Runs but no power and no rpms (6.9 litre}

[fishingheron]

Motor was idling poorly. Return lines were replaced along with all clamps. The fuel filter and the fuel water separator were replaced. There seems to be no air in the lines.
Starts fine but rpms drop. Will not go above 1300 rpm. Is this an injector pump or is there something else I can try?

 

[icanfixall]

Did you remove the injection pump from the motor when you did this fuel system work?

 

[fishingheron]

No I did not remove the injection pump.

 

[Joe Mc]

Could be the lift pump. Check the fuel pressure at the schrader valve on the filter-head, should be around 6 psi. There is also a flow test you can do at the valve, but I can't recall the numbers and I can't find the test in my ford manual.