Hi,
Check for any signs of fuel leaks around the injector leak off flexible pipes and fuel dampness along the pipes themselves. if fuel present at the pipe ends and on top of the injectors change the leakoff flexibles.
Any good motor factor should have leak off pipe in stock.
What happens when the engine is shut down for several hours, where fuel leaks out when running, air is drawn back into injector when standing, hence air in injector which has to be cleared. The initial priming of the low pressue side when switching on has no effect on the high pressure side of the fuel system.
I know this works becuase I`ve done it on my 2.5 and other diesels.
This problem is usually found on high mileage engines with original flexibles.
The repair is cheap and the fix is quick. Approx 30 mins.
The pipes pull off and push on . All thats required is a length of pipe, a cutting knife and 13mm spanner to release a pipe bracket on top of engine to give better access to flexibles.
All the above of course only if the pipes are leaking. I`m not discounting dicky heater plugs, just offering a suggestion.
Hope this helps.
.
Plodder.