Thorp Air Command - T18.net

I can’t see the complete part number, it would lead you to the port size and thread.
Knowing if it is tapered or straight thread determines the fitting you should buy.
If tapered (NPT) use a pipe-to-AN nipple. Upgrade to hose; Put a hose end elbow on top of the nipple the B nut will let you clock the fitting.

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Scott Emery
EAA Chapter 326
T-18 N18TE

[/quote][/quote]

Right... so probably what he should have, unless the pump has a tapered pipe thread, is one of the o-ring fittings shown in my link, regardless of what is there now.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

It must be a straight thread to accept the bulkhead fitting so using John's recommendation would work great. I would bet the bulkhead fitting was used to reach the hard line coming to it since it is longer than a standard elbow. If a proper sized o-ring was used in the gap between the threads for the flared fitting and the threads for the jam nut, it may seal well enough to to keep using. It would take a fat o-ring. If it was mine I would use the proper fitting and make the fuel line to fit (either aluminum or hose). In fact, that is exactly what I did with mine when I redid my fuel system.

Of course this all hinges on the assumption it is the fitting leaking at the pump and not the flare on the tube dripping down on everything else. Cleaning off the blue dye may help locate any more leaks. Carb cleaner works great if you aren't concerned about any paint in the area.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Mark the area with chalk, the fuel leak should be easy to find.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

I haven’t had the opportunity to try it yet but a tip I stumbled across in another forum suggested using athlete’s foot spray because it is a white powder that sticks to what is being sprayed to locate oil leaks. I don’t know why it wouldn’t work for fuel too. Especially if the fuel doesn’t have blue dye in it.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

Thanks all for these suggestions, and in particular, the links to part numbers. That helps quite a bit.

I've been on travel so I haven't been able to get back to resolving this issue. More travel this week and next, so it will need to wait a bit longer.

Jeff, thanks for your insight on the turnbuckles. Sure it's not related to the fuel leak, but it's very helpful to have support identifying issues that I simply have not noticed. I'm a new aircraft owner and there are a lot of details in the system, so you pointing out the turnbuckle issue is great.

Thanks for the helpful suggestions. I was finally able to fix the leak yesterday.

It turns out the issue was a washer that was inexplicably placed between the AN elbow fitting and the fuel pump. Both have straight threads, as suggested here. There was an o-ring, but it's effectiveness was compromised by the ill-fitting, and thick washer. Somehow it sealed for 100 hours of flying, but finally started leaking. I removed the washer, replaced the o-ring, cleaned up the mating surfaces, reinstalled, and watched it for several hours.

Thanks again for the help, now on to other issues!

It turns out there's one more leak, but this one is from the bottom of the fuel pump, on the outlet port. The problem with this leak is that the AN fittings are hard to access.

1 - Is there a good way to remove the bottom AN fitting without removing the fuel pump? I can get the securing nut loose, but I still need to remove the fitting for the solid fuel line, then turn the elbow fitting to unthread from the pump. There's no easy access to the nut for the fuel line fitting under the pump.

2 - If the pump needs to come out, what's a good way to get it out? It's not obvious to me how to remove it without taking apart some of the surrounding structure.

3 - This new leak looks like it's coming from the fitting, but I've been reading the some Dukes pumps develop leaks. Do any of your have experience with Dukes pumps leaking? Did you end up fixing it yourself, get it overhauled, or get a different replacement? The pump is $1500, so there are a lot of things I'm willing to consider before getting a new one.

4 - How can I get the last half gallon of fuel out of the tank when draining it. Obviously the leak will end up self draining it. When I'm using a siphon, I end up with about an inch deep of fuel in the bottom of the tank. I bought a bulb siphon and another pump action siphon, but neither worked. Can I use a hand crank pump to defuel the last little bit from the tank?

5 - Should I be taking any specific safety precautions when defueling or fixing leaks? I end up with my head close to fuel fumes for longer than I would like. Would a respirator or similar help?

Thanks!

My aux fuel pump gave out on me last year so I feel your pain. You just gotta get down there, turned upside down, and take apart whatever you gotta take apart to get to it. There are fuel pumps out there for much less than $1500. I would check aircraft spruce for one that fits your specifications. When I worked on mine, I had an AN fuel plug I screwed onto the fuel line fitting. I did get a little fuel spillage while screwing on the plug. I didn't have an issue with fumes.

Disconnect the fuel line from the carb. Put a bucket under it. Turn fuel selector on. Done. Save the fuel in a sealed can. It makes a great solvent.
Cubes

Cubes, my airplane is fuel injected - does that make a difference? I suppose the point remains that I can use the built in pump and the single engine-side outlet to drain the last bit of fuel. Good suggestion, thanks.

Regarding pump choice,

I have two facet pumps on the airplane, one for each wing tank to pump fuel into the main. Can I use another facet pump in place of my Dukes (if needed). What makes the facet pumps 10x or more less expensive than seemingly all other pumps at Aircraft Spruce?

Your injection pump must put out around 28 psi. Engine pump puts out about 23 psi. Normal pumps put around 4 psi. Look up Airflow Perfomance. That's what I run.

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Bob Highley
N711SH
SN 835
KLAL

It doesn’t matter if it is fuel injected as far as draining the tank.
Does your plane have the full Airflow Performance system? In other words, do you have a flow divider, check valve, and return line all in one small area? This will most likely be right next to the aux pump. If so, you can use any car fuel pump that puts out in excess of 25 psi. The system will return the excess pressure. I’ve installed/replaced several aux pumps with $25 car ones. If you do not have the flow divider etc, you will need the same PN (pressure) you currently have.
Do this, remove your current pump and take it to a reputable auto parts store and ask for a replacement. When they ask what car it is off of, tell them it is an off road vehicle.
This all assumes that you know the pump itself is leaking.
Cubes

Lots of great advice here, but my favorite was "take apart whatever you gotta take apart to get to it"!

I had to remove both sides of the center tunnel and finally got to the fuel pump mount screws. Here's what I found when I finally got the bottom AN elbow off.



Another washer, inexplicably compromising the o-ring. This too survived 100 hours of flying. I removed the washer and installed a new o-ring, and now the fuel stays in the tank as desired.

The fuel pump was not the source of the leak.

While I was fixing this issue, I bought a new portable light from Ace. It is a wide angle, dimmable, USB rechargeable light that gets super bright and has several mounting options. It made a big difference to have good illumination.

I'm wondering about other options. What worklights do you guys recommend for working under the panel?

Work light under the panel ? I use a 6 year old with a Maglite !

RB