gt tdi won't start

[Agreeable Slick]

if the key has lost its coding, the immobiliser light will stay on and the display a message saying immob. active or something similar

Not the key. ECU as it was completely powerless. Not sure if ECU immo code is hard coded or not.

[bridgeking]

i have all lights on as normal and go uot as normal when turn key ,there is no light on and no message
golf is a 115 gt tdi 98

[bridgeking]

x

[bridgeking]

the glow plug light comes on and goes out as normal ,there is no light on or message for immobiliers ,its a 98 golf gt tdi 110

[bridgeking]

do the glow plug light come on with the ignition? if not it might be relay 109, which is behind the removal panel to the right and down of the steering wheel
are there any unusual lights lit up on the cluster?
also is it a pd or non pd version?

it comes on and goes out as normal

[EsSeX dAn]

right, ok. open the bonnet, when you put tge ignition on can you hear a click coming from the fuel pump? if yes thats normal, its the fuel cut valve opening. if not theres a problem there.
take out the glow plugs and turn it over to see if it squirts diesel out the glow plug holes. if yes itll be something else.
your best to get it fault code read to see if theres anything electrical gone wild.
my 110 went nuts a few months ago, turns out the timing belt tensioner puked up and lost the tension on the fuel pump, so it was getting the fuel, just at the wrong time!