On my one it was the detent units, they are screwed into the remote shift unit and have spring loaded balls, these can and do faill with time, I replaced by removing the centre consol and remote shift cover but shreaded all my fingers in the process, it woukd have been much easier to lower the rear of the gearbox a little, unless you have experiance I suggest you have someone do it for you.
Sorry missed your post! (baccardi)
Truly is a surprise if it's was a genuine L/R part but that could be the "sods law" effect, if the in-tank pump is noisy it's in trouble and might not pump with conviction.
I bought one from a well known internet department which was a genuine part except that it wasnt :-(
Maybe already though about but, is there any chuffing from the oil filer, what would happen if the front seal in the injection pump was shot, thats been seen before.
The recommended proceedure can take a few attempts,
Your in tank (lift pump) could be faulty and could be the reason for other issues,can you hear it running.
Had the same last year, the clutch fork on the P38 Diesel is a two peice unit held together by silly little roll pins, the pins wear and snap causing the contents of the slave cylinder to run away in fear, all the fluid will have left home as well.
Unfortunatly it means removing either the gearbox or engine, I've always removed the engine.
Roll pins are cheap but the job will take a while, if you replace them with normal pins push smaller ones inside to give a little more beef.
It does sound as if you have a faulty relay but---Are you checking the glow plugs voltage when the engine is cold as the on time is reduced as the enging warms up, when hot you might not even get a blink.
Any difference in starting cold or hot that could point you in the right direction.
Any bubles in the clear fuel pipe at the injection pump.
You tried another battery, any chance that both were low, and the cranking speed is slow, starters can wear without the owner being aware then the cranking speed is simply not fast enough to fire up.
Maybe a little mor detail on the symptoms and effect of the fault would help.