Fuel gauge / sender issues

[NYSail]

So have the traditional sailboat fuel sender with a float. Two wires attach to sender that lead back to the gauge. When I turn the boat on the dial goes immediately to Full....... its not full. When I take the wires off the sender it basically does not change..... wife said it actually moved higher. when I go to back of gauge, there is 12v and all looks to be connected fine. When I unplug the gauge falls to Empty. What could be causing this......... a short inside the gauge?

Thanks
Greg

 

[Davidasailor26]

A short inside the gauge does make sense. You could try unplugging the sensor and checking the resistance across it with a multimeter. That would help figure out if the sender is behaving correctly. You could also connect the back of the gauge to a resistor, maybe about 100 ohms, just to see what that reads. The other possibility is that the sensor is working correctly but the fuel level, even if it’s below full, just hasn’t dropped enough for the sensor to fall below full. It’s pretty common for the sensor response to be non-linear.

 

[Rich Stidger]

Here are two documents that will help you figure out the exact problem.

 

[sailcapt340]

I use this method, it comes from WEMA Gauges.

To test the sender simply:

• Disconnect the two wires on top of the sender.
• Remove the sender from the tank.
• Connect the wires on the sender to a multimeter.
• Set the multimeter to resistance [Ω ohms]
  
  
• Move the float to the top of the sender and take a reading on the multimeter:
  
  
• At the top of the sender (full) the resistance should be:
  • European specification - 190 ohms
  • American specification - 30 ohms
    
• Move the float to the bottom of the sender and take a second reading:
  
  • At the bottom of the sender (empty) the resistance should be:
    • European specification - 0 ohms
    • American specification - 240 ohms

If you don't get the expected resistance reading on the multimeter then the sender is at fault and will need replacing.

 

[dlochner]

And from MaineSail:

Testing A Marine Fuel Sender - Marine How To

Empty - Arm Down = 240 Ohms The fuel sender, for the typical US standard used in a marine application, is a simple device that presents a resistance reading to the gauge with which it is paired. For US fuel gauges, from the

marinehowto.com

The float on an articulating arm type senders do fail. The float gets saturated or crude builds up on the hinge which prevents the float from dropping. This problem is inherent in the design.

Kus (formerly WEMA) senders are top notch and are immune to this problem.

Sensing Quality, Gauging Success! | Home

World leader in technology solutions for marine, vehicle, & industrial applications. We design & manufacture level sensors, gauges, DEF tanks, & accessories

kus-usa.com

 

[JoeWhite]

Here is the one I use.

 

[JamesG161]

What could be causing this......... a short inside the gauge?

See the image above by @JoeWhite. The black thing is the float.

Older Wema floats cracked and became Diesel fuel soaked.
Their new one is encapsulated and will not crack.

I had to change mine, works great now. Their model number is stamped on the Sensor Box as shown in the same picture.
You will need to see your Stamped marker to have Wema USA now [ KUS USA ] send you a replacement [ length etc marked on it]

Mine works great now.

Jim...

PS: You can talk with them and learn how to just unscrew the old sender unit. The new Unit just screws back in the wires should match up.

 

[sailcapt340]

This is what can happen. It did to me. This is my Fresh Water Sensor.
And like Jim said…the older ones (like mine) can crack, can absorb and will over time. I believe, at least for mine, it was chlorine absorbed over time.
The new ones are made under better standards and controls by WEMA, not farmed out to secondary manufacturers.

 

[Benny17441]

Mine is broken and that is one thing I have not taken the time to fix. I do not need an instrument that at best can only tell me if I have a lot of fuel or very little. I have been following for years the average burn rate calculations that will yield at any moment the amount of usable fuel left in the tank. All it requires is an Hour Meter, a refueling log pad and a few calculations. Besides providing a much more accurate fuel situation the hour meter can be used to schedule maintenance and the results can be used to calculate fuel range based on conditions on the water. There is plenty of info on the Archives.