Fuel system

[bwest]

We have recently purchased a model IV 1050. It seems that fuel does not flow from one of the tanks to the header tank. We have checked everything we can think of and can not find problem. Does any one have sugestions?

bwest

[akflyer]

Do you have the finger strainers in the tank? Possible that it is plugged off. Take the line off the header tank and see if fuel flows out the open line from the wing tank. A buddy had that issue after a few flights and it turned out to be the fuel line getting kinked when he swung the wing into place, even though it looked like it was OK.

[HighWing]

First a question. Is this an inflight phenomenon? If so, it might simply be the fact that various factors often combine to cause one tank to drain faster than another. In my opinion, it is most often due to the tendency of the round upper glare sheild failing to give a horizon reference and most Kitfox pilots will fly one wing low - the high wing draining first. Among other theories posited are the vent line on one tank only and its negating the effect of the pitot tube on that tank resulting in the un vented tank having a higher input pressure. A flight of 6 was once in the mouintains of Idaho and one of the guys refused to leave a remote strip until we checked his fuel flow. We undid everything and finally convinced him to leave with us and there was never an issue with fuel starvaion then or for many hundreds of hours after - though none of us ever had symmetrical flow from the wing tanks.

If it is a ground issue as well, check for a continuous down hill run on the line to the header tank. It has been often reported that a slight uphill segment can trap air and that can cause a blockage in the gravity fed flow.

[mr bill]

A recent issue of the Cessna Pilots Association had an article based on information from Cessna that said uneven fuel feed from the wing tanks has to do with the venting system. I have been flying Cessnas since 1968 and have often wondered why, no matter how I flew the plane, one tank would drain faster than the other. The venting has one tank partially supplying the the other. Interesting article.

[Av8r_Sed]

I just performed a gravity feed fuel test on my Model III. With the plane in level flight attitude with wings level and 1/2 fuel in each each 13 gal tank I found that the right tank drained completely while the left tank didn't empty much at all. The fuel cap vents breathe freely and the fuel lines from the wing tanks to the behind seat header run downhill and aren't kinked. After seeing this I figured the left finger stainer must have been plugged. I pulled it and it was clean.

I'm not sure what to do next. I'm guessing that in flight with ram pressure on the fuel cap vents and the engine driven fuel pump running I wouldn't ever see this happen. Still, I'd prefer if both tanks fed freely and evenly with just gravity. Any Ideas?

-- Paul S

[HighWing]

Paul,
If all seems clear, and assuming you are building to specs with the header tank behind the passenger seat, I would think that with the longer feed line from the left tank there would be more resistance to flow on that side and the right tank would drain first. What you might try is clamping off the right fuel line and measure the GPH flow from the left tank alone. Another thought would be to put some resistance to flow - a partially clamped hose on the right side and see if both tanks flow more evenly.

Years ago I flew nonstop from Caldwell where the factory was, to the Sacramento area. I was down to about 4 gallons each side as I crossed the Sierras and during the 30 minute descent from the high point to pattern altitude at home, I watched the old style aft ported tanks unport and saw the fuel flow from wing tanks to header tank stop. The low fuel indicator worked as planned and by raising the nose a bit saw fuel flow from both tanks resume. A couple of observations here. 1. Fuel flow was restored as soon as I raised the nose and got fuel to the outlets of the wing tanks. 2. Although there was the characteristic uneven fuel flow early in the flight, by the time I was in the critical position, the fuel quantity in both tanks was fairly even. As an aside, I had the Purelator glass fuel filters in both down lines to the header tank. I could see the fuel flowing in the filters as there was always a bit of a bubble and I could see the turbulence. I don't think I would have tried what I did if I couldn't have seen the fuel.
Further, I had 5/16" id fuel lines. I know of others that use 1/4" fuel lines throughout. Those guys have never had fuel flow issues in well over 1000 hours. I recall lots of posts from others regarding uneven fuel flow from the wing tanks, but don't recall a single engine fuel issue with fuel in the tanks. OOPs there was the Alaska group with Kreem sheeting off that blocked a finger stainer.
Lowell

[Av8r_Sed]

Lowell,

Thanks for the feedback. I've got the 5/16 lines and glass filters. My tanks were manufactured in June of '91 and are aft ported so I'll have to be vigilant on long descents. During the test the difference in flow rates was visible in the filters.

I'll repeat the test and with the right line pinched down to see if it makes any difference.

-- Paul S

[Kiriako]

Yes, the Avid Flyer has this advantage...

Paul,
you might want to have a look at my previous posting for the 'fuel, wing tanks thread' where I describe problems very similar to yours.

One way or another do check all the fuel lines for debris from the tanks. If it is heavy debris and you have an up-segment of metal fuel lines before they reach the header tank like I have you might need to blow it out with an air-compressor...

[Av8r_Sed]

Thanks Kiriako. I don't have any metal lines between the wing tanks and the header, but I will blow out what I've got and retest. I've also made sure that the routing of the lines is all downhill from the wings to the header. I want to ensure I've got good flow from both tanks before it flies.

-- Paul S

[fastfred]

This is an addition to the old post about fuel flow. I am new to this plane and fold the wings every day. I noticed the right tank was not flowing fuel. The line was kinking and could not be seen when the wings were open. Easy fix but one more thing to look for.

[Guy Buchanan]

Try swapping the glass filters to see if there's any change. They can be plugged without appearing to be.

[fastfred]

I found the gas line was kinking . I think that was the problem. But thank you I will watch those