Gauge or sending unit?

[redsonfly]

My 18 has a full tank of fuel, the gauge has power and ground, but it reads empty; the needle does not budge.
How can one determine if it's the gauge or the sending unit that is the culprit? The problem is that this is a later tracker boat and they did not spec the tank correctly and you cannot access the sending unit without removing the tank panel in the cockpit sole.
Thanks in advance!

[eggsuckindog]

I've put 2 sending units in mine in the last 2 yrs - I would just do a fuel flow meter - if you short the gauge it will go to full but I forget how to do it, thats the check for the gauge - usually the sender and based on what you've said meter it.

[Blue197320]

i would just put a new sender in it. ive had this one for a few years and no problems. sender

[JohnB]

If you ground the sender wire on the back of the gauge to the negative batttery, it should peg to full. Gauges rarely go, although mine went this year. The most common cause of this is a bad ground from the battery to the gas tank. I would check that first. If the gauge checks out, your going to have to get at the sender to check the wires. Check that you have resistance between the ground plate on the top of the sensor where the ground tab is, and the negative on the battery. Finally, check the sender wire, they can corrode and go bad too. Check both the wire and the connection. If you ground the sender wire off the tank, the gauge should peg full. All this needs to be done with the key on. Worst case, pull the sensor, and put a meter between the ground and the sensor wire, and when you move the float up and down, you should see the resistance change.

[uncleboo]

If you have to get to the sending unit, why not install an inspection plate, that is if you can determine where it is in relation to the tank cover. I thought my ground wire got severed while running some other wires and the guage quit working so I was prepared to install the insp. cover. Mine has an inspection cover near the front so I took a mirror, flashlight and tape measure to determine the center of the sending unit. (While under there, I found my ground wire and got mine working again. ) Good luck!

[redsonfly]

Uncle Boo, The wiring is ugly and a new home run snaked from the tank to the gauge is in order, for my sanity at least.
John B thank you for the electric test, it was exactly what I was looking for and will check out this evening.
Blue 197320 those sending units look terrific, alot better than the ones with the swing arm on them from the past. Thank you for the link.
Eggsuckindog the fuel flow system is indeed the best around, but I think it might be overkill on a little 18. Heck, my Hells Bay flats skiff came with a wooden stick as a gauge. I really prefer to keep it simple like that but I can't find a stick long enough for the 18!
Thank you all so much!
Redsonfly in Fort Lauderdale

[bobbert]

Yes those Wema senders are fantastic. Main thing is Ethanol does not effect the float. The Wema people are great to deal with. Use them on all my restore projects.
Also make sure you have 12 volts at the sender, Sometimes the ignition switch will not pass full voltage.