AviationBanter - View Single Post - Citabria Fuel-Flow Problem

**Bertie the Bunyip[_25_]** · May 9th 08, 01:39 AM posted to rec.aviation.owning,rec.aviation.piloting

quietguy wrote in news:b8a07cf2-f01e-4dba-9793-
:

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?

OK, talked to my guy. He had several suggestions. One is to drain it all
dry and then blow some air (carefully!) into the right tank and see if
you can hear it coming across into the left tank by listening at the
filler cap.
Possible problems he came up with were a crushed or swollen fuel line
downstream of where you tested previously, or, he thought more likely,
incorrect placement of the little plastic fuel vent deflector and/or the
location of the fuel vent itself. There are specs for the location of
these if you look in the manuals. But for the fact that the fuel doesn't
migrate when parked, I would have said this is definitely your problem
For instance, Cessnas with bent or incorrectly positioned vents are
chronically out of balance.

Bertie