Truck Repair: 94 Chevy Blazer 6.5 Turbo Diesel, chevy blazer, glo plugs

Question
Hi,
I have a 94 6.5 Turbo Diesel. The problem is that once a day I will try and start the truck and it will turn over but not start, or it will start for 5-10 seconds and quit.  It does this at any time , warm or cold. It is not a jelling of the fuel, and when I let it sit for a few minutes and sometimes a day it will start again without any problems.  It has never quit once I am on the road.

Thanks,
John  

Answer
could be either an air leak in the fuel, an injector leaking fuel down, or bad glo plugs. when it does start does it sound good or stumble and cough? fuel filters both been serviced? there is a return filter orifice on the 6,2 that used to plug and do the same thing, was a threaded in spigot on the very top of the pump, not sure if yours has the same thing.