Wiring Fuel Sender Unit To Ignition

[Jason2tpa]

My recently purchased used boat needed a new electric fuel tank sending unit. This was replaced with no problems. However, I noticed the fuel gauge's ignition wire wasn't connected to anything (so to was the light bulb wiring). Just to be clear, there are two gauges on my console. One yamaha RPM/Oil/Temp gauge and the other gauge is a stand alone fuel gauge (no brand name).

The sender wire is properly attached to the "S" terminal. The sender ground wire is attached to the ground terminal on the unit, then a jumper wire from this terminal ground attaches to grounding panel on the console. So I'm confused as to where the sender unit's ignition wire is best to plug into the ignition's power wire. I looked at the back of the ignition's wire harness. I can't imagine splicing the sender unit's ignition wire into the console's ignition.

I've attached a photo of a similar fuel gauge. Take a look and let me know your thoughts. Many thanks!

[boscoe99]

In most Yams there is a small fused harness that runs from the key switch to the gauges. If you look at the gauge end of the harness there are typically three ports available for 12 volt positive power. That is where a Yamaha fuel gauge would normally be connected. If three ports are not enough then Yamaha makes a small harness that will connect to one of the three ports and provide even three more ports.

[Jason2tpa]

What a fantastic wiring diagram boscoe, thank you. I was only looking for such a port from the key ignition, not the tach gauge. Ok ill look for this. There be at least one open port because there are no other gauges on the console. Just so im clear, ill be looking for this open port coming out of the tach/temp gauge? And if indeed there an open port would it be plugged into like a dead end connector, or capped?

Also, while im under the console, i might as well connect the light bulb wire from the fuel gauge. This is a black wire just dangling. Where would this wire connect?

In most Yams there is a small fused harness that runs from the key switch to the gauges. If you look at the gauge end of the harness there are typically three ports available for 12 volt positive power. That is where a Yamaha fuel gauge would normally be connected. If three ports are not enough then Yamaha makes a small harness that will connect to one of the three ports and provide even three more ports.

[Jason2tpa]

Taking a look now. I see open ports for both yellow and blue. I plugged into Yellow but fuel gauge didnt move? Though i only turned key to power, not cranking. Rpm gauge came on but not fuel.

[boscoe99]

With the key on you should have 12 volts positive on the yellow wire. Black is ground. If the fuel gauge is provided with power and ground but does not work then it would seem the gauge is kaput. If the tach works but the fuel gauge does not work (connected to the same power and ground source) then that is further evidence that maybe the fuel meter is kaput.

Now keep in mind that the gauge can be operable but if the sender is not connected properly then the needle may not move.

Troubleshooting Teleflex Fuel Gauges

[rodbolt17]

and remember the tank sender must have a ground path.
if its a metal tank it must also have a bonding wire.
if the fuel fill is metal it must also be bonded to the tank and battery negative.

[Jason2tpa]

Used the troubleshooting guide. When connecting a short wire from sender term to ground term the gauge needle didn't move to full. Must be defected gauge. All other wires are in their correct place (including grounding tank and fuel filler).

With the key on you should have 12 volts positive on the yellow wire. Black is ground. If the fuel gauge is provided with power and ground but does not work then it would seem the gauge is kaput. If the tach works but the fuel gauge does not work (connected to the same power and ground source) then that is further evidence that maybe the fuel meter is kaput.

Now keep in mind that the gauge can be operable but if the sender is not connected properly then the needle may not move.

Troubleshooting Teleflex Fuel Gauges

[rodbolt17]

are you sure the sender ground and gauge grounds are good?

[Jason2tpa]

Havent tested resistance for each individual ground wire. That will be last test before buying new gauge.

are you sure the sender ground and gauge grounds are good?

[Jason2tpa]

Update-

The harness was bad. So i used a 3 way connector to splice off directly from ignition yellow power wire. Fuel gauge now works and gives an accurate fuel level compared to fuel in tank.

Thanks again for your assistance!