FUEL GAUGE PEGS FULL INTERMITTENTLY ?

[DCarlton]

Hello again.  I'm in the middle of an annual on my '67F.  The left fuel gauge pegs full against the stop intermittently.  Sometimes it works normally; sometimes it doesn't.  It's pegged now while sitting on the jacks in the hangar so I have an opportunity to chase the problem.  The tank is half full.  When I shut off the master, the left gauge doesn't drop back to empty unless you tap on the meter.  The right gauge slowly drops back to about empty on its own.  It feels like I may have more than one problem.  First I'm wondering if there may be a bad wire or ground wire on the outboard sender since it's pegging but sometimes working?  Or is it more likely the outboard sender?  I could also send in the gauge assembly for service and calibration but I don't want to just search for the problem randomly.  Has anyone experienced this type of failure?  Any idea on root cause?  Appreciate your time.  Thanks.  

[carusoam]

DC,

Good news! Everyone has experienced these challenges… 

Better news…

The whole system can be OH’d…. 
 

The floats are pretty easy to find, remove, clean, and put back…

Gauges can be calibrated, or OH’d…

 

Best news… that original system wasn’t very good on its first day…

If going with a modern engine monitor….  Add Ceis fuel floats to the system…

 

Check to see how much fuel you are really carrying… the original M20C had one float per tank for 26 gal per side…  larger tanks may have gotten a second float wired in series…

PP thoughts only, not a mechanic…

Best regards,

-a-

[apriav]

It's an open or ground.

Remove the wire from the sender and see what happens.

If it dose not change you have an open sender. If it goes the other way then it's a short.

Most likely a wiper, resister coil problem in the sender.

Cleaning the wiper, adjusting wiper tension, or coils cleaning may help.

Ceis replacement is the fix.

 

[DCarlton]

37 minutes ago, apriav said:

It's an open or ground.

Remove the wire from the sender and see what happens.

If it dose not change you have an open sender. If it goes the other way then it's a short.

Most likely a wiper, resister coil problem in the sender.

Cleaning the wiper, adjusting wiper tension, or coils cleaning may help.

Ceis replacement is the fix.

 

Thanks.  Seems like I remember the wires to the outboard fuel sender being accessible from the inspection plates on the bottom of the wing.  It's been a while though. 

[Yetti]

I vote short

[luv737s]

Had this same problem.  The ground wire behind the gage was loose.  I could reach up behind the gage and push the wire and the gage was reading correctly.  Thought it was the senders, had both overhauled (needed it anyway) but that was not it.  Really check that wiring.  

 

Mike