So i have a 1986 chevy c30 with a 6.2 j code, the injection pump had the elastic ring failure in the injection pump and i rebuilt the pump using the new solid weight cage. Ever since the rebuild it will run for minutes, sometimes seconds, or even hours but eventually it will run out of power and die. during my diagnosis i have so far determined that fuel supply is good and steady, Im using a carter electric pump with a 5 micron water separating pre-filter and a 2 micron cat post filter. The post filter head is mounted to the firewall a few feet from the injection pump and has a valve to open air on the outlet side used as an air bleed or in this case to diagnose/determine fuel pressure or volume. When you pull the return line from the top of the pump it will return large amounts of fuel when its running good, and once its running poorly it immediately changes to a dribble. Sometimes the idle will surge, in this instance fuel return volume surges right along side of the rpm surge. but at all times, fuel feed is steady, air free(as best i can tell) and more then sufficient volume and pressure. My testing is based on me opening the air bleed and watching it fill a water bottle.

I have read about the return check ball being a problem, but when i remove it all together and run the motor with fuel free flowing it is still doing exactly the same thing... maybe this is a useless test as i am relieving any pressure that should stay in the injection pump? After rebuilding the injection pump the truck would hardly run on the mechanical pump(which was verified good in volume testing), swapping to the electric pump has given it a lot more power for short bursts and overall its running better and more often but still very un-derivable, leading me to believe the transfer pump in the injection pump may be to blame as i'm helping or band-aiding so to speak transfer pressure with the electric pump? just some thoughts, im completely lost here, idk if i should pull the transfer pump apart or pull the whole thing back apart.