2001 Landy Disco

I have had an intermittent issue with my Disco being really difficult to start and sometimes like now just refusing to start completely.

Ongoing since last September. Was never ever a problem before. Engine turns over, starts to catch, sometimes does and sometimes doesn't. Random with very little explanation.

New starting motor, new glow plugs, new fuel pump. Problem remains the same.

3 different mechanics including a Landy specialist. No-one can find an explanation for it.

Worse in cold weather. Always starts fine at the mechanics and becomes problematic and lumpy or refuses to start when returned to me.

Immobiliser system giving trouble not allowing engine to start even though it turns over?

Injector seals need replacing? Fuel pressure regulator on its way out?

Wild guesses on my part but it may give some pointers.

Battery ?

Good point - I was assuming it still tunred over OK

Fuel filter housing
You won't be able to see a fault with this , it's just a case of buy one , fit it and see..
Oh and put a premium brand filter, like fram or Mann , pay over £6 for one
I've fixed two td5s with the exact fault you describe this way.

Check the battery, it must be A1 condition on a disco because of all the electrics. If its intermittent, it could be beacause your use is intermittent, use every day starts fine, leave it for a week and the battery will not be up to the job.