6.9 fuel starving

[Donjr]

Hey all, my first post. I just bought a 85 f250 separator had been bypassed and new returns and injectors also( supposedly). I put new motorcraft glow plugs in, not fun getting swollen autolite out! but pb blast works wonders. My question is; it'll start and idle for hours but when I advance throttle it will surge and die as if air getting in, both fuel tanks are 3/4 full and I don't see any leaks, also put new fuel filter on, I'm thinking inj. pump although this one looks fairly new/rebuilt, any suggestions..... Thanks

 

[mexicanjoe]

youve probably got air intrusion. Check all your lines from the tanks to the filter....... something is probably loose.

 

[riphip]

Could also have a fuel pump/feed problem.