Fuel leak at firewall

[GrassStripFlyBoy]

Opened the cabin door to fly this morning, strong smell of fuel.  After checking everywhere identified some wetness on the inside of firewall where the wing lines T together, I believe it's on the cabin side.

MM does not show much for detail around what this junction is, I've not dug into things, expecting I'm facing replacing the line from inside of FW down to fuel shut off, or possibly cutting a bit off the end and a new clamp or such.

Any typical history of what fails here?  In the little I looked it appears the T is steel and simply passing through a hole in FW, I could slide it fore/aft a bit, but with viewing distance and the fire sleeve over things, was not clear on everything.

Lastly, just filled the tanks last night, can I pinch off each of the down lines on the engine side of FW through the fire sleeve, say with a rubber tip squeeze vice grip clamp or something?  First step is managing the fuel shut off somehow.  Appreciate some tips, Darrell

 

[Tom Baker]

Yes, just a "T" fitting. The hoses slide over and some kind of clamp. Flight Design originally used a Band-it clamp there. I used to use an Oetiker, but now use a Norma screw type fuel injection clamp. I now locate the fuel filter between the "T" fitting and the "U" for ease of access for cleaning. The most common cause of a leak at this point is the wrong size fuel hose being used.

Yes you can clamp the fuel lines where they come out of the door post.

[GrassStripFlyBoy]

Clamped lines, drained fuel, and it's definitely on the cabin side of T, fire hose is soaked.  Now with the fuel leak under control I'm in decent shape, leaving on business trip for next week - glad I caught this now, could have been much more ugly.  Thanks much Tom

[GrassStripFlyBoy]

The hose does have a band-it clamp, I'm inclined to replace the hose / new clamps / relocate the filter - the band it clamp does not impress me so probably worth going through everything this side of FW while I'm into it.  What size hose is ideal for this run?  Thanks, Darrell

[Jacques]

1 hour ago, GrassStripFlyBoy said:

.  What size hose is ideal for this run?

Original hose (on mine) was Wurth  fuel hose 7.5 mm    some will say that 5/16'' would do ,  but that's 7.93 mm   . 

so, I ordered (locally) the Wurth when I did the hose change.

also,, I recently flown a CT with this modification ( which I like) : two(2) fuel filters on engine side of firewall , between the T and the A pillar outlets

[GrassStripFlyBoy]

Ok - its all apart and have made sense of things.  I'd like to shoot whoever did such a poor job of installing the band-its, I get these are tight areas to work in but they twisted off all the band-it ends so nothing was there to unfold and work back through, had to cut 3 of the 4 off.

Line is confirmed to be proper 7.5mm ID and both ends had taken a fair amount of compression set, the FW top feed end was loose to the T port, and clamp was placed in the smaller clearance land area.  I now have a better appreciation for dealing with a large port (fuel shut off valve) and the smaller T port, this line is tight to install on the valve, and slides over smaller T port about line to line size wise.

So I'll order up some new materials, about three hours to drain fuel, take everything apart, and make sense of what I'll be doing here.  Not too bad.

[Tom Baker]

For the 7.5mm hose this will work, https://www.ebay.com/itm/192199220787 .

[GrassStripFlyBoy]

Tom - thanks for the source on hose, hit the order button.  I purchased Norma S13's from partsklassik based off your previously shared "hose change order list", but didn't find a source for hose mentioned outside of FD or Airtime, and was thinking of just shortening the ends.  Now I'll have option to relocate filter, and with CI coming up next month probably will relocate it to have this done.

 

[Madhatter]

This is why I am going to all teflon lines and fittings with bulkhead fittings in the entire fuel system the same way as in certified aircraft. I will never have to replace them again. I also don't need the small filter behind the panel.

[GrassStripFlyBoy]

Madhatter - please keep a list of what you develop here, I'm a few years away from a hose change and would like to consider this update.

[Garrett Gee]

16 minutes ago, GrassStripFlyBoy said:

Madhatter - please keep a list of what you develop here, I'm a few years away from a hose change and would like to consider this update.

I second that sentiment.  Been looking at what all would be required for a few months now, but haven't made much progress.

[Madhatter]

It's a very easy project,  uses the same components used on certified aircraft. AC 43.13 as a reference.

I am also considering using a "Steve's Gascolator" in place of the CT original. It is much easier to service and pretty much crash proof. I put one on my cub and it's great. 

[FlyingMonkey]

4 hours ago, Madhatter said:

It's a very easy project,  uses the same components used on certified aircraft. AC 43.13 as a reference.

I am also considering using a "Steve's Gascolator" in place of the CT original. It is much easier to service and pretty much crash proof. I put one on my cub and it's great. 

I'd be interested in a list of parts & materials for this project.  I have a hose change upcoming in 2022.

[Anticept]

So I would still suggest the filter, madhatter, because it catches fibers. If you have an old floscan fuel meter, the fibers like to wrap around the impeller and jam it. First hand experience.

The red cubes I have not seen a jam yet, different impeller design, but might still be possible.

You can put the fuel screen before or after the fuel shut off, both positions are allowed.

There is one other mod I might suggest looking into. Try to get a fuel return line from the fuel tee back up to one of the tanks. Put a super tiny restrictor in it if you dont have one. Air will quickly purge from the system back to the tank, and I suspect the fuel pressure fluctuations during runup and takeoff will reduce to nothing because they'll purge the air being cycled around the system instead of sending it round and round until it finally gets purged out theough the carbs. I haven't done it personally yet because I've not identified how to get it up there yet.

[Madhatter]

I don't have a flowmeter. It is a choke point if you get debris in the fuel tank,  I have never seen any aircraft in 47 years with a small filter before a gascolator. I don't believe it would pass any federal approval for certified . Yes I understand there hasn't been an issue but I don't want to be the first, besides it's a pita and unnecessary for me.

[Madhatter]

2 months ago I have a friend who was flying a TL Ultralight Stream . It has a fuel flowmeter and totalizer. Both the totalizer and fuel gauge were wrong,  you guessed it, the engine quit. He dead sticked into a nice open field successfully.  Only one problem, it was in the middle of a military firing range. Now he has to deal with the FAA and the military

[Warmi]

1 hour ago, Madhatter said:

2 months ago I have a friend who was flying a TL Ultralight Stream . It has a fuel flowmeter and totalizer. Both the totalizer and fuel gauge were wrong,  you guessed it, the engine quit. He dead sticked into a nice open field successfully.  Only one problem, it was in the middle of a military firing range. Now he has to deal with the FAA and the military

That sounds rather incredible ( and frankly suspicious ) to have 2 completely independent systems fail at the same time… the gauge is mechanical and fuel meter is the usual red cube connected to Garmin G3x.

[Madhatter]

The aircraft guage  was defective, all small GA  aircraft fuel gauges are inaccurate, they should never be trusted on the low end. I never trust cheap fuel totalizers, you just don't need them on a small aircraft. If you put garbage in you get garbage out. You can see your fuel in a CT in flight, if don't see any you are SOL. It can't get any simpler than that. 

[Anticept]

Flowmeters/Totalizers aren't for determining if your tank is full or empty, they're for planning and efficiency. I find them useful, and are a decent secondary instrument for troubleshooting* too. If someone relies on them instead of reading the FUEL GAUGE to determine how much fuel is left, then that's just insanity.

* Lost my fuel pressure gauge on one flight in my old M20J, fuel flowmeter was normal for settings, determined it was a malfunctioning gauge. Still got landed, but it wasn't an emergency. Could have determined that none the less because the engine would have quit pretty fast, but the extra gauge helps assure.

* Had an engine start coughing on me, checked fuel pressure, good, checked flowmeter, it was abnormally high, landed ASAP. Bad floats.

P.S: the annoying rotax fuel pressure thing that can alarm on takeoff can be crosschecked with fuel flow too.

[Madhatter]

Most non professional pilots I know use the totalizer as a fuel guage.  I agree it's crazy. 

[Warmi]

11 hours ago, Madhatter said:

The aircraft guage  was defective, all small GA  aircraft fuel gauges are inaccurate, they should never be trusted on the low end. I never trust cheap fuel totalizers, you just don't need them on a small aircraft. If you put garbage in you get garbage out. You can see your fuel in a CT in flight, if don't see any you are SOL. It can't get any simpler than that. 

There is a huge difference between being inaccurate on the low end and being defective.

I have the same mechanical gauge on my Sting S4 ( same company as Stream ) and it has ben 100% reliable in the last 400 hours.
Of course, since I own the plane and are pretty much the only one fueling it, I run totalizer in my head ( basically I always know how much I put in and how much I have flown ) and use the gauge to confirm.

In any case, I never let it go below 1/4 ( which is about 5 gallons  ) and land it before that anyway ...

[FlyingMonkey]

I have to say I was not thrilled about sight tubes as my only fuel gauge in my CT at first, but I have grown to love them.  They never lie and they are always accurate (when properly calibrated and marked, and in relatively smooth air).  I don't love that there is a tube to the fuel tank that can fail, but I have never heard of that happening in a properly-maintained CT, and if it did the fuel should wick out between the wing and fuselage and stay out of the cockpit (except the smell of course).

The tubes have worked well for me for 8 years, and they are in great shape when I change them every two years.  They could probably go 5-6 years (if they were still readable), not that I'd test that.

[FlyingMonkey]

17 hours ago, Anticept said:

So I would still suggest the filter, madhatter, because it catches fibers. If you have an old floscan fuel meter, the fibers like to wrap around the impeller and jam it. First hand experience.

 

I agree, but maybe get the filter to the other side of the firewall, or one on each side coming off the A-pillar fittings?  I hate that the filter is a potential source of leaks right behind the panel.

Madhatter, do you have a source for the teflon hose, and an idea of how much would be needed?  I know this stuff is spendy, but since I'm doing the work myself and saving money there I would not mind making this change to avoid ever having to do it again.

Of course, you'd still have to replace coolant hoses (unless there are teflon hoses for coolant) and other rubber bits like carb sockets and engine mount isolators, but it would be a much less painful maintenance.

[Anticept]

A word of caution: teflon hoses need a different method of termination than rubber hoses to be reliable long term; use crimp on fittings or other teflon hose specific method. If you use the methods for rubber, the hose will very easily be damaged.

[FlyingMonkey]

1 hour ago, Anticept said:

A word of caution: teflon hoses need a different method of termination than rubber hoses to be reliable long term; use crimp on fittings or other teflon hose specific method. If you use the methods for rubber, the hose will very easily be damaged.

How does that work with things like barb fittings?  Do you need new connection methods, or some kind of end cap on the hose to prevent damage before going over the barb?