300tdi LOUD tapping under acceleration

Evening all,
Having finally got my Defender back on the road, after a full engine rebuild, new clutch and gearbox, I have discovered a very loud tapping, but only when the throttle is more than around 75% open. This is in every gear, regardless of speed, but there is no smoke and it doesn't appear to be lacking power.

I've searched and found similar symptoms have need caused by a faulty brake vacuum pump, but my brakes feel fine and I'm really not sure that a vacuum pump could be so loud?

Injection pump, maybe? I did have to take the cover off to empty a load of oil out, but I don't think I broke anything in the process!

Any thoughts gratefully received!

Any leaks in the high pressure fuel system can sound like metallic tapping.

boguing said:

Any leaks in the high pressure fuel system can sound like metallic tapping.

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That's interesting, thank you. I will have a poke around and see if I can find any signs of a leak.

Have you double checked your fuel pump timing (with the correct timing pins)?

check that your exhaust manifold ist leaking between it and the head as this will cause tapping noise had this problem on our 300tdi disco as the gasket had gone

On my 300Tdi (Disco) this was a broken exhaust manifold stud, the one closest to the bulkhead ..

On my disco it was the vacum pump. I wasn't convinced until I used a long screw driver held to my ear and it sounded like a can of nuts being shaken around.