Mate`s got a Cav TD (Isuzu engine) which won`t start. Sounds very much to me like a fuel pump problem. Sorry it`s not a BX but the reason I`m asking for advice on this forum is that I wondered if the advice I got to check on any diesel engine fuel problems was this, and assumed it may apply to BX`s as well?
I was told if the main fuel line between injector pump and engine was removed at the pump end then that end could be submerged in diesel and then attempt to fire up engine. If engine started then died off after fuel had gone then that would indicitate injectore pump trouble.
Please bear in mind I heard this info quite a while back and I`ve slept and

since then so may have it hopelessly wrong

Vauxhall apologist.