Boat Fuel Gauge reads empty when boat is on and reads half when no key in

Question

Fuel gauge does work, no key get a reading, ignition on reads empty. I pulled the postive and negative from the sender and still got no reading, if i connect the positive and negative together will that give me a reading of a full tank (no resistance and bad sender) and if I still have no reading does that mean a wiring issue? Please help

Answer 1

Easy test sender wire center touch to ground wire if guage reads full guage & wire good> remove sender in tank connect again & test > If nothing or intermitent replace sended make sure the float is free to float as I have found  installed wrong and hit the side of tank>

Answer 2

You've answered the question, even if you don't know it.  No question it's a bad sender in the tank!  Now, fuel guages like this often don't work, and if they do they don't work accrately, not like` in cars.  In the old days, Chris Craft came with a wooden stick, which you used to dip in the tank...it worked.  Replace the sender, but don't expect much.  You don't have a wiring problem, proof is touching sender wire to ground, guage reads full....enough said!  Good luck, Oh and thank Jtexas, he's on target as usuial, even give him a best answer...

Answer 3

the sending unit in the tank is no good.   No gas is totally open connection (wires not touching)//mid full  some resistance)   Or, there is a gasket (or missing) between the sender and the tank.  Especially if the tank is made of metal this may be an issue of grounding.

Answer 4

Is this a new installation, or it used to work & now its broke, or it's a newly acquired boat?

Are you saying that key on, it points to E, or it drops to the bottom?  

And key off, it always points to half-full, or it reads the correct fuel level?  That one is kinda puzzling.

Key off, the needle should either float (stay where it was or bounce around), or drop to the bottom of the gauge (depending on the design of your gauge).  Shouldn't be getting any juice or else it's a parasitic drain on your battery.

If you take the sender wire off at the gauge, and use a jumper to connect the SND post to ground (key on).  It should go to empty, if it does, then the gauge is good and either the wiring or the sender is bad.

Check for corrosion/loose connections/chafed insulation.

Want to verify which it is, you can always use a jumper wire between sender & gauge.