly for the rest of the day....the following morning I would go through the same sequenceof starting fine and then stopping.
Eventually I solved it, and what was happening was I had a slight air leak on the fuel filter housing.
This allowed air to enter the system, and let the fuel that was in the fuel line... drop bank into the tank. So no amount of turning the engine would lift the fuel back out of the tank and up to the filter....but priming would.
So the small amount of fuel that was held between the filter and the pump was running out after 15 seconds...after that it was drawing air.
Let us know if you sort it.....its another story about how I found the air leak.