Sluggish pulling away? No top end power? This may help

I recently bought a new 300 tdi discovery manual. I have had a few now and they are all a bit sluggish off the mark. But this one was particularly sluggish, no get up and go, almost stalling through mud and rivers and hills in even 1st gear. Mpg was ok at 30mpg average. Top end was non existant even with the turbo at full chat. After a full service and checking all the usual suspects, i decided to remove the lift pump to check its operation. I was under the impression that if it had failed, the 300 wouldnt start. Actualy, it turns out that the rotary pump will pull fuel through both fuel filters and a failed fuel pump if it is healthy.

The upside is that the 300 will get you about day to day, even towing if you work the engine hard as i have done. The downside is that the fuel drag retards the pump slightly, both timing and fuel delivery.

So i fitted a delphi lift pump (noted to be the best) and it has totaly transformed my faithful old girl, off idle pick up is totaly different, in gear pull is miles better and top end is a lot smoother and easier to maintain rpm over terrain and hills.
Idle smoothness is also notably better. I cant comment on mpg yet but sn improvment is expected.

I hope this helps somone scratching thier head over a similar issue.

Forgot to mention that the old pump had virtualy no resistance on both cam and prime levers. The suction and blow though on the pipes was also non existant.

Have been driving now for a few days and the engine feels totaly different. I know this may be obvious to some, but worth looking at if you dont know the history of your own pump.