Replacing glow plugs and injectors.
 

I've got a service record that came with the truck; it was used as a welding rig.

The GP's were replaced about 35,000 miles ago.

Injectors haven't been touched.

The truck was maintained properly up to 100,000 when it was sold to the second owner. 30,000 miles later, I'm let to clean up what owner number 2 messed up.

Question is: should GPs be replaced on a regular basis, or as needed? Same with injectors.

I just feel that the truck doesn't run as it should.

gp should be replaced as they fail. injecotrs should be replaced as a matched set. if it never had injectors, it is time.

Thanks for the info!

only use motorcraft beru GPs. do not use autocraps or anything else or you will be kickin yourself in the ass when one swells up and gets stuck in the head.

I use Glow Plugs from this site. Glow Plug - Ford 6.9 L IDI (Spade Terminal)
Truck starts on a half crank even in single digits. They also make good injectors and lines.