Fuel Selector Valve

[jasondepew]

Hi All,

The fuel selector valve in my 1950 C-170A has been leaking so we pulled it out during the annual. (With the valve in the OFF position, the gascolator re-fills over time.) There'd been some grit inside the valve that scored some groves into it. We polished them out some and put the valve back in, but it still leaks. I can't find a new valve anywhere. The IPM lists the valve as 04013020-3, with -4, -5 and -6 being associate parts that I'd be interested in.

Does anyone know where I can find one? MacFarlane said I can send it in and get it overhauled for $325. I don't know that they'd do anything we haven't tried and I'm not against just buying a new one if I can find it.

Thanks in advance!

Jason

[n3833v]

If it is the brass cone style, try lapping compound and mate together.

John

[Bruce Fenstermacher]

Jason, lapping as suggested is about all I can think you can do to the valve. Before I sen't it to MacFarlane I'd make sure they understand this is not the same valve found in B models which they sell a rebuild kit.

As for a new valve, there isn't any such animal readily available. There are some suspects that are close but no cigar. I will once again this year at Sentimental Journey next week, lobby Univair to get the valve they have for 140s approved for 170s but there seems little interest.

BTW Cessna's solution is to buy a newer style valve from them and approval for near $5000. That buys a lot of lapping compound.

Wish I had better news.

[jasondepew]

Sounds like lapping compound it is. Thanks for the info.

[imncntrl]

I need to figure out a new fuel valve as well. My last IA tried to fix it and told me never use it or it will leak again.

[Bruce Fenstermacher]

Jared, there are two schools of thought here. If you never use it, you will never shut it off and of course it won't leak. I'll go one step further. I think you should never fly your plane cause something will wear out or need maintenance.

I believe that when the valve sits idle in one position the valve builds up with particles which are the damaging culprit when the valve does get moved. In my opinion a valve that is clean, lapped in, moving freely, lubed with fuel lube and exercised, is better.

The key is maintenance and knowing the valve. And yes it is a pain and quite frankly I've yet to do it to my current 170. If the valve is in good shape you won't hurt it using it. If it starts to bind at all stop and disassemble and clean it.

Despite not having done recent maintenance to my valve I use it each and every time the plane is flown because our plane is parked on a hill and gas would run from one tank to the other and over flow if we didn't.

[bagarre]

BTW Cessna's solution is to buy a newer style valve from them and approval for near $5000. That buys a lot of lapping compound.

If your valve is not repairable and you can't find a direct replacement for a reasonable price, talk to your FSDO about upgrading the fuel system to the later setup. It's all Cessna parts approved for the next year model. Same airframe, same motor, same fuel line sizes... it might not be that hard to get a field approval.

You (or a mechanic) can pick up those fuel valves for a couple hundred bucks used if you search around it and make any fuel lines pretty easily.

[jrenwick]

After one experience of opening the hangar and finding that half my 170's fuel load had dripped onto the floor, I stopped ever parking a high-wing airplane without turning off the fuel. Marvel-Schebler float valves occasionally fail to seal after stopping the engine....

[DaveF]

Since I began turning the fuel selector to "off" when the airplane is in the hangar I've discovered that in flight my right tank feeds faster than the left. When I left the fuel on, the tanks would equalize before the next preflight. Now I have a new problem to solve.

[bagarre]

One of my tanks always feeds faster than the other. I think it's the right.
On a long flight, I just switch to the other tank after an hour or so to even it out.

[Bruce Fenstermacher]

In our 170s if the fuel valve is switched to off, the fuel tanks should still equalize through the valve but fuel will not flow to the gascolator.

The only way to stop fuel from equalizing between tanks is to put the valve one side or the other but of course then the fuel will flow from that tank to the gascolator.

[KS170A]

In our 170s if the fuel valve is switched to off, the fuel tanks should still equalize through the valve but fuel will not flow to the gascolator.

The only way to stop fuel from equalizing between tanks is to put the valve one side or the other but of course then the fuel will flow from that tank to the gascolator.

This is because the fuel flows through a "T" shaped passage way. When in the off position, looking down from the cockpit at the valve, the passages would look like a "T." When in the both position, the vertical portion of the T points towards the engine, like an upside down T. So as Bruce mentioned, whether in both or off, the Left and Right tanks are directly connected through the selector, and also shows why it's important to be in Left or Right when parked on an incline (one wing low), as the fuel cannot crossfeed through the selector.

[DaveF]

In our 170s if the fuel valve is switched to off, the fuel tanks should still equalize through the valve but fuel will not flow to the gascolator.

You mean, "In the 170 and 170A with the older style fuel valve ...", because that's definitely not the case with the B model fuel valve.

[bagarre]

EDIT: This post is wrong. The B model shutoff valve will not cross feed in the Both Off position.

That is the case with the B models as well.

Inside the valve is a cam that 'plugs' one of the 3 inlets at a time.

Fuel Both: None of them are blocked.
Fuel Left: Right inlet is blocked. Left inlet and Outlet to Gascolator is open.
Fuel Right: Left Inlet is blocked. Right inlet and Outlet to Gascolator is open.
Fuel Off: Outlet to Gascolator is blocked but Left and Right inlets ARE open to each other and they cross feed.

There is no position that shuts off both the left and right inlets at the same time.

[170C]

I agree with Bruce on his comments. I seem to remember George had an incident where he found fuel all over his hangar floor one time. I know we should turn the fuel valve off each time, but rarely do so. I would venture a guess that very few high wing planes would be found to have their fuel valves turned off while in a hangar or tied down on a ramp. Probably a potential disaster waiting to happen.