Lost compression??

Hi All,
New to the site, hope you can help me diagnose a problem.

TD4 02

Symptoms:
White smoke on start up for about 10 seconds.
Settles down and clears. Although sometimes it does blow out unburned fuel at idle.
Idles OK.
White smoke at 2K - unburned fuel.
Compression 330 on pot 4.
Loud metallic click every 10-15 seconds at idle.
The click continues at a longer interval when the engine is switched off! For a long long time (got bored and cold sitting by it trying to find out how long)
Runs fine other than slightly less power.
Runs better in warm weather.

History:
Using Oil - No
Using water - No
Reconditioned injector fitted. (problem was much worse prior - erratic idle)
Rear fuel pump fitted.
Several 'cleaners' added to fuel over several months. Runs better with the additive in, however doesn't solve the problem.

I was told that it could be that the exhaust valve needs re seating. Does that sound plausible?

Any other suggestions?

Thanks and Regards to you all.

K

Been fiddling with it today.....

White smoke when idling that gets progressively worse as it accelerates. Stinks of unburned diesel. Checked all the hoses as best I could and there doesn't seem to be any leaks or weak joins.

Put a can of Wynn's EGR 3 down it to see if the EGR valve was playing up.

When I unplugged the injectors one by one it obviously dropped to 3 cylinders but there was no difference between pot 4 and any of the others. So is there a compression problem with pot 4?

I haven't noticed it using any more fuel.

Cheers

K