My newly overhauled 4.2 injected series 3 engine has a rattle or knock that sounds to be coming from the sump. The rattle does not sound consistent with every rotation. Any suggestions of what it could be

 

Pure guess work.

Oil pump pipes not secured properly.

The catch can thing the pick up poipe sits into is misaligned, or insecure.

The front pulley BIG bolt is not tight enough.

Either or, the 1st 2, will require the sump to come off to find and sort.