300 tdi won't turn over

Ok, I've looked at a lot of the threads on here. My 1996 has suddenly decided to not start on the key. I've put a brand new starter motor in it, and charged the battery so it's not either of those. It's not a seized alternator as I've checked that

I think it's got something to do with the immobiliser, which again is odd as it's been fine for the last year. I bought it last January with no key fob just a key to get in and a separate one to start it. It's always flashed the indicators momentarily but always started

I have seen a thread suggesting it could be this. Has anyone got any pics to show me what I need to over-ride and how and where I go about sorting it out

I will be testing the power going to the starter tomorrow so I think that just leaves the immobiliser

Appreciate any assistance

The engine not cranking is a sign that the engine is immobilised but your disco would normally have a fob to remobilise the engine, as u don't have a fob suggest the immobiliser spider has already been bypassed.

So what ever was used to bypass the immobiliser spider or the ignition switch to starter motor circuit needs checking.

Basics first, check the earth by putting a jump lead between battery negative and engine block, check you have 12v to the spade connection on the solenoid on ignition position 3

So it's the spade end terminal of the solenoid, not the other connection with the nut? Sorry, but first time doing this. So, if I run a 12v wire to this from the battery will it turn the starter motor and in turn the engine. It's a new starter motor. Assuming this works, what's the peHi, can u guarantee these are 100% authentic Oakley? Thanksrmanent fix. Thanks

Sorry, god knows what that last bit of text is about. Assuming running a +ve feed to the spade terminal starts the engine what's the permanent fix?

Assuming a 300 starter is the same as a 200 there is a thin wire that connects to a spade on the engine side of the solenoid (from ignition switch). It activates the solenoid, like the feed to a relay and bad connection there is a common issue. If everything else is ok then a direct feed from battery to spade will turn the starter constantly.
Other likely problems are ignition switch (check for 12v at spade on solenoid at ignition position 3) but more often than not its a bad earth from battery to chassis and/or chassis to gearbox. Always worth connecting a jump lead from battery -ve to engine to check.

I've removed both the earth Leeds, battery and starter, cleaned and rebolted. Will try the other bits tomorrow and revert, thank you thus far

All sorted guys, thanks for your help. The chap who had it before put a fused wire in to bypass the immobiliser. on chasing the positive back from the starter, bloody fuse had blown.