My 1997 3500 6.5 Diesel has become impossible to start since winter arrived without being plugged in. Plugged in to the block heater and oil pan heater, it starts OK. My thoughts are...glow plugs or injectors? Any thoughts......

And it also has little heat from the heater. I replaced both thermostats in the cooling system less than a year ago because I thought that might be the cause, but it has only gotten worse, or so it seems. Any more thoughts.....


Thanks

oh oh unless your heater core is plugged you might have a bad head gasket/head crack

try backflushing the heater core, to remove any crap that can be built up in there.
As for the hard starting problem, if it is firing smoothly, running on all cylinders, check the glow plugs, and glow plug relay. Also, as a side note, check the fuel lift pump on the inside of the left framrail, under the drivers door. that pump going bad can cause hard starting problems as well, in both cold and warm weather.