Joined: Wed Nov 17, 2004 11:47
Location: Kewanee, IL. (EZI)
A lot of talk has been generated about our poor, inaccurate model "A" fuel gauges. I have found them to be very reliable, but it takes some work to get them there. The gauge on my Champ plagued me for a year, before I finally got the problems fixed. It has been very reliable and fairly accurate for the past four years. (900 hours of flying)
Probably the biggest complaint, or concern, is leakage of the gauge, whether a nose tank, or especially the auxiliary tanks in the Chiefs.
Several outfits stock the replacement parts. I have enclosed a photo of the parts supplied by Snyder’s Antique Auto Parts. (Photo 1)This particular kit comes with a new varnished cork float, complete gasket set, the brass bushing that goes in the float and the brass washer that keeps the float from coming off the rod. I will provide links and part numbers at the end of this article.
First, I should explain the removal of the gauge. To remove the gauge from our nose tanks, takes a large open end or crescent wrench. Don’t hold me to this, but I believe the hex size is 1 ¼ inch. I use the crescent wrench, so I am not positive. There is a special wrench for the knurled ring on the Chief Aux. tank, or a strap wrench can be used. I have seen many destroyed by using pliers. If you warp the ring on these, they never will seal right! Paul Gould, from Sardinia, Ohio, has someone that makes these rings for him. They are pricey, though.
Using the correct tool, remove the large hex nut, which is the outer ring of the gauge. Then, carefully pull the whole assembly from the tank. It all comes out the hole on top of the panel. You have to get the right twist/turn to get the float out. Be gentle!
Next, there is a special tool to remove the glass that covers the indicator. I
made mine from a piece of 3/4 inch square bar stock. Carefully unscrew the plug, then remove the metal piece with the indicator alignment marks (- -), the gaskets and the glass. The original glass viewer has a raised oval that protrudes into the oval slot in the metal piece. If the glass is still clear, or can be cleaned up, keep it and reuse it. Some turn yellow and cloudy and won’t clean up. The kit comes with new, clear glass, but it is flat. If you noticed when you removed the metal piece that covers the glass, there is a tab on one side. There is a hole on the top and bottom of the housing that the tab gets inserted into. Locate them so you know where they are at. When it comes time to reassemble the gauge, the metal piece will have to be inserted on an angle, tab end first. When you get the tab into the hole, the rest of it will almost fall into place.
Now look at the float rod, where it connects to the rocker. I have a pen pointing to it in the photo. (Photo 2)
Grab the rod and the gauge and twist, to see if there is any movement at all. If there is, you need to secure it. This is just pot metal, so use what works, but make sure it is fuel proof. I used J.B. Weld. You probably noticed the float is perpendicular to the gauge. If the rod is not tight in the gauge, when you fill up, the float rises, but the rod turns in the gauge instead of moving the gauge to read full. What is worse, it won’t read accurate when you are empty.
Check your float. You may not need to replace it if it looks good. If you don’t replace it, check the shellac coating. Now is the time to redo it. Shellac has worked well for years, but if you get any auto gas that has alcohol in it, it will eat the shellac right off. If your cork gets gas soaked it won’t be accurate. You have a couple of options here. Change to a brass float or an automotive type of plastic float, re shellac (at least 3 coats) or use epoxy varnish on the cork. This system seems indestructible. Make sure the float is completely dried out before you seal it. A plastic float is available from Snyders.
Now we reassemble the gauge. Locate the two small cork gaskets in the kit. Place a gasket inside the housing, then the glass, metal plate (don’t forget, tab first), the other cork gasket and finally the retainer nut. Snug the nut down, but don’t over tighten. With the metal pressing directly on the glass, over tightening can crack or break the glass. Don’t ask how I know this!
Before we go any further, it’s time to calibrate the gauge. Put the tail up and level the wings. Drain the fuel tank that you are working on. Once drained, carefully install the fuel gauge in the tank, without the gaskets. Rotate the gauge with your hand, so the indicator reads straight up and down, not crooked. Hold the gauge in place with your hand and observe the reading. The “0” or empty should be centered in the viewer. I did this with one gallon (measured) in the tank. I didn’t want it to be empty when I saw the zero appear. Remove and bend the gauge until you get the zero centered. That’s the important reading. When you have accomplished this, remove the gauge. Slip the large cork gasket over the float. I put a little hyplomar gasket material on it, just to hold it to the back side of the gauge, so it won’t fall off.
The gasket is smaller than the rocker that has the readings on it, so you have to slip one side over the rocker, move the rocker to the other side and seat the rest of the gasket. There is a grove on the back side of the gauge, where the gasket is supposed to set, so make sure it is centered. Re-insert the gauge assembly into the tank. Locate the copper gasket and put it on the gauge, then the hex nut. Align the gauge again, so the numbers are vertical and tighten the nut.
With a measured can, put 1 gallon of fuel at a time in the tank, observing and logging the readings after each gallon, until the tank is full. On my champ, (13gallons) at ¾ it takes @ 3 gallons, ½ @ 6 gallons, ¼ @ 9 gallons and @ 11 ½ gallons on 0. Remember, I zeroed with some fuel in the tank.
Lower the tail and check for leaks. In three point attitude and full tank, the fuel is a little higher than the gauge and leaks will show up.
Well hopefully, this will cure your gauge woes. Mine has worked flawlessly for over 900 hours now.
Gauge Assembly (Complete) #A9312
Rebuild Kit #A-9320-s
Cork Float # A-9312-c
Modern Float #A-9313-c
Tool Set #A-9300
Gasket Set #A-9321/23 (cork)
Glass Lens #A-9323
Face Plate #A-9325
Inner Nut #A-9326
Outer Nut # A-9330
This article written by Jody Wittmeyer for the National Aeronca Association. Not to be copied, forwarded or reprinted without permission from the author!
Blue Skies and Stay Safe, and preserve 'em