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Topic Options
#313497 - 11/13/16 02:17 PM Fuel selector rebuild
Turbofan Offline
New Member

Registered: 03/21/14
Posts: 11
Loc: Greenwich,ny
Mcfarlane says I need "special tools" for rebuild, anyone know what? My selector is suddenly gushing fuel so I'll be pulling it for rebuild, it's a 72 172L
Not paying 1800 for a new one

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#313501 - 11/13/16 03:07 PM Re: Fuel selector rebuild [Re: Turbofan]
Don Tedrow Offline
Platinum Pilot

Registered: 07/16/10
Posts: 3659
Loc: Bastrop, TX
The guys that I have seen do this make a little U shaped tool out of some coat hanger wire so you can compress the springs and washers enough to get the rest of the parts into the center bore. Your A&P or AI should know how to do this. You need someone to supervise and sign off anyway.
_________________________
1972 F33A Bonanza


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#313518 - 11/13/16 06:11 PM Re: Fuel selector rebuild [Re: Turbofan]
Showboatsix Offline
Gold Pilot

Registered: 12/04/10
Posts: 1816
Loc: KUAO, Aurora, Oregon
Originally Posted By: Turbofan
Mcfarlane says I need "special tools" for rebuild, anyone know what? My selector is suddenly gushing fuel so I'll be pulling it for rebuild, it's a 72 172L
Not paying 1800 for a new one


What year of aircraft, what model ?
I have done several and I have not needed any special tools other than a fine wire pick to pull the O-rings out of there capture grooves .
_________________________

Note: "Speed and 172 are not used in the same sentence!"


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#313524 - 11/13/16 06:32 PM Re: Fuel selector rebuild [Re: Showboatsix]
Joeman434 Offline
Diamond Pilot

Registered: 02/19/14
Posts: 6752
Loc: Ocala, Florida
72 L model...I know I have done several carefully without any special tools either. Sometimes I have just replaced the O ring on the selector stem and got away with it without pulling the valve completely out. I made a tool to push out the roll pin and re-install it with the valve in place. I know it's NOT the preferred way, but it gets the plane back in the air quickly since that is what usually leaks first.
_________________________
Do it right the first time.

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#313536 - 11/13/16 10:18 PM Re: Fuel selector rebuild [Re: Joeman434]
Showboatsix Offline
Gold Pilot

Registered: 12/04/10
Posts: 1816
Loc: KUAO, Aurora, Oregon

This is the repair kit from McFarland for your fuel selector valve, it is not a difficult repair to put these parts into your valve, I have done several it's easy to do and with a little bit of small air pressure you can test the valve for leaks if you want to. I have never had any leaks they have always been a positive shut off any A&P or IA should be able to do this with no problem at all.


http://www.mcfarlane-aviation.com/Produc...=FSO-KT-17&


Edited by Showboatsix (11/13/16 10:47 PM)
_________________________

Note: "Speed and 172 are not used in the same sentence!"


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#313543 - 11/13/16 10:46 PM Re: Fuel selector rebuild [Re: Showboatsix]
Showboatsix Offline
Gold Pilot

Registered: 12/04/10
Posts: 1816
Loc: KUAO, Aurora, Oregon
_________________________

Note: "Speed and 172 are not used in the same sentence!"


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#313551 - 11/14/16 08:08 AM Re: Fuel selector rebuild [Re: Showboatsix]
Flyer770 Offline
Safety Pilot

Registered: 07/30/16
Posts: 56
Loc: Oregon
Just curious, what pressure do you test at?

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#313552 - 11/14/16 08:18 AM Re: Fuel selector rebuild [Re: Flyer770]
Showboatsix Offline
Gold Pilot

Registered: 12/04/10
Posts: 1816
Loc: KUAO, Aurora, Oregon
You have very low psi just your fuel head pressure,
_________________________

Note: "Speed and 172 are not used in the same sentence!"


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#313553 - 11/14/16 08:44 AM Re: Fuel selector rebuild [Re: Showboatsix]
Skyblazer Offline
Pilot in Command

Registered: 02/01/15
Posts: 327
Loc: Texas
I've rebuilt parts of mine twice in the last year and a half. Just finished the second last week. Here's what I've learned.

In reference to your special tools...might be referring to tool to get the retainer / inner o-rings into the valve body. Bic highlighter cap supposedly works great...My a&p put the valve together without any special tools. Started with the center shaft install, then put both sides on. NOTE: The parts diagram shows the order of the small (expensive) retainer and inner o-ring backwards!

On the actual fuel valve rebuild there's great information on the Cessna 170 forum which I'd review once your valve is out.

I take the cowling off and drain the fuel from the hose going to the carb. While it's draining move your fuel selector and see if it shuts off fuel, etc. While the fuel is out it's a great time to spin off the wing sump drain's and replace those o-rings...I had one that was just starting to leak and when I got it out it was cracked really bad.

For access both times I took the seat stop out and pushed the seat as far aft as possible. I then took out the center console screws,removed two bolts with nuts that hold the fuel selector linkage, pulled back the carpet, removed the two inspection plates (hopefully you also have the small 1" plug too!), and then leaned in and unscrewed the fuel lines, then two screws and it's out!

Like Joeman said you might get lucky and just take the top off if you can get the pin out. My pin was really tight so I took the whole selector out and fabricated a punch out of a concrete nail after the IA's punch broke. That worked good. I replaced bad 0-ring on top and he fabricated a cork gasket and put it back together. I re-installed and he checked my work. Total cost - $0!! Just about six hours of my time. Hardest part was putting it back in. The second time my A&P buddy pointed out a 1" hole above where the screws that hold the valve to the frame in. Pry out the cover and you can put a long screwdriver down there and it's WAY BETTER than using the 90 degree small screwdriver that took a year off my life the first install!

I went to Harbor Freight and bought their service wrench kit for around $50. This will have the small, angled wrenches which will make holding the valve and getting the fuel lines on and off easier. These are good quality wrenches, but the case is cheesy. Also you might consider a magnetic nut driver extension that you can put a #2 phillips in. This makes putting the two screws that hold the valve in much easier. I used a small awl to line up one hole and then screwed in the other.
The service wrenches allow you to hold the fuel valve while turning the nut so you don't damage the aircraft by torqueing the fuel fuel valve...you can create a big problem!

Second time my valve was leaking from the outlet nipple o-ring which my IA didn't take off as it was so tight last year. I took it to my farmer/mechanic buddy who put a 6 point socket and 30" bar and gently broke it loose. Replaced the o-ring and problem half solved...the nipple also had corrosion/ding and wasn't sealing well. It's a $250 part from cessna...they take a AN919 fitting (few bucks), cut the nipple off at the end of the threads so it doesn't interfere with the fuel valve rotation, grind off the AN919, and sell it for $250. Luckily an old feller had the correct part acquired from Cessna stock that was sold cheap and gave it to me for free!! (love freebies!). You can also put a cheap sleave on it and hope it seals, but none of the old school mechanics recommended this so I passed and just replaced the fitting. Use a green scotchbright pad to clean corrosion off the fuel line seating surfaces and look for cracks that might be causing a leak.

McFarlane's kit is probably the smart way to go if you don't want to be doing it again for awhile...but you might enjoy working on it so much that you just replace what's broke and look forward to your next fuel valve removal! Like most jobs it easier the second time. Good luck!!

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#313558 - 11/14/16 10:19 AM Re: Fuel selector rebuild [Re: Showboatsix]
Shifty Offline
Second in Command

Registered: 06/01/11
Posts: 245
Loc: Florida
Originally Posted By: Showboatsix
You have very low psi just your fuel head pressure,


Water creates a head of 2.31 feet per 1 psi. Since fuel is lighter than water the head would be even less. Seems like the pressure would be in the neighborhood of 1.0 - 1.5 psi at the valve.

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#313626 - 11/14/16 09:45 PM Re: Fuel selector rebuild [Re: Shifty]
Showboatsix Offline
Gold Pilot

Registered: 12/04/10
Posts: 1816
Loc: KUAO, Aurora, Oregon
I personally think these should be overhauled every 5 years, I did mine after 18 years, and it still shut off ok, but the orings were extremely brittle, glad I did it this annual.
_________________________

Note: "Speed and 172 are not used in the same sentence!"


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