Stanadyne no longer makes this pump so rebuilt is all that are available.
Seals and gaskets are made by various manufacturers, most seem to last at least 10 years. The supply chain has not been contaminated by knock off suppliers. Rubber compounding is still a tightly controlled trade secret and crucial for long life seals.
Aside from the governor weight cage drive ring on pre 1985 pumps, the first seals to leak are the throttle shaft. Originals last at least 25 years. These can be swapped without pump overhaul, only one critical adjustment with the low throttle timing advance cam.
Stanadyne certified rebuilt units are equal to new. DCP, Badger and Oregon Fuel Injection all are quality rebuilders which calibrate to the data plate specifications.
These pumps are precision built high pressure devices which are the sole component of power control in the engine. They are equivalent to a gas engine carburetor, distributor and points of a traditional 1960s engine. Built like a watch coupled with a high pressure hydraulic system.
Diesel fuel has changed considerably, the most change is the addition of fatty acid methyl ester, biodiesel, to most road diesel. This reduces shelf life and complicates water contamination.
