Discovery fuel pump

Hi there my discovery 2 td5 well I think its the fuel pump that is making a buzzing sound for like 30 seconds when the ignition is switched on, its coming from arround the reer driverside.

it was just one nick above the red and it wouldent have pulled up a slight hill in 3rd gear. then I filled it almost full and its going really well now.

what could be wrong with it ?

i would remove /clean filter housing especially one way valve and restrictor,in pipe connectors ,making sure you remember which pipe fits where,fuel pump may have just been trying to suck fuel from empty tank or might be a sign its failing,

and make ABSOLUTELY SURE there isn't a small O-ring trapped on the filter head when you replace the filter.

You need ONE large O-ring and ONE small O-ring.

The filter head has a bad habit of retaining the smaller o-ring, and then you end up with two.

This stops the filter from seating properly+.