The Murphy Builders Site

Lesson learned, run all fuel lines while the fuselage cage is still open! That said, I finally got them installed. I used the stock Murphy valves at the root rib inside the fuselage, but then used aluminum AN fittings through the rest of the system. I ran them aft and into the bulhead, using a piece of PEX to eliminate chaffing, then installed a coupling and then down and across the floor, where I tee'd them together on the left side of the fuselage. My intent is to run a single line forward to the firewall from that position. I've seen many different pictures and ways of installing a gascolator. Some have put the gascolator under the floor at the low position. Others have installed some type of line drain at the low point and the gascolator on the firewall. My primary concern is easy access. I would appreciate your thoughts on where to position the gascolator, low point or on the firewall with a drain at the low point. Also, how to best attach the fuel valve to the root rib.
Thanks,
Jerry Folkerts

I am injected, so I didn't bother with a gascolator. I go from the tanks with finger strainers to the floor mounted selector valve to efii filter then efii boost pump then flowmeter then thru the firewall to the engine driven fuel pump then into the fuel servo. If u are injected consider ditching the gascolator IMHO. -neil

Sorry Neil, but the gascolator isn't there to be a filter. It's to catch any water in the fuel or larger debris instead of the noise maker going quiet! Absolutely necessary and mandatory on this side of the 49th.

In the 10+ years of having my rebel I have never had one drop of water in my drains. Just wondering if that is normal for everyone. I use mogas and it is kept outside during the summer.

Ray Mason wrote:In the 10+ years of having my rebel I have never had one drop of water in my drains. Just wondering if that is normal for everyone. I use mogas and it is kept outside during the summer.

Yeah, same here, have never seen any water in my tanks, or gascolator. And we live in a wet climate. I have had mine docked on the ocean for days at a time, where the outside of the plane was dripping from water (dew) in the morning, because of the cool outside air and warm water. Thought for sure would get some condensation in the tanks under those conditions,... but never saw a drop of water in the fuel.

Having said that, not saying should go without a gascolator or skip fuel drain checks. You never know when you might get water from a bad fuel fill.

Yes Irishfield, I know a filter is not a gascolator. I just was giving a complete description of my io-540 fuel system. FWIW, I built a vw powered sonex also. On the sonex I went without the gascolator as well. Because of the low fuel flows in the sonex and the high temp under the cowl it just ends up picking up more heat and vapor forms before the fuel reaches the aerocarb/injector. This is a gravity fed system so almost no fuel pressure. I do have a low point drain on the sonex, never anything but 100ll comes out.

Alright, let's get this thread back on track and see if someone can offer suggestions to my questions.
Thanks,
Jerry Folkerts

Jerry Folkerts wrote:Alright, let's get this thread back on track and see if someone can offer suggestions to my questions.
Thanks,
Jerry Folkerts

Yes, sir!!...., lol. My vote is gascolator at low point on the firewall side. I also have drains on my lines at the cabin low points for when it is on wheels (taildragger). When on the amphibs, the gascolator is the actual low point. Why do you want to attach the fuel valves to the root rib? Mine gets enough support just from the lines.

Jerry Folkerts wrote:Alright, let's get this thread back on track and see if someone can offer suggestions to my questions.
Thanks,
Jerry Folkerts

Um, I have a 540 like you and gave you an exact run down of my fuel system on my completed flying airplane that works great. Others described there experiences. I do not know what else you want, but I'm done trying to help.

Hi Jerry !
Just me - I would go with just a flush drain on the outer floor (belly),
ahead of the tee, so it would be easy to check on walk-around,
AND put the gascolator on the low point on the firewall.
You do already have flush drains on the wing tanks ...

Have seen L shaped brackets used to support the fuel valve -
about 1"+ wide, with a hole for the end of the valve, with a
rubber grommet to dampen vibration ... could go with 2,
one front, and one back, for better support .. or some
variation ... The fuel line provides support, but loads
can get high if the valve seals get stiff (bad fuel ??).

It is the lowest point in the system except on the ground where there is about six inches of line in front of the carry-through which may hold a teaspoon full. If there was any water there it would be in the gascolator on the check and so would never get to the engine.

I used to have a 172 parked outside very near where Walter is now and I have found water in the system. Maybe two tablespoons full. I have also had an engine quit due to water in the carburetor bowl. It wasn't the water but some corrosion that it caused, which then caused a failure of the float valve to seat and the engine flooded. We were airborne but managed to get back on the runway, without erupting into flame. I have found water on other occasions as well and I would rather find it in the gascolator.

Well, Bob, as you probably know, just a few days ago a Cessna crashed at Pitt Meadows, right after take-off. They found 2 litres of water in his tanks. Apparently it sat for quite a while. Supposedly, they did a fuel change, but obviously didn't do a good enough job purging the water from the tanks. Not sure if Cessnas are more susceptible or not, but I know it matters what type of gas cap you have, too. The flush type ones can seep water if not sealed properly.

PS: Sorry, Jerry, hopefully not too far off track...

Hi Jerry,

I mounted the Murphy supplied fuel valves using an angle riveted to the top door channel and two Adel clamps to firmly attach the valve to the angle. I will also add a spacer between the back of the angle and the wing rib to eliminate any movement of the angle/valve during actuation.
I am using a gascolator mounted just in front of where the fuel lines tee. I used a 1/4" angle to mount the gascolator to the bulkhead, and a channel on the other side of the bulkhead to make the setup very stiff. I didn't want anything moving during fuel testing. There is an access cover underneath for removal of the gascolator bowl for inspection/cleaning.
I have an electric fuel pump mounted forward of the gascolator and then the aluminum fuel line running forward to the firewall.

Sorry Jerry.. coming in from the shop on 2 hour cycles, checking email waiting for Doctor replies, and thought I had better point out a safety concern / issue. I won't bother next time..

I always checked for water ever pre-flight and was wondering if I was wasting my time as I had never seen a drop. Then a couple years ago in early spring my plane had been sitting outside for a few weeks with the tanks only 1/4 full. I checked for water and found lots, probably a 1/2 gallon between both wings. The temperature swings and high humidity must have caused condensation in the the mostly empty tanks. Now I keep my tanks full and have not seen a drop of water since, and I don't wonder if I should bother checking for water anymore.

Allen H