The Rover-Landers of BC

Anyone know how much fuel should be returning down the return spill pipe on a 300Tdi or 200Tdi? Mine presently shows no fuel returning during running in a clear pipe that I installed to check on this. Seems a little wrong. Return pipes themselves aren't clogged end to end of the circuit. Operationally injectors are too noisy and there seems to be a bit of a power lack. Not blowing air into the injector pump, no bubbling to be seen just nothing in the return line. ??? Any help here would be appreciated.

JD
Vic BC
MOD 110