Fast and dirty temp fixes.........
Easy Start is brutal, it can knock the stuffing out of an engine in no time. make sure the inlet and exhaust are not fouled up and then use WD 40 or 3 in 1 oil aerosol spray, or similar.
Easy start works by lowering the compression ignition point but strips the oil from the bore, and reduces the compression, an aerosol spray oil helps the seal thus and raises the temperature in the chamber, at TDC, allowing the diesel to light off as it should, as well as providing extra fuel.
A 'Camping Gaz' type blow lamp (Lit. obviuosly!) directed down the air inlet, whilst cranking, will warm the charge air, and the compression will have less work to do to get the temperature in the chamber up to point where the diesel will ignite.
Using decent quality road diesel, rather than 'Red' will help too.
Ask me how I know how much wear 'Angels Breath' can occasion to the bottom end of a well knackered diesel!
None of this is better than a proper overhaul, but it might help get you through the season, with enough of a motor left to rebuild!
Cheers Stef