first off, make sure your bled well. might need to bleed the inj lines
at the inj while cranking. this is part of yer problem. now your problem
might be done as you did the glow plugs and the filters at the same time.
one thing that is forgotten is the fuel pressure in the fuel pump side.
the spring in the check valve controls this and gets weak. take it out and stretch it to about 22mm or so.
also forgotten is that the engine should spin purty good. if it struggling
then you need to check yer power and ground circuits. if ok then yer
starter just might be old and needing replacement. if draw is near 400 amps then its replacement time. fast engine rotation is a must during
cold starting times. needs to spin like it means it.

george