Here’s the deal: Allis chalmers 6060 4 cylinder diesel. Fuel tank is above engine, gravity fed no tank fuel pump. I ran it out of fuel by accident - no problem filled it up, bled the fuel lines and filter all the way to the injector pump and it started a little rough, smoothed out and ran for 10 minutes fine. Then it slowly lost power and RPM’s and stalled out. From then on it starts and runs briefly before idling down and stalling on its own. The longer it sits the longer it will run before idling down and out. OK… starving for fuel so I checked and cleaned every line and fitting from the tank through the filter and to the injector pump including the bleed fitting at the injector pump and a new fuel filter. No change - it will start, rev up to full throttle, then slowly RPM down until it stalls. The longer you let it sit in between the longer it will run at high RPM before idling down to a stall - but only up to a few minutes max. I don’t know much about injector pumps, but maybe air in there and it’s not priming correctly?
