Header fuel tank 415d

Jim,

On my plane, the wing fuel shutoff is "on" when the lever is vertical. I would double check that. The lever, when in the "on" position, should point in-line with the fuel tubes connected to it.

The nice, simple solution I'm hoping for is that turning the wing tank lever "on" starts feeding your fuel pump.

Thanks brooks new information the wing tank valve was off the header tank was down 3 gal coming back from annual. This was the first I have seen the plane. Returned wing tank value for an aft which looks correct on the line. Filled the header tank, no more fuel out of the wing vents. But still did not get any fuel pumped from the wings. My next step is to check the restrictor orifice to see if it is plugged or maybe fuel pump is bad, or lost prime. Any other suggestions? Thank you, Jim

Jim,

(1) The header tank being "1/3 low" after sitting might not be a problem at all... especially if the "1/3" was the float gauge being down by 1/3. This is usually a LOT different than the tank itself  being down by 1/3.

To test the float gauge on my plane, I completely emptied the header tank and then started refilling it one gallon at a time. My float gauge doesn't even start rising until 3 gallons are in the tank. With 6 gallons, the gauge comes up to where I call "full" but that's not to the top of the float tube. You can pour in a little more fuel and make the float go higher for a couple minutes, but that excess fuel drains into the left wing pretty quickly. Once the fuel stopped draining into the left wing, I marked a line on the sight glass to show my "full" float level. 

If you look inside the nose tank with a borescope, you'll see that there are three ways for fuel to get in & out. In the pilot-side wall of the tank, there's an inlet from the fuel pump and an overflow to the wing tanks. At the rear of the bottom of the tank, there's a drain to the gascolator. The inlet from the fuel pump is a little lower then the overflow... and the overflow determines how full the tank gets. But if you park for a while, the top level of the fuel is above the fuel pump inlet and can slowly drain backwards through the fuel pump and back into the wings. This takes a few hours on my plane and drops the nose tank level by about 5/8 of an inch.

This might be why your nose tank looks lower after sitting. The float gauge can exaggerate the amount because it's really only showing the "top" 3-4 gallons and there's 2-3 gallons of hidden capacity below the float.

(2) The wing tank overflowing might be a problem, or it might be completely normal. I know of 4 reasons you can see a fuel overflow:

(2A) Your fuel pump doesn't have the required restrictor fitting. Without the restrictor, the fuel pump will pump will overwhelm the nose tank overflow that sends excess fuel back to the wing tanks. When this happens, you'll have fuel bubbling up into the float gauge and splattering your windshield as the nose tank vents itself of excess fuel.

(2B) Your fuel tanks were just really full. Lets suppose I land and then fill both wing tanks all the way up, and then park the plane. Over then next couple hours, the aforementioned top 5/8" of nose tank fuel will seep backwards through the fuel pump into the wing tanks. The wing tanks now overflow. Not a problem... just don't fill that high next time.

(2C) Your fuel balance line got clogged or kinked. This line links the left and right wing tanks and keeps them level. To test it, empty the wing tanks and then fill one of them completely. In 15 minutes, both wing tanks should be half full. If this line is obstructed, normal fuel overflow from the nose tank, which enters the left wing tank, would not able to flow across to the right tank. This would gradually overfill the left wing tank.

(2D) Your fuel tanks were just really full, part 2. This one is a little more subtle. Imagine the plane is parked with all three fuel tanks are full... just barely not overflowing. Now you start the engine. The fuel pump starts pumping fuel to the nose tank, where a little goes to the engine but most overflows to the left wing. That left wing tank was already full, and as overflow fuel arrives, the level in the left wing tank wants to rise. Ideally, this fuel flows across through the balance line to the right tank, but when 100% full there's no room for the left tank to build any head pressure to encourage fuel movement. Plus, a solo pilot sitting on the left makes the left wing tank sit fractionally lower than the right wing tank. The left tank can start overflowing a little at this point. Once you burn enough fuel that the fuel level in left wing tank has room to be about 1/2" higher than the fuel level in the right wing tank, gravity supplies enough head pressure to stop the left tank from overflowing. This happens right away of you have an electric fuel pump because they run 100% all the time. With an engine-driven fuel pump, it might not happen until you increase RPM.





 

  
 

New to me Encoupe...it has been in a hanger for a month & the Header tank was full when we parked it. Today the header tank is 1/3 full, but the fuel had been shut off to carb a month ago. We turned on fuel value and started plane. Header didn't fill as it was flown and began to push fuel out of the right-wing cap. Where do we start?