6.9 idi only idle at full throttle

[ford401]

I have this 6.9 in an old IH farm truck. was running fine then out of the blue it will only run when throttle is wide open. It just sits and idles even tho throttle is pegged. see video; all new fuel return lines, clear line off the filter return showing no air in system. check valve on top of pump was removed and cleaned. new fuel pump, new filters. any ideas?

 

[KansasIDI]

Your video didn’t show up…

 

[Clb]

Linkage?
Ip shot?
Details man.

 

[Nero]

Make sure the return on the injection pump isn't plugged. Pull the 90° elbow off, then pull that next fitting off.

 

[FrozenMerc]

The Injection pump may be internally worn out. There is so much internal leakage past the pump pistons that it takes full stroke to generate enough flow to the injectors to keep the engine running at even just idle speed. Like Nero suggested, check the pump return line, if a bunch of fluid is flowing out with the truck running, it is likely the pump is toast internally.