Stuck Fuel Guage

[dave6330]

Problem: The guage for my diesel tank seems to be stuck on full. When powered off, the guage drops to 'empty' but when turned on, pegs out on 'full' even though I know there's less than a full tank. I've found what I believe to be the guage on the top of the tank (a plate screwed on with calking around it and wire leads). I know it sounds like I'm a simpleton, but does introducing air into the fuel tank cause any problems? I wouldn't think so but the last thing I want to do is break something with my tinkering.

Question: What landmines are involved if I simply remove the calking, unscrew the plate and pull the guage to see if it can be unstuck?

[artbyjody]

Its not a "pressurized system", so remove the sensor sending unit from the tank as you like. Sometimes those floats will get crud on them and stick like that.

[Quickstep192]

As an added safety measure, I'd be certain to make sure all power is off and remove the sender wire before taking it out.

[Rockter]

You will not lose much by looking at it, and it is probably easy to re-seal it.
In the tank, you have what's known as the "sender"... a form of transducer. The guage (presumably elsewhere) , gives you the reading. The guage is really a current measuring device. Probably the sender float is just stuck in the up position. If a wire was broken, or had fallen off, I would expect it to read nothing all the time.
I don't think the sender float has flooded, otherwise it would read empty all the time.
It's worth a look to open it.
It is very easy to test them... you just push the float up and down and watch the readings.
Beware if the tank is a gasoline tank. Gasoline is very unforgiving. All your testing wil have to be remote, with the float taken out completely and no power delivered to it until it is.
Is it a diesel tank?

[dave6330]

Thanks guys. As I said, it's a diesel so I don't think I risk explosion or anything. I WILL cut the current when I check it out until I have the sender out. If I have to replace the unit, are they hard to match up with the OEM product? The boat was made in sweden and I might have some trouble tracking down an exact match.

[Idiens]

Let us know what you find. I have the same symptom on one of my gauges but I am suspecting a short circuit somewhere rather than a mechanical fault.

Trouble is, I can't remove the sensor from the tank without removing the tank and to do that, I have to remove the engine.

[SteveInMD]

I just went through this over the summer. I replaced the sender. Normally you do not need to go back the boat manufacturer to find a replacement.

Sometimes you can run into problems getting the tank to seal when you put it back together. The key clean off the old sealant, then use something like Permatex RTV sealant when you put it back together. Do not over tighten the screws when you reinstall. You don't want to squeeze all of the sealant out for this type of seal. You wont know if you have a good seal until you either fill the tank to the top so you have diesel sitting in the filler hose, or you go sailing and heel the boat over with a nearly full tank. Keep a close eye on it until you are sure it is sealed properly.

[ianhlnd]

The best fuel guage is a stick. If it breaks, get a new stick.

[billangiep]

I'm with ianhlnd on this one..I call mine a story pole, I used a dowel and put markings and notches at every five gallon point then varnished over it. Another idea if you can' insert a dowel is to string some wooden beads together with a colored bead at each 5 gal. point?

[SteveInMD]

Also you could replace the electric gauge with a mechanical one. The gauge sits right on top of the access port. They are much much more reliable then the electric ones. The reliability far outweighs the slightly less convenient placement for reading the fuel level.