Starting issues on 806 HDi

Has anyone any suggestion on the following problem. My 806 HDi will not
start. Having checked everything all seems OK. I then sprayed a small
amount of oil into the air intake and the engine started and ran fine.
Even when the engine was hot, once stopped it would not start until I
sprayed oil into the air intake!!!
Any clues or help would be appreciated.
My local dealer has suggested a problem with the diesel injectors and has
quoted a huge sum. I cannot see how it could be the injectors if the
engine runs OK???

 

Air in fuel system, low cylinder compressions. injection pump timing incorrect, this is what a haynes says about a engine difficult to start when hot,(missed one) air filter element dirty or clogged.
from chris Addlestone Surrey

 

I would guess at this being the priming pump in the fuel tank.

When you turn the ignition on, you should hear a short buzz of about 5
seconds, this is the fuel system priming up ready.

If this pump does not prime the car will nor start.

The failure of the priming pump is a common problem for all of the HDI
engined cars, try turning on the ignition then laying down under the
car and give the bottem of the fuel tank a good hard slap, sometimes
this alone will get it to prime, but usually only to fail again next
time!!

Regards
Slim