Hi i have a 1995psd 155,000 miles, I heard that a cause of smoking when cold is the o-rings on the injectors and worn out is this true ? Also i seem to have alot more Blow By then i had when i bought the truck 10,000 miles ago, can worn out o-rings cause Blow By ? Thanks for any help ?

 

The injector O-rings act as gaskets on the injector, separating oil, coolant, and fuel. If any of the O-rings fail, you would have cross contamination of fluids, unless it's the bottom O-ring, which would cause a loss in compression.
When my O-ring went bad, I had huge smoke issues, and the truck ran very weak, but mine was the bottom ring. If your smoke problem goes away after the truck warms up, I'd suspect something else to be the cause. Perhaps something in the glow plug system.
Incidentally, mine blew at 130,000 miles, so yours might be due for a change, if for no other reason than preventive maintenance.