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Derek

Did I break something already?

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I was fueling my new to me m20j. I was with my CFI. It was actually my first time doing self-serve fuel. I guess I must have screwed up because when I got back in the plane left tank gauge was 0 and the annunciator for fuel was on. Is it possible that I damaged something sensitive with the pump? Thought I was being careful... maybe not careful enough.

At any rate at least I got another two hours down of the insurance probation.

Thanks!

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There is 2 senders, one inboard, and the other outboard, the inboard is protected by a rib, IIRC you can see the outboard arm. Either way unlikely both were damaged, I’d guessed a wire got knocked off at the inboard sender (they are in the footwell of the rear seats), maybe already fragile connectors got broken by luggage or a foot kicking the sender area.


Tom

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If the outboard sender were damaged it would only effect the quantity on the more than half full side of the gauge. 

If the inboard sender fails to move with the fuel addition it could be several issues.

1. the float is stuck and some bumpy weather might free it.

2. the float does not "float" anymore and stays down immersed in the fuel instead of on top of it. 

3. the wires between the senders are corroded and increasing the resistance. 

It is NOT possible for you to damage the senders by filling the tanks. 

did your CFI continue to fly with you after the fuel gauge failed to indicate?

do you have the sight gauges set in the top of the wings.?

 

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3 hours ago, Cruiser said:

did your CFI continue to fly with you after the fuel gauge failed to indicate?

Yes. We flew on that tank as well.

 

4 hours ago, Cruiser said:

do you have the sight gauges set in the top of the wings.?

 

Yes and that side indicates true.

Is there anything I can do to diagnose the problem before talking to the shop?

 Thanks!

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Point the nozzle outboard on each side away from senders.  Always stand there and tell the fuel guy the same thing in a very nice way. 

5 hours ago, Cruiser said:

It is NOT possible for you to damage the senders by filling the tanks. 

I don't agree with this statement.  There is sufficient pressure in some fuel trucks to do damage.  At a self serve pump--not so likely.   @PT20J could probably give you a good place to start.  Try him. 

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The inboard and outboard senders are floats attached to rheostats that are wired in series. If the outboard sender has a bad spot on on the rheostat near the full position, it might cause this when you filled the tank. Try running off that tank and see if it comes back alive when the fuel level drops. 

Skip

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Sounds a lot like a stuck float that didn’t float back up when the tank was filled...

Lets start with the easy stuff first...

Look in the tank, find the floats...

Start with the empty tanks first...

See if you can exercise them...

But... if looking for a reason to get those digital fuel floats... 

:)
PP thoughts only, not a mechanic...

Best regards,

-a-

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Sounds a lot like a stuck float that didn’t float back up when the tank was filled...

It would have to be 2 stuck floats to get the fuel warning/0 reading, highly unlikely. I’m going with broken wire going to inboard sender.

 

 

Tom

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bummer...

look for two stuck floats..?  :)


The two floats are wired in series, combining their results...

Ground, variable resistors, logic box, display and light, voltage supply...

Find the wiring diagram... To see if A single broken ground wire can be causing this result...?


unlikely to be anything done by filling the tank...

Were they working anytime before?

PP thoughts only...

Best regards,

-a-

 

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9 hours ago, KB4 said:

Point the nozzle outboard on each side away from senders.  Always stand there and tell the fuel guy the same thing in a very nice way. 

I don't agree with this statement.  There is sufficient pressure in some fuel trucks to do damage.  At a self serve pump--not so likely.   @PT20J could probably give you a good place to start.  Try him. 

I concur. I don't remember if it was here or during my checkout, it was suggested to me to angle the nozzle towards the outboard portion of the wing. Mainly to protect the sight gauge float from damage.

Brian

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6 hours ago, Vno said:

suggested to me to angle the nozzle towards the outboard portion of the wing.

If I recall correctly I was doing the opposite and was fueling towards the inboard side.

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8 minutes ago, Derek said:

If I recall correctly I was doing the opposite and was fueling towards the inboard side.

It is just technique, but the angle is very slight. Just don't shoot the fuel directly onto the sight gauge float. Or any float for that matter. It will be self-correcting when the fuel starts splashing back out of the fill. You can see into the fill quite a bit so it is easy to find a point where the fuel stream is not hitting anything sensitive.

Brian

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On 11/2/2019 at 9:19 PM, Derek said:

Yes. We flew on that tank as well.

 

Yes and that side indicates true.

Is there anything I can do to diagnose the problem before talking to the shop?

 Thanks!

the outboard sender is accessible from one of the inspection plates on the bottom of the wing. Use a multimeter set to OHMs and measure the resistance between the center stud and the flange of the sender. It will be 1 or 2 ohms when the fuel is below the sender float level and up to a maximum of 30 ohms when the tank is full. 

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The inboard sender is to the cabin side looking down the filler from the front of the wing.   Without blowing yourself up, use your fuel measuring stick to see where it is.  A flashlight should also be useful for looking around down the fuel filler.   be very careful with seating the caps.  If they are adjusted properly (you replaced the o rings right) It should be a slight snapping action to get them down.  Line guys will pound them down and break the ears off.

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33 minutes ago, Yetti said:

Without blowing yourself up

Oh boy.

34 minutes ago, Yetti said:

use your fuel measuring stick to see where it is. 

Don't have one of those, but I assume you mean to feel around with a stick?

 

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Unless you have on the wing gauges a fuel stick is the only reliable way to not make your Mooney a glider at an inopportune time

lots of threads on how to create one.

Heavy Duty paint stirrer from Sherwin Williams.   Sharpie. Draw a line.  Fill the tank to the top.  Do the math.

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2 hours ago, Yetti said:

Unless you have on the wing gauges

Fortunately I have those. I do plan to make a stick though.

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22 hours ago, Derek said:

If I recall correctly I was doing the opposite and was fueling towards the inboard side.

I point the nozzle inboard to keep it from splashing out.  I recall on one side, one of the floats can get hung up on the nozzle if you point it inboard, so you have to watch out you don't bend it.  An LED headlamp is handy to help you see in the fuel tank when it's poorly lit.

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speaking of fuel senders.....

If anyone has an old one lying around, I need the float off one for a project I am working on. 

 

 

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Tom,

Check In with Alan for all Mooney related parts... @Alan Fox

He can saw you up Mooney to meet your specs...or he may have one already sawed up...

Scott in Kansas May have parts from his spare J as well... if the float needs to be specific to a particular model...

Best regards,

-a-

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@Derek:

Your plane should have 2 sensors. They are wired in series, so they together form a resistor between 0...60 ohms.

The outboard sensor is connected to airframe with its body (=grounded). The other wire goes to THE BODY of the inboard sensor. The sensor itself must be isolated from the airframe.

Otherwise your fuel gauge will show only half full tank! Technically the outboard sensor is disconnected from the circuit. This happens easily by losing the wire from the outboard sensor OR  NOT USING PLASTIC SHOULDER WASHERS!!!!!!!

The center pole/wire from the inboard sensor goes directly to the fuel-gauge. Removing the wire from the sensor gives maximum full deflection on the gauge. connected to airframe = zero reading.

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23 hours ago, LANCECASPER said:

since I have already lost one fuel stick I would have been sad....    I just got another paint stirrer.   The first one was just a piece of red oak.  The harder woods have less wicking action

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