Fuel Selector stuck in flight! M20K-231

[M20Kid]

I was flying my 1981 M20K-231 home after annual at DMax and was feeling pretty good about the world.  I was at FL180 passing over weather that most GA guys would have to fly hundreds of miles out of the way to get around.  This was the second leg of the flight and everything up to this point was working by the book.  I was flying on the right tank and reached for the fuel selector to switch to the left tank and - it wouldn't move!  I applied a pretty good force (but not so much that I thought I could break anything) but the selector would not budge.  I had plenty of gas as this was the first tank switch after departing the last fuel stop, where I left with full tanks.  I was passing near Albuquerque but heading towards a whole lot of nothing enroute to Mesa, AZ. I decided the prudent thing to do was divert to AEG outside of Albuquerque and get a mechanic to take a look.

 

To make this story shorter, the mechanic got in the airplane and moved the selector to all the positions.  When I tried it, I found that a much greater force than normal was required but that the selector valve could, in fact, be moved.  I didn't want to try that in the air, just in case the valve got stuck somewhere where that no fuel could flow and I had a glider.  Anyway, he took the cover off and found nothing obviouly wrong.  He applied some penetrating oil to help free up the valve and worked it around for a short time.

 

Since the remainder of the flight home was under 2 hours, I again filled the tanks and left for home.  I did switch tanks once during the flight and it was still much harder to move than ever previously.

 

Has anyone else experienced this same issue?  It feels like something is gumming up the valve.  Is there anything in there that could come loose and cause this issue?

[gsxrpilot]

I had the very same issue over the top of weather in the Arkansas/Oklahoma/Texas corner. Mine had been difficult to turn ever since I bought the plane and  so I made a handle out of PVC that allowed me to generate more force and have better leverage.

 

So there I was over the top of the weather and went to change tanks. I couldn't get it to budge. I also decided to divert, but just for more fuel. I figured worst case scenario, I'd just use the one tank until I could get home to my mechanic who is Don Maxwell. I diverted but then kept trying to move the selector. I got the tanks switched before actually landing so, then with a full fresh tank, decided to continue the original course.

 

The next time the plane was at Don's, I asked him to fix the fuel selector. After his rebuild of the valve, it's now an easy fingertip task to switch tanks. I could even send you my special handle as I don't use it anymore.

[ELT]

I had a selector in a C jam in the off position as you must pass through off to go from left to right tank.  Result was an off airport landing.  I check the selector in my E with religion.

[jetdriven]

I don't know when I started the ritual but before starting up I move the fuel selector to all positions including off just to be sure it's good. Then I select the fullest tank and start up. It might be water freezing up in the fuelselector. A tiny drop frozen could jam the fuel selector.

[Awful_Charlie]

It is exactly that sort of thing that makes me plan to change tanks when within easy gliding range of an airport, particularly before I do a water/mountain crossing - having changed I'm sticking with that tank until I get in gliding range the other side! I'm moderately terrified of changing tanks and having the knob come off in my hand!

 

Never had it happen yet, but a little forward thinking will hopefully prevent an incident becoming a crisis

[Rhumbline]

Ditto.  It's a sensible practice.

[Jeff_S]

I think it was just karma getting back at you for being so smug in your choice of cruising altitudes.

 

[pirate]

I had a similar problem several years ago so I had laser rebuild mine, perfect ever since.

[aviatoreb]

Wow that is a scary failure mode that never occurred to me.  That is sort of an argument against running your tanks dry for maximum range lest on sputter when you switch you find you can't switch.

 

Is there a maintenance strategy to prevent this thing from sticking that has stuck for several of you?

 

Suppose one is really back against the walk with a dry or almost dry tank and fuel in the other but a stuck valve.  Based on what I read above I am inferring that the best strategy is to use brute force to try and move that lever if it gets stuck since at that point there is not a lot to loose and it might work.

[aviatoreb]

It is exactly that sort of thing that makes me plan to change tanks when within easy gliding range of an airport, particularly before I do a water/mountain crossing - having changed I'm sticking with that tank until I get in gliding range the other side! I'm moderately terrified of changing tanks and having the knob come off in my hand!

 

Never had it happen yet, but a little forward thinking will hopefully prevent an incident becoming a crisis

 

Right after my PPL I read a super book called "After the Checkride" by a 50,000 hour pilot named Fried - great book full of interesting stories and wisdom.  He says he does one more than you.  When he is crossing hostile terrain like water, he doesn't touch anything.  Not power setting, nor prop nor mixture since he says if something goes bad it is often during a change.

[jetdriven]

Wow that is a scary failure mode that never occurred to me.  That is sort of an argument against running your tanks dry for maximum range lest on sputter when you switch you find you can't switch.

 

Is there a maintenance strategy to prevent this thing from sticking that has stuck for several of you?

 

Suppose one is really back against the walk with a dry or almost dry tank and fuel in the other but a stuck valve.  Based on what I read above I am inferring that the best strategy is to use brute force to try and move that lever if it gets stuck since at that point there is not a lot to loose and it might work.

 

Sure,  if you notice any difference in the friction of the fuel selector, investigate. I have a hard time believing that a fuel selector was working great the first leg and somehow jams the second leg, save for water in the fuel that freezes. But still, monitor any water you find and get it all out.  Water can kill in those turbo airplanes that fly at cold altitudes.  Also, verify you can reach all the tanks before choosing to run one dry.

 

I flew with a guy in a 201, we drained a quart of water from the left tank, and we had just been flying and doing maneuvers on that tank.  Be vigilant.  That could have ended up badly.

 

But seriously, that thing should be free and have detents in all positions. Monitor this. Ours began to get slightly tight and it was leaking upon removal, I ordered a kit from LASAR and completely rebuilt it.  Smooth again, and no air leaks introduced to the fuel supply.   Another thing be sure no screws or coins fall into the well on a 1978 and older Mooney. They can jam the fuel selector as well.

[KSMooniac]

One of the biggest benefits and safety improvements that comes with owning a plane is knowing it well enough that when something changes, YOU notice it and can investigate it.  The fuel selector should be very easy to turn, with positive detent action at all 3 locations.  The maintenance manual calls for period lubrication to help keep it functioning properly.  If you need a tool to turn it, then it ain't right.  Get it fixed!

[carusoam]

On the topic of detents....

My fully worn 65 C had no discernible detents...

The newer O has more of a feel of clicking into place.

Are the older valves supposed to feel like they have detents?

If they don't, is that the sign of wear we should be looking for?

Best regards,

-a-

Apparently Scott from Kansas has answered my question hours before I typed it...

[aviatoreb]

 Water can kill in those turbo airplanes that fly at cold altitudes.

 

We aren't talking about a turbo issue here are we?  We are talking about cold issues.  The high here tomorrow will be -5F on the ground.  Freezing water issues plague NA airplanes too in cold climates.  Or were you talking about something engine?

 

 

Sure,  if you notice any difference in the friction of the fuel selector, investigate. .. Also, verify you can reach all the tanks before choosing to run one dry...

But seriously, that thing should be free and have detents in all positions. Monitor this.

 

Agreed.  Test both tanks is part of my preflight check list.  I always figured I was testing the integrety of the fuel flow.  I now realize I was also testing the switch itself.

 

Someone else said it and I agreed.  This is one of the sort of issues where having ones own airplane is a safety advantage since any minor changes like a change in friction of the fuel selector can be easily detected by memory and addressed hopefully before it gets worse.

[aviatoreb]

I was flying my 1981 M20K-231 home after annual at DMax and was feeling pretty good about the world.  I was at FL180 passing over weather that most GA guys would have to fly hundreds of miles out of the way to get around.  This was the second leg of the flight and everything up to this point was working by the book.  I was flying on the right tank and reached for the fuel selector to switch to the left tank and - it wouldn't move!  I applied a pretty good force (but not so much that I thought I could break anything) but the selector would not budge.  I had plenty of gas as this was the first tank switch after departing the last fuel stop, where I left with full tanks.  I was passing near Albuquerque but heading towards a whole lot of nothing enroute to Mesa, AZ. I decided the prudent thing to do was divert to AEG outside of Albuquerque and get a mechanic to take a look.

 

To make this story shorter, the mechanic got in the airplane and moved the selector to all the positions.  When I tried it, I found that a much greater force than normal was required but that the selector valve could, in fact, be moved.  I didn't want to try that in the air, just in case the valve got stuck somewhere where that no fuel could flow and I had a glider.  Anyway, he took the cover off and found nothing obviouly wrong.  He applied some penetrating oil to help free up the valve and worked it around for a short time.

 

Since the remainder of the flight home was under 2 hours, I again filled the tanks and left for home.  I did switch tanks once during the flight and it was still much harder to move than ever previously.

 

Has anyone else experienced this same issue?  It feels like something is gumming up the valve.  Is there anything in there that could come loose and cause this issue?

 

Did it go from nice and buttery smooth one day to stuck the next or did it progress until stuck?

[Jerry 5TJ]

There are many failure modes.....I had the fuel selector stick in my "E" years ago.  

It was a fine winter day, bright sun glistening on new-fallen snow....etc

It was clear and cold; perfect VMC.   I used engine pre-heat and went flying. 

After about 30 minutes of flight I tried to switch tanks: Not possible -- some slush from my shoe had gotten into the "cup" and frozen solid. 

I landed without any problem.  

And after that, I positioned a floor matt over the fuel selector except during flight.

[BKlott]

My first thought was the cold temperatures at high altitude. The switch handle is in the cockpit floor but the valve itself may be exposed to a far different temperature environment. Just a thought.

[flyboy0681]

One of the biggest benefits and safety improvements that comes with owning a plane is knowing it well enough that when something changes, YOU notice it and can investigate it.  The fuel selector should be very easy to turn, with positive detent action at all 3 locations.  The maintenance manual calls for period lubrication to help keep it functioning properly.  If you need a tool to turn it, then it ain't right.  Get it fixed!

 

 

This is a very true statement. Not only do I know how she should feel, but sound too. Two years ago after starting up and sitting there idling I thought I heard a really low frequency sound that my partner didn't hear. I didn't want to take any chances and cancelled the trip. Later that week my A&P investigated and it turned out to be the vacuum pump on its last legs.

[Marauder]

One of the biggest benefits and safety improvements that comes with owning a plane is knowing it well enough that when something changes, YOU notice it and can investigate it.

So very true Scott! I noticed in August that my TAS was showing 4 or 5 knots less than I have been seeing it. Thought I was dealing with a power issue and downloaded the engine data to the Savvy guys. Their comments were that everything looked great.

During the Fall, I learned to live with it, but it still was troubling me. Come December, during my IFR cert, they tell me I have a leak in the pitot system. Ah ha! That would explain it!

[M20Kid]

Thank you to everyone for all the great feedback!  My first thought at the time was water freezing; I had just been in trace icing and decided to climb to FL180 to get to blue sky.  I still though ice was perhaps the culprit and turned on the cabin heat a little extra - the heater blows out right over the top of the fuel selector valve.  The ice theory went away when the problem remained after sitting in a warm hanger with the mechanics for over an hour.  Also, on the remaining flight home the valve was still very stiff.  Had I not seen it turned on the ground, I'm sure I would not have put enough force to move it in the air.

 

From what I've read here, it appears the best course of action is to have that valve rebuilt.  It has always operated easily and smoothly until it failed to move at all, which seems to clearly indicate something coming apart and blocking the action.  I'll have someone open that valve and find the cause of the sudden change.

[M20Kid]

Some additional follow-up information.

I've researched the valve and been told there is no rebuilt kit available and a replacement is over 1.7 AMUs!  Not the place I want to start.  After researching the valve further, it appears to be fairly bulletproof.  The inside chamber is polished smooth and so would be difficult to 'jam' with anything coming through the fuel lines.

 

My current understanding is that the valve has some external springs and arms that are not visible until removing the belly skins.  While I have not removed the belly (I do not have the luxary of a one-piece belly) I imagine it would be possible to get ice on the moving parts.  As I mentioned in my original post, I had picked up some trace icing during the climb and I did see some snow before leveling off in the blue sky above; OAT at FL180 was -15C.

 

My question is - could moisture have gotten inside the belly skins and frozen on the valve mechanism?  Sitting in a MX hangar with the belly skins still attached may have provided enough insulation that the ice was only partially thawed when the mechanic was able to move the selector.  My situation today is that the selector feels relatively normal now sitting in the hangar in Phoenix.  I'm not one to spend money unneccessarily but I want a safe airplane, too.

 

Any thoughts?

[chrisk]

I have not looked at this part in detail, but I have always assumed there are some "O" rings in there. I can imagine one of those coming apart and causing a jam.  Presumably the O-ring parts would be caught down stream....

[slowflyin]

I've never had this issue with my Mooney but I had the same thing happen with my C170.   Smooth as silk to stuck!   We disassembled the valve, cleaned, smoothed if up and applied "EZ turn".   Very sticky stuff.   On tube should last at least a dozen lifetimes.   Spruce sells it.  I have not been in my Mooney valve but I assume they are very similar.

[larryb]

I would take it out, take it apart and inspect. No other way to know what you are dealing with. It won't fix itself.

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