wont start

well todays problem is this ,
ive just done the headgasket on the td5 discovery .
got it all finished and back together started it up and it ran like a dream , had a test ride and it sounded much quieter and ran smoother than before perfect i thought .
the next day (monday) the gf used it all day then a buzzer sounded but i think this was just the air suspension it still ran perfect and sounded good so the days driving over the car was parked up .
the next morning i went to car to go to work and it wouldnt start so after work i had a look , fuel pump working , changed fuel filter , looked for leaks , none , so pulled air inlet off and put wd40 down inlet and it will run on that but still wont start .
is there a valve in the fuel system that stops the fuel ? or is it the injectors that stop the fuel ?
im running out of ideas now so can anyone help ?
thanks carl ..

Did you check the fuse box? on my Defender 2003 Td5 I have a 100amp fuse which controls a large amount of functions, this can cause the vehicle not to start. Once sorted it fires up first time. Its the one that denotes the glow plugs.

Not sure if this helps?

Just

had a quick look at fuse box and all looked ok but will double check it .
im wondering now if its the fuel presure regulator ?
do they just pack up or break down over a period of time ?

1.Are u sure it's not immobilised?... is the red LED extinguished while u try to start the engine?

2. Check the crancshaft position sensor and it's plug/wiring ... it might have been disturbed when the head was removed and after a while it ceded somehow.

well still cant get it going so looking deeper .
is it true engine management light comes on if crank sensor fails ?
also now im gonna check pressure valve on back of head .
im wondering if the o ring has failed a long shot but running out of ideas .
if still no joy i will have to get it plugged in to computer , dont suppose anyone on here in leeds area has the toys to do this do they ?
well here i go again .....

U better plug it in before u do any damage www.discovery2.co.uk/ Nanocom Locator, get help from your Land Rover Buddies!!!