My L345's can be hard to start cold. If battery, glow plugs, and the decompression linkage are all in working order it will eventually fire after some black smoking. The glow plugs remain energized while the starter is running, making a strong battery and good connections essential to cold-weather happiness.
Radiator hose heaters help somewhat but the closed thermostat limits block circulation. A freeze-plug heater works best. On engines without a threaded hole, a tapered adapter is installed in a tapered freeze plug hole. The hole has to be dry and really clean. The adapter is lightly hammered in place, using Loctite sealant.
FWIW neither of my L345DT's ever had a heater - but they've needed new compression release cables.
A loader search for these can take a while - I finally
adapted one not intended for it
Take care, Dick B.