Fuel primer leak..

[CF-HEW]

I noticed some fuel dripping under the instrument panel while I was priming the engine. Upon further examination, I determined it was coming from where the fuel exits the primer where the nipple clamps the copper hose. I have tightened it as much as I dare to but there is still a small amount of seepage between the hose and the nipple anytime the fuel selector is in any position other than off or if I action the primer. Any Ideas?

[Bruce Fenstermacher]

I'd guess maybe the flare on the copper tube has cracked. I'd take it all the way off and look at it. Depending on how the line is run yo might be able to cut off the old flare and reflare the tube. Of course if original it's probably getting pretty hard and subject to cracking and now might be good time to replace it.

[GAHorn]

I'd guess maybe the flare on the copper tube has cracked. I'd take it all the way off and look at it. Depending on how the line is run yo might be able to cut off the old flare and reflare the tube. Of course if original it's probably getting pretty hard and subject to cracking and now might be good time to replace it.

...and you're likely to find it's a 1/8" copper line which requires a double-flare. (Expensive tool...you'll want to find a mechanic/shop with the tool to borrow.)

[lowNslow]

...and you're likely to find it's a 1/8" copper line which requires a double-flare. (Expensive tool...you'll want to find a mechanic/shop with the tool to borrow.)

The stock lines are not double flared, In fact I don't think there is a tool that will double flare 1/8" line.

[GAHorn]

AC 65-9A (A&P Mechanics General Handbook) says that 5052-O and 6061-T alloy tubing from 1/8 to 3/8 should be double flared. No mention of other alloys, but 1/8 copper should be double flared according to our resident aeronautical engineering-type, Cleo Bicford. I haven't found anything in writing about it.

[CF-HEW]

Awesome guys. Thanks for the quick reply as always. I will call my mechanic and see if he has the flare tool.

[GAHorn]

Here's another option..you can silver-solder AN800 primer bulbs/fittings:


http://www.aircraftspruce.com/catalog/h ... ttings.php

[lowNslow]

The primer line I removed from my manifold had the above AN800 (soldered) with the AN805 nut and the AN4022-1 spray nozzle. I romoved the AN800 and re-soldered it the new copper line. All the other fittings were single flared with collars.

[CF-HEW]

What I thought was going to be a fairly straight forward job turned into a bit of a nightmare. The copper line kept cracking as we were flaring it. In the end we drilled a countersink into the line and heated it up before flaring it very very slowly. That did the job.

[GAHorn]

Copper becomes brittle/hard due to age/vibration and work-hardening (bending, flaring, etc.) Annealing it (heating) "relaxes/softens" it again. It's actually a poor material for airplanes but few alternatives existed in times past. A few 1/8" lines were made with aluminum, but corrosion is a problem and small aluminum lines do not survive long if abused. Modern rubber mfr'd hoses and stainless lines are better. (Stainless fuel injection lines can sometimes be substituted if you have access to them but should be bent with proper tooling. They are already equipped with the "bulbs" previously illustrated, and are probably as close to "permanent" as possible.

[cessna170bdriver]

If you're going to anneal copper, just heating it then walking away won't do as well as heating (cherry red) then quickly quenching in water. I do it to my spark plug gaskets every time the plugs come come out.