(Boat) Fuel Gauge Not Working - Diagnostics?

[Pancho]

I once had a boat which was wonderfully low tech. To tell how much fuel you had on board, you stuck a stick in the tank and noted which of my carefully crafted notches the level was up to.

Then I bought a new boat full of modern stuff and electricity. Most of it works most of the time - which is actually pretty good for anything on a boat. But the digital fuel gauge has now given up the ghost. It tells me the tank is 1% full - it lies like a cheap rug; it's the tank is damn near full.

So, any diagnostic tips? Bear in mind that somewhere in the measuring machinery, the stick has been replaced by electricity. Electricity and fuel (albeit diesel) scares the daylights out of me.

[Jaded]

So, any diagnostic tips

Stick a stick in the tank. 

[Mike J]

My father in law had a similar problem in that it always said empty when it was ful and he had to turn round the measuring thing.

[mrcharly-YHT]

I'd try the Yachting and Boating World - Sailing and motor boats for sale, forums, news | ybw forums - the practical boat one. Check the exact model of your guage.

Never had a boat with a fuel gauge myself.

[Panoramix]

First I would follow the wires and make sure that none of the contacts are corroded, apply some magical electrical spray everywhere.

Unicontact, Lubrification

If this is unsuccessful, I would try to clean the sensor, I think that some of them are screwed into the tank.

Ultimately I would make sure that my boat handling skills under sail are up to scratch as everybody know that marine engine have been designed to break down the day you actually need them.

Alternatively you could lend me your boat at the end of the season. If there is some bit related to the engine that could possibly go wrong, it will certainly go wrong. You can then call a good mechanic to take care of it during the winter and you will be assured of several years of trouble free sailing!

[Pancho]

So, any diagnostic tips

Stick a stick in the tank. 

Good plan.

Thought I'd try this - which prompted me to work out where the fuel tank was actually located. Eventually found it in the most inaccessible location possible.

[andygates]

It's going to be the sensor, wires, gauge or connections between 'em. 

Apply a battery of appropriate oomph across the gauge to see if the needle moves. 

Use a continuity tester (or multimeter set to resistance) to see if the wires are good.

Wiggle and jiggle and spray the joints.

Otherwise it's the sensor. 

[inc]

A lot of fuel tank senders are some sort of retained float, quite often a thin tube with an external ring which floats on the fuel surface and moves up and down with the fuel level. this changes the sensor loop resistance which is then converted into a gauge reading. A low reading with a full tank could mean a stuck float, it would be the first thing I would check.