fuel tank issues on 48 C-170

[N2645V]

My outboard right wing tank does not fill as much as it should. I get 1 1/2 hours flying on the left tank which would imply a 8/GPH fuel burn while cruising. The right fuel tanks give me only just over 2 hours flying time. It should get me 3 hours. I will open the right side up to look at the fuel and vent hoses between the 2 tanks. I have started looking into adding a fuel cap to the right outboard tank. My thought is an unvented cap would not change the fuel tank venting at all and make faster fueling possible. When possible I want to add a outboard tank on the left side with a fuel filler cap on that tank also. I hope someone may have done this and could offer a look at the 337 or other paperwork that made the FAA easy to deal with... Thanks

[DWood]

The outboard tanks do fill slower. If you take out the outer tank to replace the hoses, you might consider adding a fuel drain. It will take a field approval but will allow you to get water out of that tank. I have never heard of anyone adding caps to the outboard tanks, but that certainly doesn't mean that it hasn't happened.
Dan

[n3833v]

If the bottom feed and top vent lines are OK, it doesn't take too long to fill when fueling. The lines are only from inboard to outboard tanks. You don't need any fills on the outboard tanks, just an extra inlet for water.

John

[Bruce Fenstermacher]

So John your saying you need an extra inlet for water on the outer tank.

Oh I see the extra fuel port would be an inlet for water.