Fuel valve rebuild and manual mistake WARNING

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

Post Reply
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Fuel valve rebuild and manual mistake WARNING

Post by Bruce Fenstermacher »

I just got done rebuilding my fuel selector valve. I have the newer valve found in the B model shown on page 106 of the 170B parts catalog. It is the valve that is machined out of square stock as opposed to the older one that looks like it has a forged body.

WARNING
Looking at my valve while I disassembled it and reviewing Fig 64 on page 106 of the parts catalog I realized that the position of the inner o-ring #16 fig 64 is shown on the wrong side of the retainer, #17. I confirmed this by looking at page 13-17 figure 13-9 in the 100 series service manual '62 and prior which shows the o-ring in the proper place.

FYI the parts you will need to rebuild this valve are:
(moderator note: WARNING: this parts list is incomplete. See/Read the NEXt where Bruce caught the error)
2 - o-ring MS29513-012
2- o-ring MS29513-116
1- o-ring MS29513-111
1- o-ring M83248/1-010 (added per next post, moderator)
1- Gasket Cessna #0513125

If you are careful you may be able to reuse the cork gasket if it is in good shape or you could make your on new one from very thin gasket material.

Total time to defuel the plane remove, dissassemble, rebuild and reinstall valve was about 3 hours with one person. The valve is a little bit of a pain to get out but and back in to the plane but no where close to the worst job I've done. Rebuilding of the valve is easy and straight forward. Just be careful on disassembly as there are several little ball bearings to lose.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

I forgot an o-ring - A complete fuel valve parts list

Post by Bruce Fenstermacher »

My appologies. I forgot one of the o-rings in my previous post. So much for proof reading. :roll:

Complete fuel valve rebuild parts list for newer machined fuel valve found in B model and some A model 170s:

2 - o-ring MS29513-012
2- o-ring MS29513-116
1- o-ring MS29513-111
1- o-ring M83248/1-010
1- Gasket Cessna #0513125
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
jon s blocker
Posts: 217
Joined: Tue Apr 23, 2002 1:56 pm

fuel selector valve rebuild

Post by jon s blocker »

Bruce,
Where did you order your seals and gaskets from? Did they have the required parts in kit form? I'm in the process of rebuilding mine and appreciate the heads up and parts information.
Thanks, Jon B
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

fuel selector valve rebuild

Post by Bruce Fenstermacher »

I gave the o-ring numbers that the cessna part numbers cross reference to. The 29513 rings although some what common are the same as other more common rings which I can't remember the number (according to the Parker 0-ring cross reference guide.) I'm not sure if the M83248/1 will cross to any thing. I got all the o-rings from a local mechanic friend who had them in stock. I reused the cork gasket although I could have and would have cut my own. Total cost to me for the rings was $5.00 and the mech. actually reassembled the valve cause he was curious how it worked. You shouldn't have a problem getting the gasket from a Cessna parts dealer except it's only about $2.50 and most have a minumum order. You will also want a small dab of fuel lube and this is very expensive stuff so befriend a mechanic that has some.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Post by GAHorn »

The illustrations in both the IPC and the Service Manual are identical illustrations. But the nomenclature of the two items in question is CORRECT in the Service Manual and incorrect in the IPC.
For those in possession of the IPC only: Page 106, Figure 64, item 16 SHOULD BE:
PN 0513120-4, Retainer

Item 17 SHOULD BE:
PN AF934-7, O-ring (superceded to new PN MS29513-012)

If you use the above info to correct your IPC, it should solve the problem.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Post by Bruce Fenstermacher »

Hey George better have those glasses checked. :D :D

What you say about switching the nomenclature in the IPC is correct and doing so as you describe will get the parts in the correct order.

However the illustrations are not the same if you look close, at least mine aren't. I have the McCurtian CD with both the IPC and the Service Manual and a hard copy of each the IPC dated September 1, 1956 and the Service manual dated February 1, 1962.

The IPC in each case clearly shows (right to left) the large ball[18], then the metal retainer ring(17). The o-ring (16) next to the retainer then the small ball (15). The order of the metal retainer and the o-ring are reversed from what they should be. If you don't read and make the corrections to the text you note, but simply look at the picture to identify the parts order it will not work and will leak fuel. I know first hand.

The Service Manual picture and nomenclature are correct having (right to left) the large ball(17), the O-ring(16), the metal retainer(15) and the small ball(14).
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Post by GAHorn »

I have the same revision status as you, but at the risk of even more confusion...
I posted my earlier message exactly as I did in order to alleviate possibilities of error. The problem with the revision status of thes publications is that "revision" dates and "printing" dates no longer have relevance. (The manuals are public domain and anyone can print them as much as they wish.) The result is that print quality varies, even among the Univair reproductions such that details of illustrations can be pretty muddy. The retainer, IPC item 16 (which is incorrectly labelled "O-ring") appears as a dark circular object as an O-ring might. The actual O-ring, IPC item 17 (incorrectly labelled "retainer") appears as a lightly-colored, multiple-step object much as a metal retainer might appear.
The correctly labelled Service Manual illustration also shows the retainer as a dark object and shows the O-ring as a light-colored object.
I suspect that poor print quality caused the editor of the IPC to mis-label the objects. The Service Manual illustration is slightly better quality, but can mislead the viewer as well.
In any case, the correct order of the parts is, from valve body outward: small ball, retainer, O-ring, large ball, spring, large O-ring, nipple.
It may help to realize the function of the parts. The small ball operates as a transfer mechanism to transfer motion from the fuel-handle lever's cam. That small ball acts against the larger ball to move it away from it's seat (the O-ring.) That larger ball is actually a check-valve, and when pressed against it's seat (O-ring) by spring pressure, it prevents the flow of fuel from the nipple towards the central area of the valve-body. When the lever/cam is moved against the small ball, it in turn pushes the large ball away from the O-ring allowing fuel to flow. Subsequently moving the lever/cam away from the small ball, allows the spring to push the larger ball back against the O-ring and shutting off the flow of fuel from that tank.
If the retainer (which merely holds the O-ring in position) and the O-ring were reversed (such as the text of the IPC would lead you to do) then the fuel would never shut off because the larger ball would never seat against the O-ring. This is a sometime problem that owners of freshly-rebuilt valves occasionaly present when they or their mechanic have followed the incorrectly labelled IPC without understanding the actual workings of the device. :?
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Post by Bruce Fenstermacher »

gahorn wrote:The illustrations in both the IPC and the Service Manual are identical illustrations.
George you said the illustrations were the same. They are not although they could look the same when viewing a poorly reprinted copy as you point out. I am lucky enough to have 2 very nicely printed original manuals that show this clearly when looked at closely.

At the time I rebuilt my valve I only had the McCurtian CD and after doing it wrong following the McCurtian CD IPC, I figured out how the valve worked and realized what seemed to be a mistake in the IPC. Before I just installed the valve parts "my way", I reviewed the McCurtian CD Service Manual. I could clearly see because I was looking close at the pictures that the IPC was wrong and the Service Manual was different and was right. My next move was to inform everyone here with my original post.

I think we've pretty much beat a dead horse here. :D
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Post by GAHorn »

I'm glad you pointed this situation out, Bruce. It's going to save someone a lot of grief.
At the risk of further massacreing the dead horse,...YOUR McCurtain CD illustrations might appear different and your original printed manuals may also be more clear. The more commonly available replica Cessna illustrations that I have are virtually identical, and I just thought it worthwhile to point that out to anyone who might own re-prints. I completely agree that print quality is likely an issue. McCurtain probably developed their pdf files from Cessna microfiche and may have enhanced the art-work. Might be a good argument for their product over the Univair reprinted Cessna manuals.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
N2255D
Posts: 489
Joined: Wed Apr 24, 2002 3:42 am

Post by N2255D »

I had to rebuild my fuel selector and had all the seals but no gasket . I tried getting it from Cessna and it was a reasonable $5.10. The only unreasonable thing was they had to be bought in lots 10. My gasket was in good shape so I'm Going to see if it will last another 52 years. If you need to take one apart be careful with the gasket or find some other people withe leakinkg selector valves.
N170BP
Posts: 552
Joined: Mon Jul 22, 2002 7:24 pm

Post by N170BP »

I was able to buy the gasket in question (just one) from
Spanaflight in Puyallup, Washington State. As I recall,
the price was roughly the same (a few bucks....).

Bela P. Havasreti
'54 C-170B N170BP
Dave Clark
Posts: 894
Joined: Mon Apr 22, 2002 6:25 pm

Post by Dave Clark »

I think Sac Sky Ranch has them in onesies too.
Dave
N92CP ("Clark's Plane")
1953 C-180
User avatar
Gary
Posts: 82
Joined: Thu Jul 03, 2003 12:32 pm

Fuel Selector parts dealer

Post by Gary »

I just rebuilt my selector as it was leaking. It is a job to get the valve out as it is hard to get a wrench on the bottom nuts holding the valve in place. I called Sac sky ranch and he didn't have the o-rings but gave me a number to try. El Cajon Aircraft Supply 1 800 888-3227. He had all the parts and yes, I could buy only one of the gaskets. His price for the gasket was $3.94. I ordered double the parts to have a spare set. The price with postage ($1.00 as I asked him to just put it in an envelope and send it US mail) came to $14.40. So one set was only $6.70. I ordered on Friday and had them Monday in the mail. This was April 2004. It is nice to have a valve that doesn't leak.
GARY 1909C
User avatar
n2582d
Posts: 2808
Joined: Mon Apr 29, 2002 4:58 am

Fuel Valve O-ring

Post by n2582d »

Bruce,
I'm in the process of rebuilding my fuel valve. Thanks for the work in updating the o-rings to current part numbers. I'm curious where you found p/n M83248/1-010 as a superceded p/n? Is this for the shaft o-ring shown in fig. 64-7? The p/n in the book for the shaft o-ring is AF934-5. This has been superceded to MS29513-10 in Cessna's 27 January 1995 parts catalog revision sheet. Are M83248/1-010 and MS29513-10 two numbers for the same o-ring?
Gary
User avatar
Bruce Fenstermacher
Posts: 10313
Joined: Tue Apr 23, 2002 11:24 am

Post by Bruce Fenstermacher »

Gary it was quite some time ago that i did that and I don't recall nor will I have a record of where I came up with that number.

My method at the time was to use various online resources such as CessnaParts.com to cross reference to AN or MS numbers. It is likely that I got an AN number then using a different cross reference came up with that MS.

There are two possibilities here. 1. I messed up. 2. Both MS numbers are for rings that will work with the difference being the compound the ring is made of and both being suitable.

I'll do some research later and post back but in the mean time I'd go with the number you came up with.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Post Reply