Sending unit question / Help

[Papa J]

1998 Grady 272 Sailfish, twin OX66. (new to me purchase)

2 Fuel tanks.

On the digital Yamaha gauge the fuel level just flashes at the lowest level. (bottom bar).

On the helm there is a rocker switch that has option for main and aux tank.

I know the aux is full or near full but still nothing on the gauge.

Starting with pulling the sending units to make sure they are actually working and applying a good ground since from what I remember sending units work on ground, is there anything else I can start checking.

I'm not an expert but know just enough to get in trouble. So any other advise would be appreciated.

I do have a power probe to be able to bring a good ground if needed.
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[fellinger]

I have the same problem which I need to address before the season. Make sure the terminals are clean and the plugs are corrosion free. I is most likely the problem. In the absence of a meter you could disconnect wires from the main sending unit and apply them to the aux tank sending unit and check to see if it is the actual sending unit.

 

[ROBERTH]

I had to replace both of mine within a year after I got the boat. Not hard to do and not that expensive. Most of us are getting them from WEMA and they are quality units.

Just measure the depth of the tank and you can order from them. I think you subtract an inch from the total depth, but there was some info on their site about it.

 

[seasick]

If you can get to the sender wire at the tank, unplug it and connect it to a known good ground using a piece of wire. The display should read FULL. you may want to flip the tank select switch to the other position to make sure you have selected the correct tank and sender wire.
If you can't get a full reading, you need to work backwards towards the display itself and ground wires to see if the display works. Getting to the actual sender wire at the display may be a challenge if there is a wiring harness. You can also try grounding the common terminal of the tank select switch to see if the gauge reads full.
The sender may be bad or the tank ground is bad.
if you determine that you need a new sender keep in mind that if the tank is full or nearly full, opening the sender flange can results in fuel spillage.