Citabria Fuel-Flow Problem

On Wed, 7 May 2008 11:17:24 -0700 (PDT), quietguy
wrote:

The A/C in question is a 1974 Bellanca 7ECA, re-engined with an O-320
so it's effectively a 7GCAA. It belongs to the Offutt AFB Aero Club
and has seen very little use, often sitting for weeks at a time until
a week ago when I began taking dual in it 2-3 times a week to get my
tailwheel endorsement. The fuel system is not for inverted flight, so
no header tank -- two 18-gallon wing tanks with check valves to a
single vent on the left, crossflow pipes to the aft fuel manifold
under the baggage compartment and crossflow pipes to the forward fuel
manifold on the firewall. Caps are non-vented and the gaskets are
like new.

This A/C is drawing 3-4 times as much fuel from the left tank as from
the right and it's not crossflowing on the ground, even overnight.
We've made right patterns as well as lefts -- makes no difference. We
haven't done any extended S&L flight, just 11 NM to Plattsmouth, NE
for pattern work. The club's A&P has blown out the feed and vent
lines and got a good blast into the right tank from both. We're
getting a free flow of clean gas out of all four drains.

So what's our next move? Anybody had this problem?

does the fuel situation change if you swap the caps to the other tank?