Unbalanced fuel usage

[CFIDave]

Are you sure nobody's stealing fuel out of your tanks on the ground?

Seriously, I've never heard of a situation like yours.

[Karl]

I would be looking at the transfer valve for rigging, installation or internal leakage.

Not only does the transfer valve allow the left engine to run on the right tank (and vice versa) but it also redirects the return fuel.
The valve dependent upon position can send the return fuel to either the left or right tank.
An internal leak, hoses connected to the wrong port or simply bad rigging so that the valve is not fully closed could cause the issue.

[MMcfly]

Thanks for the comments. We have now heard that another DA42 has had a similar problem so we are investigating how that one was fixed. I will report back any findings.

[ememic99]

Check fuel temperatures in both tanks to see if both cross-feed valves are fully closed.

[MMcfly]

Thanks for the replies. After a flight today the problem has gone away. We are convinced that somehow the fuel selector valves were not fully closing after the cross-feed check and lots of ground checks and movement of the levers has somehow rectified the issue.

[Karl]

Excellent news.

Sounds like we were on the right track with fault diagnosis.

[ememic99]

Excellent news.

Sounds like we were on the right track with fault diagnosis.

Well... I nailed it in the first guess