AAZ Pump Leak Question

After investigating a strong smell of diesel, I’ve found a leak in the fuel pump.

It’s dripping from the lower rear of the pump, under where the injection pipes connect. 

There is a small black plastic cover (approx the size of a 10 pence piece), which has an electrical lead coming from it (not used).

Any idea what this cover is? What’s behind the cover? Can it be re-sealed etc

Or is there anything else in that area that typically can cause leaks?

It’s a pretty hefty leak - dripping at a rate of 1 drop every 3 seconds at idle.

Without a pic it is difficult to accurately identify what part you are talking about.

Late AAZ pumps have a few extra bits as they moved into the electronic era just before TDIs.

IIRC the late AAZ pumps have a lift sensor of some sort on the pump head (rather than on the injector as per TDI) that indicates commencement of injection.

There is also another part in the area you describe that I understand might tweak timing advance.

Both of these parts may be tied in to some sort of circuitry to enhance emission control during the engine warm up period.

Fairly certain both will have some kind of gasket / sealing washer / O ring where they mate to the pump so it should be easy enough to replace them once we actually identify where your leak is coming from.

Leaking at one drop per second. At the very least we’re  going to need to remove the pump, so may fit a 1y pump that I have spare in the meantime.

It’s actually a 1Y engine with a turbo and with an AAZ pump. It did have a 1Y pump fitted originally, and ran really well, but the head was damaged during glow plug removal, which necessitated a head rebuild and we ended up fitting the AAZ pump during post rebuild trouble shooting.