Changing Header Tank, Fuel and Vent lines-Hints, Tricks, Experience Welcome!

[PNWJARED]

I will be updating my header tank, I will be changing out the plastic molded tank for the aluminum. in addition I will be changing out the fuel lines, the vent lines mostly in an effort to alleviate the fuel smell I get in the cabin. Any experience our thoughts, advice ect... is welcome.

I have a new aluminum tank purchased from Kitfox.
-Remove old replace new in kind.

I currently have one fuel shutoff and one fuel filter each side from wing to Header tank.
-Upgrade fuel line to same size but use fuel injection line(Non Vapor Permeable)
-Eliminate the fuel shut offs (Only fuel shut off will be at console)

Vent line is Tygon tubing ran to one wing

-I have tried to follow the multiple AD's on the matter. Most of which are from
earlier models 4 & 5 i think.
-My vent line seems to have fuel in it?? its that ok or normal?? A little input in
proper venting procedures would be nice. Though really it seems connect A-B
-I do like to utilize a slip. I am a little unsure if fuel in the header vent is normal

Any other thoughts hints or tricks would be nice.

[PNWJARED]

I have a Kitfox 7 early version

[jrevens]

Yes, fuel in the vent line is normal. The fuel in that line will be at the same level as the fuel in the main feed lines from the tanks.

[Dave S]

Jared,

Based on your post, I'd say you have it figured out. I think you will like the new tank and the non-permeable lines. We have no fuel odor in the cabin with the new setup (Aluminum tank and non permeable lines) - kinda stunk before I changed it.

You can slip to your heart's content. I have found that it is possible, with full fuel tanks and a maximum slip, to squirt a little fuel out the down wing fuel filler cap pitot and have it hit the tail in front ot the HS - but not a big problem.

Curious - do you have the manual trim? We do in our early S7.

[PapuaPilot]

You mention removing two fuel filters from the tank supply lines. I just want to make sure you have a fuel filter somewhere in the system before the fuel enters the carb/engine.

[PNWJARED]

i was going to remove the two shut off valves. I think there is differing opinion on wether or not to leave the filters at that location. I don't see the harm plus you can visually see if your getting a lot of sediment out of the tank. I don't think they will add any odor. but changing them means fuel in the cockpit again. Maybe best to put them somewhere else. Any suggestions.

Yes I have the S7 with manual trim tab. I don't mind the arrangement though I believe it diminishes the elevator authority. I feel like I run out of elevator. I may want at some point to convert to the SS7 trim at some point.

[PapuaPilot]

You need to have at least one fuel filter somewhere in the system after the main fuel selector but before fuel goes into the engine. That is what I have in my plane and it is going to get inspected for the first time later this week (25 hrs since new).

If you wan't to keep the inline filters in the cabin I would suggest leaving the two shutoff valves installed so that you can remove the filters with out draining both tanks.

I personally didn't feel it was necessary to put extra filters in my plane. Some of the dirt and sediment will get caught in the header tank and the rest will get trapped in the fuel filter. Most of the stuff in the header tank will get removed when you sump the tank, but it would be prudent to remove and clean out the header tank at some point.

[Av8r3400]

Gravity is the only means of flow from the wings to the header tank. IMO, putting a filter there is a mistake. Even one you can see through. When you can see its clogged doesn't keep the fuel flowing. You'd need to land and replace it, maybe not an easy thing to do.

The place for a filter is between the header and mechanical fuel pump. Be it a screen on a gascollator or a large, non-paper element inline filter., replaced annually. There is a non-serviceable screen in the mechanical pump on a 912. You should filter before this screen.

I do believe in shutoff valves for each wing. If you park on an incline this will keep from transferring fuel down hill, possibly overflowing. (Been there... :rolleyes:) These also help in maintenance if you need to work on the fuel system, you won't need to drain wingtanks.

[PNWJARED]

great advice guys thank you.

So in regards to the vent from the header, its ok to have fuel in the vent line... Check.

So it is also natural for one wing to have 2 gallons and the other 8 gallons. Do I worry when the one wings is empty and the other has 5 or six?? it is all running to the header, so..... No Worries??

[Dave S]

Not OK...mandatory

Another way to look at it is if there is no fuel in the vent tube - it would be good to have a landing strip immediately available;)

[PNWJARED]

Am I missing the point of this line. the fact it is called a vent line typically means this line has air?? Is it not a vent line? or should it be called something else. to me if this line has fuel it is not venting the header tank. Though the header tank in effect becomes part of the wing tank which is vented thus not really requiring a vent at all??? So what is the point of having it??

[Av8r3400]

It vents the air out when initially filling. After the tank is filled with fuel the line then also fills with fuel.

[PapuaPilot]

That's a great question. It is a vent line. It taps into the top of the header tank and goes into the top of the fuel tank. If there is any vapor that goes back to the header tank from the fuel pump or engine it should get back to the tank via this line. The fuel supply lines come out of the lowest point of the tanks and go into the header tank. The vent line should always have the approximately the same fuel level as the fuel tanks.

If you have fuel in either tank it will go by gravity to supply the header tank.

The purpose of a header tank is twofold:
1. To provide a place for vapor to go to return to the fuel tank. The return from the engine or fuel pump needs to tap in above the fuel supply to the engine so it doesn't just draw air back to the pump/engine. The vapor return from the header tank to the fuel tank needs to be at the top so the air can rise back to the fuel tank.
2. It provides a place for reserve fuel in case of interruption of fuel flow from the wing tank(s). Using the Kitfox as an example: if your left wing is empty and you unport the supply line from the right tank by uncoordination, doing a slip or negative Gs there is still going to be about one gallon of fuel in the header tank. Even if a bubble of air gets down to the header tank it is going to stay in the top and return in the vent line.

[PNWJARED]

Thanks Guys, you were a great help!!