Fuel lines

[jonbakerok]

I'd be interested in hearing what people are using for flexible flexible lines to solve the alcohol problem.

[Dave S]

Jon,

Since N128DD is using auto fuel - it has SAE (automotive) fuel lines. Originally the standard low pressure lines were installed, however, it became apparent that a minute amount of vapors would penetrate the hose and a slight fuel odor could be detected in the cockpit although there were no leaks. The low pressure SAE lines were replaced with the high pressure Automotive fuel injection lines (that would be the $5.00 per foot stuff) and the stink went away. One other person at the airfield N128DD is based had the same experience with SAE low pressure VS SAE fuel injection hose. The SAE fuel injection lines have some sort of liner - don't know if it is teflon, or poly or something else - but it has a medium blue color and is a whole lot more rigid than fuel resistant rubber liner of the low pressure SAE type.

I am sure the 582 fuel system is different from the 912 system so the following comments may or may not be useful.

As an overall system test - before initial startup I did a fuel flow test - Filled the fuel tanks - disconnected the fuel hose down stream of the fuel pump, sat there with a stopwatch and gallon can to get a flow rate. Also did flow rates with the electric pump running and upstream from the mechanical fuel pump. These flow rates will be repeated as part of the annual condition inspection, and, whenever anything in the fuel system is changed (like when the hoses were swapped out). I wanted flow rates to have a base line to compare with in the future - as an indicator of overall performance (flow resistance). Also did a pressure test of the electric pump with and without the engine running - & mechanical pump alone with the engine running - again - the idea is to see if anything changes in the future.

Another materials test a person can do is take a chunk of each type of fuel hose used and and dunk them in sealed jars of the same type of fuel a person intends to use - then leave them in the corner of the hangar for a loooooong time and see what happens to them.

For what it is worth - swelled shut fuel hoses on cars were not unknown to happen in times long before we had corn gas. Back then we could not blame corn-gas because there wasn't any. I don't know that anyone ever figured out what caused this - but mechanics generally blamed poor fuel line materials or fuel contamination (car gas has been known to contain other solvents aside from pure old gasoline) - and it usually happened on hoses which were in service for a long time.

At any rate - with the restricted fuel line - glad nobody scratched up any paint on this and glad the problem was discovered.

When it comes to fuel systems - and all the statistics on fuel system related engine failures - I haven't decided if I am paranoid - or not paranoid enough - I have decided it is good to check the heck out of the fuel system - frequently.

It would be interesting to hear of any procedures anyone has developed to evaluate and maintain their fuel system for safe operation. Also interested in other experiences anyone has had with other fuel system components - like pumps, filters, etc. how long they last, etc. Really interested in how long auto fuel filters last, or are replaced, on Kitfoxes.

Sincerely,

Dave S
Kitfox 7
912 ULS

[darinh]

You can use Aeroquip AQP socketless hose and various other Aeroquip hoses (the AQP is good for ethanol also - so I was told by Aeroquip). Another option is Goodyear Hysunite fuel hose you can buy at most local autoparts stores. Dave brings up a good point though with the low vs. high pressure SAE stuff. I have also seen a fuel hose called Fire-Acol in the marine shops that specifically says it is good for ethanol fuel. I ran as much aluminum tubing as I could but am currently in the process of changing out all the Mil 6000 stuff that comes (or came) with my kit to either Aeroquip or I may take a look at this new Fire-Acol stuff.

[JimS]

Wally
I had the exact same experience as you ,probably within 5 miles of the Tomahawk airport (a grass strip owned by Dick Lee). Anyway, in my instance,on takeoff, at about 200', I lost probably 75% power. I had a Facet fuel pump that I turned on and the problem went away. Long trouble shooting story made short, I found that the pulse line coming off the nipple on the crankcase had the hoseclamp just overhanging the barb, and don't we all just give those hose clamps a little tweak at every condition inspection and maybe a few times in between? Yep, I had reduced the I.D. to about 30% and just like you had enough fuel to fly straight and level at cruise power, but pull the nose up and go to full power and you can guess the rest. I had put the facet fuel pump in and used it instead of the primer for starting but it saved my bacon that day.
By the way Wally, I don't think I've ever met you, but you should check out our flying club, UL Chapter 75. We've got members from all over the state and about 8 or 9 Kitfox/Avids in our group.

JimS

[wadeg]

Have been using the Napa auto fuel line and have not seen any problems whatsoever other than a small eau de gas occasionally.
I dunked some in some ethanol to see if it would be harmed and it seemed fine after I forgot about it for a few weeks sitting in the hangar. No swelling or changes noted whatsoever.