diesel 4x6 starts and idles, bogs down when throttle opened

difficult to start, idles fairly smoothly when throttle is opened bogs down even in neutral checked air flow, fuel filter, lift pump, screen in fuel tank and fuel
lines prime lever on lift pump produces fuel at injector pump, about an ounce for five or six pumps how can I check operation of injector pump and injectors ? or can you suggest another possible cause I am unaware of?
these critters are new to me and I need all the help I can get thanks for your response