HELP!! 88 Diesel wont Start!!

I am new to owning my 88 4x4, 4 spd 6.2 diesel. I purchased the truck in 04/2006. I thought that I remebered someone telling me prior my purchase that these older diesels can be an absolute pain starting in the colder weather. I have replaced both batteries, and that seems to have helped, but it is just near impossible to start. Any ideas? Thanks in advance.

Test your glowplugs with a testlamp. Put the testlamp on battery + and see if you have contact on each glowplug, take of the conector on each plug before you test. Another thing to check is the temp sensor on your right head right where your exaust is going down in the pipe... does this sensor open under 40 degrees celsius? this sensor turns the timing a bit and incres the idle when cold.