Fuel Selector Valve

[moontownMooney]

Anyone have a sense for how long the engine will keep running, when the fuel selector is turned to the off position? Stated differently, if I start to change tanks, how long do I have to turn the selector from one side to the other, before I risk starving the engine?

 

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[carusoam]

Moontown,  how long does it take to switch tanks using your fingers and your selector switch?

in other words...

Yes, from my first ride in the Mooney M20C...@ idle while taxiing, a couple of hundred yards...

Lessons learned...

• There is no both position in a low wing airplane... and
• if you can’t feel the detents, it is time to OH the switch...
• if you think it is good to do things without telling anyone, it’s not fair to surprise your CFI... 

A fuel injected Mooney doesn’t have a store of fuel like a carb’d engine does.  The carb bowl is what I ran a couple of hundred yards on.

Time to test your skills...

• Operating the selector valve on the ground.
• operating the selector valve at altitude.  (There is a procedure for this... It may include using the electric boost fuel pump...)
• running a tank dry at altitude, while observing fuel pressure oscillations (a hint of air bubbles).... a common fuel management technique for having all the fuel in the last tank...

things you want to know before you have non-flying passengers on board...

The engine will change sounds if it is not running, but it continues to turn.  It starts running again when the fuel shows up...

Read up on engine restarts in the air.  There are some things to be aware of to keep from over speeding and/or dumping fuel into the exhaust.... engine controls...

If you only take a second to switch the valve, even the engine instruments won’t even show anything happened...

PP thoughts only, not a CFI...

Best regards,

-a-

[McMooney]

I'd actually like to know also,  been a little slow once or twice reaching for that selector.

[carusoam]

Put it in the category of pulling the mixture to ICO, only you get less time at 2500 rpm and WOT.

does your POH have the procedure,for your plane?

To be slow to reach the valve, may indicate you have run a tank dry... this is where the recomendation of knowing the procedure comes from... probably something like... mixture out, switch tanks, fuel boost on, return mixture in, fuel boost off...?

the procedure keeps you from dumping a bunch of unburnable fuel into the exhaust before the engine fires up again...  not done properly can add expense to the broken exhaust...

PP thoughts only...

Best regards,

-a-

[Guest]

Fuel injected engines don’t run very long with the selector turned to “Off”, they only have the fuel in the lines and the strainer to draw from. Carbureted engines on the other hand have the lines, the strainer and the carburetor bowl to draw from before it quits.

If you want to know how long your engine will run, turn the selector valve to “Off” on the ground during your next run up.

Clarence

[201er]

Probably different on the ground at idle vs in the air at cruise fuel flow. How can the engine draw the fuel out of the line at all if the selector is off? Wouldn’t air or fuel need to be able to get in the line to replace empty space for it to flow at all? Does engine stop drawing fuel before the line is empty as a result?

[nels]

I did it accidentally on my maiden voyage in my J. I decided to switch tanks and without looking I figured the valve position was the same as my E which was all the way in one direction. The engine ran just long enough that my copilot and I were again comfortable and then the engine quite. What a scare but I quickly realized what I must have done. I figure it ran for about 30 seconds to one minute.

[Guest]

Yes it will run longer at idle, that’s why I suggested during “run up” the time would obviously be shorter at cruise power.  The amount of fuel drawn from a closed system will be dependant of the ability of the pump.  If you have fuel flow you will see it stop as well.

I do this test on every pre annual run up to test the selector.

Clarence

[air cooled dad]

Cruising around 9000’ on the way from Georgia to Michigan. Over the KaIamazoo airport I hit a big bump of turbulence just as the selector was traveling through the off position.  I drop my notched pvc pipe used to switch tanks. One potato, two potato three...engine begins to die. Woke my wife up.  She was mad. She got even more mad when I was laughing. Oops.  

‘75F

[McMooney]

yeah need to avoid the above.

my wife read another thread about fuel management, something about running a tank dry and decided she would have none of that.

first time that engine stops with her in it, might be my last day on earth.

[moontownMooney]

Cruising around 9000’ on the way from Georgia to Michigan. Over the KaIamazoo airport I hit a big bump of turbulence just as the selector was traveling through the off position.  I drop my notched pvc pipe used to switch tanks. One potato, two potato three...engine begins to die. Woke my wife up.  She was mad. She got even more mad when I was laughing. Oops.  
‘75F

This is the exact scenario I had in mind... how long did it run?

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[moontownMooney]

This is the exact scenario I had in mind... how long did it run?

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Sorry, I'm dumb, it's early, your potatoes were seconds... wow... that's not much time!

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[N231BN]

It's actually a pretty good idea to check how well your shutoff works. I have made it to the run-up pad in a twin Cessna with both fuel selectors OFF.