LM701 STOL N1345L
Fuel Line Routing
I recently reworked my fuel delivery system. There are several reasons why I changed the system. First I had several leaks which were due to my accidentally drilling several holes in my tanks. Second, I found the poly type fuel lines furnished with the wing kit to be total crap. I found three splits in the lines which were leaking. Also no longer than they had been installed, they were starting to harden. My advise is to stay as far away from poly lines as possible. Here is a picture of one of the splits in the old line. This line was touching nothing.
And third, I had intended to use a fuel injected engine and had plumbed for fuel return lines with a six way switch. When I purchased the Harley Davidson engine from Hog-Air it was with the promise of fuel injection. Unfortunately, Hog-Air could not make it work. I was therefore forced to use a carbureted engine or revert to another type. Hog-Air did offer me a full refund.
On one of my other pages entitled Fuel Tanks, you can see the extensive use of the poly lines. I remove them all and replaced them with automotive fuel injection line. Slightly heavier, but I trust them. I have rebuilt cars that were 30+ years old and the original fuel lines still did not leak.
After fixing my tanks, which I did by popping rivets in the holes and melting plastic over the heads, I redid the venting system. The original venting system was to vent the inside tank to the outside tank and then to the wing tip. The problem was that if the outside tank was full of gas the inside tank would not vent, plus the venting tube was too small. I vented all four tanks separately for each other. I used finger strainers over the ends of the venting tubes to keep the bugs out. Here is a picture.
I started routing the fuel lines with new line from the out side to the inside tanks. I installed 3/8" balance lines between them with a manual valve between the two. This allows me to cut off the outside tanks unless I am planning a trip.
Then I installed new 5/16" line from the inside tanks to the cabin. Inside the cabin I ran the lines down the windshield posts with a manual valve on each followed by a see thru filter. Here is a picture of the inside of the cabin.
Then I went thru the firewall and joined the two lines with a Tee fitting.
From the Tee fitting I used a single line into another Tee fitting with one output into the primary pump and the other into the secondary pump. The primary pump is running anytime the key is on and the secondary pump is on a switch inside the cabin.
Normally a carbureted engine in a high wing aircraft depends on gravity feed alone, possibly with a pump back up. The Harley carburetor has a very small bowl and I felt that in a climb where the carburetor could be higher than the wing tanks it could cause fuel starvation. I decided to run a pump all the time thus eliminating the need to remember to switch on the pump. I will use the secondary pump for take offs and landings.
After the lines come out of the pumps, I Tee them back together with a single line going to the gasolator. Then thru the pressure regulator, which is set at 1/2 lb to the Carburetor.
I also installed some new low profile gas caps. Here is a couple of pictures. Notice the new service doors on each side of the tank.
You can find the caps at www.seachoice.com.