I have a diesel mower with a simple, old diesel motor, TUD5.

I bought the machine not running.

I have changed out the motor as old one had no compression. ( 4000hrs )

The new motor has 66000km and is as should be.

Compression.400+ on all cylinders.

The timing belt,water pump ,shims fluids etc all new.

The timing is 100% as should be.

The motor starts super easy and revs with no load.

It is super smooth ( for an old diesel )

The pump ( lucas CAV DPC from the new motor ) was sent off to a specialist to set up but i have a feeling it came back set up for a car and not the mower as the tick over was low ( mower spec states 1500.) and high end was set at 4000+ ( mower should be at 2650 )

I have changed out the new pump top section ( linkages, governor plate, metering springs etc.) from the original pump and it now revs perfectally between the limits (1500 and 2650 )

When I rev the motor to 2650 and load the motor with the hydraulic pump for the mower the revs drop to idle ( 1500 ) and wont build back to 2650.

If i move the throttle lever forward the revs stay the same ( 1500 ish ) although the noise changes slightly ( i think less clatter the more i advance the throttle ) but no change in revs.

If i cut the load it runs again as should. Revs freely etc.

I am sure that the pump is not set correctly.

Is there an easy way to increase the output pressure ( more fuel ) with these old CAV DPC type pumps or is it back to the specialist. ?

I found that if limited a little the return flow from the pump to the fuel tank it will rev up to 2650 and run perfectly under load but i am scared the this will push out a seal as there is defiantly too much pressure in the casing.

This tells me that the load is not too high ( faulty ) and i know max torque should be at 2200rmp on these motors not the 1500 it sits at.

Any thoughts from you guys with CAV roto pump knowledge

Thanks

Simon.