Oh yeah, and if you feel like using ether ("starting fluid"), forget it. It will probably destroy your glow plugs. Even if it does manage to get your truck running, it is very bad on the upper cylinders, valves, turbos, etc. It is very "dry" which means that it lacks any type of lubricative properties at all.
On a hot engine, it won't work at all anyway. The heat vaporizes the ether, and makes it even harder to turn over than with out it.
On the ambulances I work on, they have (or had until I got a hold of them) resonating chambers on their intakes. If you use ether, the ether builds up vapors in the chambers and when the engine backfires it blows them all to hell. There will be pieces of brittle "Bakelite" plastic all over the top of the engine, on the ground, in your eyes/teeth. It's really cool.
So,
Diesel rule #3: Don't use ether. Use a gasoline soaked rag to hep you start a stubborn engine.
Also, DW40 will work in a pinch too. I don't think it is the liquid part of the WD40, I think it is the gas propellant in the cans that is flammable, but it does work.