Fuel Sender Problem

[neilpilot]

If it does still not work, I am voting for a leaking float.

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Hard to imagine.  The float is new, although I realize new can still leak.  Even if it were leaking, you'd think that as I poured the 3 5-gal cans back into the tank, there would be an initial reading on the panel until the float leak took over.  And if it's leaking, then why get a full reading after I topped off?

 

On the other hand I have no other logical explanation.

[DonMuncy]

Make sure to let us know if you figure it out.

[Marauder]

Hard to imagine. The float is new, although I realize new can still leak. Even if it were leaking, you'd think that as I poured the 3 5-gal cans back into the tank, there would be an initial reading on the panel until the float leak took over. And if it's leaking, then why get a full reading after I topped off?

On the other hand I have no other logical explanation.

When you are grasping at straws, sometimes you need to grab them all. I chased an electric gear problem for a year to find the problem was a stupid slipping alternator belt.

Here is my logic on the float. If it is partially filled with gas, it would be low in the tank and may not be able to float at lower levels. When the tank is filled, the amount of air left in the float is enough to drive it to the top.

Think of it this way. Ever tried to take a beach ball and drag it underwater? The deeper it goes, the more it wants to floats. Maybe something weird like that is happening.

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[Bob - S50]

Here's my update.  With the sender removed used a boro scope to look for any obstructions; none found.  Then fished a string through the fuel filler and wing spar and tied it to the float, as N201MKTurbo suggested.  Pulled on the string to lift the (installed) float about halfway up and the panel reading moved smoothly between zero and half full.  The boro scope once again confirmed nothing holding the float down. 

 

So with the string removed (thanks N201MKTurbo!) we proceeded to add 15 gal of fuel, in 5 gallon increments, and the panel stayed on empty.  The same problem we reported earlier, even though there's no logical reason why the float would not float.  At that point, we decided to give up since we couldn't think of anything else to try.

 

After leaving the maintenance hangar, as I taxied to SS fuel the reading remained at empty.  Once topped, on the way to our hangar the panel read FULL, something it hadn't done since the O/Hed sender was first installed.  Since no actual repair was done, I'm not optimistic that the system is now functional.  If the weather cooperates, will test the system next weekend on the flight to Panama City's Mooney Summit.

 

N201MKTurbo gets the lunch (Larryb was a close runner up).  Thanks to all for your input.

 

woops - edited for correct winner (string-on-float idea was the winner)

Maybe it is the angle of the dangle?

 

If it eventually showed full, that tells me it eventually floated so it probably is not a bad float.  Have you checked to see if the float floats as you add fuel?  If not, maybe the angle it hangs at creates just enough binding that it won't float on its own.  However, using a string you were able to create enough pull to overcome the binding so it worked.

 

The other possibility would be if it is hanging at an angle the prevents proper internal contact.  Using the string may have pulled it over to a position that made the contact again.

 

Just thinking out loud.

 

Bob

[cliffy]

Have you thought about making a small tank and bolting the sender to the side of same and watching the sender as you fill the small tank? Any square can would do. Paint thinner can maybe. Cut out the narrow side and make a round hole in the bottom the same distance up as the sender sits in the tank. Some jumper wires and

the salvaged paint thinner to float the float and see what happens.

[craigsteffen]

Coming in late here.  Did this ever get resolved?

[neilpilot]

Our 6-pack cluster is the one with individual gauges that can be removed.  We swapped our fuel gauges with a used pair and now both tank levels work fine.

[bradp]

So it wasn't the motion of the (fuel) ocean after all.

[rqajpa]

Sir: I have a Mooney 20E with what I believe to be the same problem. Found that the sending unit float is 2 inches above the bottom of the tank. We have gone back to Mooney to make sure they have specified the correct part. If it is then we intend to report problem to FAA. 

[neilpilot]

2 hours ago, rqajpa said:

Sir: I have a Mooney 20E with what I believe to be the same problem. Found that the sending unit float is 2 inches above the bottom of the tank. We have gone back to Mooney to make sure they have specified the correct part. If it is then we intend to report problem to FAA. 

Roger, why would you "report the problem to the FAA"?  What's the purpose?  Is your M20E even registered?

[carusoam]

Rq,

I have read the entire thread...

What makes you think your problem is the same as what is in this thread?

Your float position is different than anything mentioned here.

The end result had nothing to do with the float or the sender at all...

 

If the FAA helps you find a solution, let us know how that works out...?

What makes MS really useful... a bunch of people sharing their ideas openly...

Tell us a bit about your challenge, we can help you find a solution.

Invoking the “I’m gonna tell the FAA on somebody” rule probably won’t get the help you want.

What’s next?

Best regards,

-a-

[Prior owner]

Rqajpa- The fuel indicating system is certified to indicate zero fuel remaining when the fuel level reaches the height where only unusable fuel remains.... so, two inches of fuel in the corner pocket of the tank wouldn’t be far off from that. I don’t see a problem here. If you think your float is too high, then it very well may have been inadvertently bent... and not a design issue. If the sending unit is new from the factory then it probably just needs to be adjusted?

many mechanics will set the float so that it reads empty while there is still some useable fuel remaining in the tank. Certainly better to read Low than high.

I haven’t checked the Mooney SM, but the aircraft probably has to be jacked to level or some other attitude while measuring unusable fuel level. Additionally, the end of the metal fuel line must be completely submerged in fuel, as the screen on the end of the pickup will not provide suction to draw fuel. 

 

Edited November 13, 2018 by PilotCoyote

[cliffy]

Here's Note #1 from the Mooney TCDS on unusable fuel weight for each model.

Note that there is a wide variance of unusable fuel by model. The B,C,D, E and F are the lightest unusable weight at only 3.4 lbs total between both tanks. 1.7 pounds per side is unusable, say maybe 1/4 of a gallon each side? 

NOTE 1: Current weight and balance report, including list of equipment included in certificate empty weight and loading instructions when necessary, must be in each aircraft at the time of original certification and at all times thereafter (except in the case of air carrier operators having an approved weight control system.) The certificated empty weight and the corresponding center of gravity location must include unusable fuel (not included in fuel capacity) as follows: 4 lbs. (+47.6) for the M20 and M20A; 3.4 lbs. (+48.4) for the M20B, M20C, M20D, M20E, and M20G; 15.0 lb. (+48.4) for the M20F and M20J; 48.0 lbs. (+48.59) for the M20K (S/N 25-0001 thru 25-0446); 18 lbs. (+48.59) for the M20K (S/N 25-0447 and ON); 36 lbs. (+48.43) for the M20L (S/N 26-0001 and ON); 36 lbs. (+49.23) for the M20M (S/N 27-0001 and ON) and M20R (S/N 29-0001 and ON) and M20S (S/N 30- 0001 and ON); 36 lbs. (+49.23) for the M20TN (S/N 31-0001 and ON).

[0TreeLemur]

On 11/13/2018 at 8:19 PM, cliffy said:

Here's Note #1 from the Mooney TCDS on unusable fuel weight for each model.

Note that there is a wide variance of unusable fuel by model. The B,C,D, E and F are the lightest unusable weight at only 3.4 lbs total between both tanks. 1.7 pounds per side is unusable, say maybe 1/4 of a gallon each side? 

 

I just had my tanks resealed and I learned that the location of the fuel intake tube in our aircraft is a variable.  Some of them are bent.  Some of them have finger strainers on them that are selectively plugged by sealant or other gunk.   This can result in some variance in the amount of unuseable fuel.  After a major electronics upgrade this past summer I drained the tanks to weigh it.   I ran one tank dry beforehand and when we drained it we got about about 0.6 gallons out of it.   I marked each side as 25.4 gal. useable.

[cliffy]

Did you level the airplane before draining or was it on its wheels?  

[Prior owner]

8 hours ago, cliffy said:

Did you level the airplane before draining or was it on its wheels?  

^^^ an important step, I believe...