Shut it off at end of day, next day wont start?  Electric start, no pony, no glow plugs.  So what would be the next thing to check, fuel flow?  Injectors?  Pump?  any advice welcome and thanks.  Tom

Bummer. I wonder if you lost “prime” and fuel bled off?
I would check fuel supply to pump, and crack open the tower vent while spinning on decompression mode.
If you’re in a huge rush maybe a sniff of canned goods?
If you’re in a pinch, you know where some are available to borrow. Good luck. JM

How long since fuel filters changed. Check for fuel in engine oil.

Why not just crack the injection lines and hit the starter a few revs. If no fuel showing take it from there.

You did not say but sounds like it was converted from pony start, does it still have decompression lever? Someone messing with it maybe.

I have D6 that if it sites it needs to be bleed to start, so that is always something to check.

simple things first.
does it wind over.
has the fuel gelled due to cold.
is it getting fuel if you see white smoke from the exhuast its getting fuel then the question is, is it fuelling properly or is there a restriction in the air cleaner/intake.
is it decompressed or not. they wont fire is decompressed you will get fuel smoke though.
is it too cold.
have you got the throttle wide open to give full fuel some machines need full or 3/4 throttle to start easily particularly in colder weather.
bleed the fuel tower and injectors.
has some numpty turned the fuel tank tap off. we have a stationary engine that doesnt like it if the tap is turned off it gets a massive airlock and is a pain to bleed as its hand cranked.

when did it last have a set of fuel filters? have they plugged.

avoid using aero-start(ether) often once you start using it all the time you need to use it all the time. it is hard on a engine.

Got it! The fuel filters were changed about 6 hours run time back. I opened the bleed at the fuel tower, and it leaked diesel, so moved on to crack a injector, it bled when I turned the engine over, so it has fuel, put it back into compression set the throttle to 3/4, a tiny shot of E and it fired off, ran well all day. Thank everyone for thier kind advice, very helpful. And yes it is a pony conversion and has a grader motor fuel system and a turbo, was like that when I purchased it a few years back.

that is a advantage of the pilot start is you have oil pressure before starting you can still do that with direct start but need to decompress it first.