Two questions. First. Is the fuel supplied from below the lift pump or from above the lift (priming) pump? Bleed the system to the injectors then if there is a miniscule hole or seal leak, it will pull in air and diesels don't run on air alone (ah, if only!). This can be checked by setting up a jerry rig from a fuel container that is above the engine and bypasses everything up to the lift pump. If it runs OK then you have an air leak. Fix it.
Second. On many rotary injector pumps, the pump is cooled and lubricated by running excess fuel through the pump. On many Bosch injector pumps this can be seen because any return fuel from the injectors (usually a small diameter tube) joins a larger diameter (usually about quarter inch) return line for the injector cooling/lubricating excess fuel. This larger diameter return is usually on top of the rotary injector pump
(there are variations ).
Sometimes, a small rubber seal inside the pump breaks and blocks the outlet causing a build up of fuel pressure inside the injector pump
. This will cause the injector pump to stop delivering fuel to the injectors. There are two ways to check this. Examine the fuel flow in the return fuel line from the pump. Minimal fuel returning indicates a blocked outlet inside the injector pump. Another method is to start the engine then quickly open the bleed nut on the side of the pump. Fuel should spill out quickly. Undo it enough to reduce any internal pressure build up, but not enough to starve the injectors. Not a permanent solution! Unfortunately a blocked pump usually means an injector pump overhaul
A plethora of filters and pumps can increase the chance of air being pulled in. Another issue is that if you have a pump for transferring fuel e.g. from tank to tank or through a filter, that pump may not leak when transferring as the fuel being pumped will help seal the shaft seal
(not that it matters here), however, if the pump is still in the fuel circuit when the engine is pulling in fuel, that end seal may allow air in. Solution is to "valve isolate" that pump from the normal engine fuel reticulation.
Best of luck.