Fuel Gauge Function

On my 30+ the fuel gauge started only working if it was over half full. Then it stopped working all together. I naively hoped it was just a gauge problem since West Marine had them on sale for $20. No such luck. When the power is applied to the gauge it actually dips a bit more negative.

I have looked for broken or loose wires but don't see anything wrong.

Can anyone tell me how to diagnose the sender. I can get at it if I have to.

Will a volt ohm meter tell me what I need to know if I have the sender out of the tank?

Thanks for any tips or advice.

Vern Kleist
Via Mar
Ericson 30+

I do not know the exact values but an ohmmeter connected across ground and the wire connection(blade connection) of the sending unit should show a gradual change as the float moves. Maybe your float is no longer floating(quite common)

Sounds like a stuck float. To test the sender you'll need to remove it from the tank so you can actuate the float mechanism. The range should be 240 to 30 Ohms. (Probably not exactly, but close.) With a multimeter set to the resistance setting (Ohms) you can connect the probes to both wires. When you move the float the reading should change from 240 at one end of the float range to 30 at the other end. (Not sure which is "full" and which is "empty.")

Nigel Calders book on Deisel Engines has a section on testing the temperature gauge. Don't recall if he covers fuel gauges.

I checked my temp gauge using his method and also by replacing the sender in the circuit with a variable resistor (potentiometer - which is all the temp sender and fuel sender are) that operates in the same range to find out what the resistance reading was at the operating temperature. You could do the same thing with the fuel gauge; as you change the setting on the potentiometer the gauge reading should change as well.

WEMA sells sensors and gauges. A new sensor is only around $40. Plus they are having a 30% Off Summer Sale right now...

http://www.wemausa.com/tank_sensors/tank_level_sensors.htm#Fuel_Water_Tank_Sensors