[Ernie Martin]

I wrote the article Frank indicated, but I had not responded to your inquiry because I didn't have an answer. Three things come to mind -- but it's speculation and may be wrong -- and may be worth checking:

a) the fuel pump on the front engine is weak,

b) the fuel path from the left aux (I'm assuming you meant the left aux at 10.0) to the front engine is partially blocked, or

c) less likely, the return path for fuel and vapors from the front engine is partially blocked.

If you read my article, the engine normally draws roughly twice as much fuel as it needs, returning the unusued fuel always to the main. This happened on the rear engine, where the engine drew 17.7 gallons from the right aux, used roughly 9 gallons and returned the excess to the right main. However, in the front, operated for the same amount of time, only 10 gallons were drawn from the left aux. It should be more. Closer to 18. The only explanations that I can see for drawing less fuel than it should are the ones listed above.

If your full power take-off has been normal, with the gph needles on both engines at or near 18 gph and the front engine developing full power, it's probably not a weak fuel pump (point a)).

You could do a test to see if it's point b) by doing a high-speed run on a LONG runway with both engines on their auxiliary tanks (do NOT take off; reduce throttles to idle before you get to the runway mid-ponint). When you give it full power look at the gph guage, RPM and manifold pressure. If all normal, then it's probably not point b) -- and I'm stumped.

Good luck.

Ernie