Hard Starting when warm

[T.C.Mac]

A little input?

I have a 1998 6.5 TD with so far a unique issue. When the truck is stone cold or hot, (withen 5 minutes of being shut off ) it starts right up. inbetween times it starts but needs to crank for at least 45 seconds before it will fire. I have replaced the controller, all the glow plugs ( with the AC60G's )and the thermal sensor in the thermostat housing. When stone cold the plugs seem to energize for approx 8 to 10 seconds and it fires right up, after about 15 minutes of being shut off the plugs only energize for about 5 seconds or less.
It seems like the PCM may be sending the wrong signal to the controller telling it the engine is still hot when it is not? Is there another sensor that may be bad giving the PCM the wrong data? any help would be greatly appreciated. Mac