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  Fuel Gauge Stops Working

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Author Topic:   Fuel Gauge Stops Working
Caribe posted 06-01-2011 09:21 PM ET (US)   Profile for Caribe   Send Email to Caribe  
[The] fuel [gauge on a 2002 Boston Whaler DAUNTLESS 16] worked last week and is now not working. It shows FULL. I'm nervous as I just got the boat, and I have no feel for fuel tank level or fuel usage. Give me advice, starting with letting me know where it [?] is located? Thanks so much. Ian
jimh posted 06-01-2011 09:26 PM ET (US)     Profile for jimh  Send Email to jimh     
You will have to tell readers where the fuel gauge is located. We will need this information to help understand what sort of fuel gauge you have. Do you have an electrically operated remote fuel gauge?
jimh posted 06-01-2011 09:37 PM ET (US)     Profile for jimh  Send Email to jimh     
Assuming your fuel tank level gauge is a remote electrically operated gauge, there is typically a variable resistance sender unit on the fuel tank. Most often these sender units are mechanically coupled to a float mechanism via an arm or lever. The float moves with fuel tank level. The arm is mechanically coupled to a rheostat.

Electrical current from the battery positive (often via the ACC circuit of the ignition key switch) flows though a current limiting resistor, through the meter movement of the fuel tank level remote gauge, and then to the rheostat on the tank. The return current from the tank often is isolated and flows on a separate conductor back to the meter, but it can also (if a metal tank is used) be connected to the tank itself, which is in turn connected to the battery negative. The current flow in the circuit becomes proportional to fuel tank level.

The circuit is quite simple for anyone familiar with DC electricity. An investigator with such familiarity should be able to diagnose problems with the circuit with ease.

The fuel tank level sender is typically located somewhere in the middle to aft portion of the tank. On Boston Whaler boats it is typical that a removable deck plate is located in a position to permit access to the fuel tank level sender when the deck plate is removed.

Caribe posted 06-01-2011 09:45 PM ET (US)     Profile for Caribe  Send Email to Caribe     
The fuel [tank level gauge] is in the center console. I really can't figure out where the sender is. My boat has the 45-gallon tank. Thanks, so much for your help.
jimh posted 06-01-2011 10:16 PM ET (US)     Profile for jimh  Send Email to jimh     
quote:
"I really can't figure out where the sender is."

I described the location of the sender in my article just above.

Caribe posted 06-01-2011 10:24 PM ET (US)     Profile for Caribe  Send Email to Caribe     
Ok, thanks. I'll check it out in the daylight. Is this something that is easy to remove or do you need to take off the pilot seat? Thanks again.
jimh posted 06-02-2011 09:37 AM ET (US)     Profile for jimh  Send Email to jimh     
You have observed that the remote fuel tank level electrical gauge shows FULL. Does the indicator on the gauge move to the FULL position from the resting position when power is applied? Or does the gauge rest on the FULL position when no power is applied?
Caribe posted 06-05-2011 09:42 PM ET (US)     Profile for Caribe  Send Email to Caribe     
Thanks for all your help. It only shows full with power on. It is at Empty with no power applied. It is frustrating as I have no idea how much I have in the tank. The fuel tank keeps burping also when I add fuel, so I'm not sure if it has ever been full.
jimh posted 06-05-2011 10:11 PM ET (US)     Profile for jimh  Send Email to jimh     
Since the gauge indicator moves when power is applied, it is reasonable to assume that current is flowing through the entire circuit. The FULL position usually means more current is flowing which corresponds to less resistance from the fuel tank level sender. This could be an indicator of

--the float level is stuck and falsely signaling the tank level; or,

--there is a short circuit around the rheostat in the fuel tank level sender, and the current from the gauge is just being shunted to ground.

I would next try to measure the resistance of the fuel tank level sender rheostat, and also inspect the area to make sure there are no short circuits.

Caribe posted 06-05-2011 10:19 PM ET (US)     Profile for Caribe  Send Email to Caribe     
Ok, I'll do that. My only concern is that I can't find where the fuel sender is. I'll check the diagrams on the whaler parts website. Thanks again.
Caribe posted 06-09-2011 10:03 PM ET (US)     Profile for Caribe  Send Email to Caribe     
I found the fuel sender. Under the pilot seat. I'm going to work on it in a week or so. Thanks!
davej14 posted 06-10-2011 09:45 AM ET (US)     Profile for davej14  Send Email to davej14     
Be careful with electrical around the fuel tank when you remove the sender.

You should be able to see the fuel tank from one of the aft inspection covers. The tank is translucent so if you shine a flashlight beam against the tank you will be able to visually confirm the fuel level.

Another useful option is to install a fuel flow sensor in the fuel line that will monitor the usage and calculate the fuel remaining, distance to empty, etc. I use a Lowrance sensor that displays this information on my combo GPS/Depthsounder. After calibration is is very accurate, much mo so than the fuel gauge on the helm.

davej14 posted 06-10-2011 09:50 AM ET (US)     Profile for davej14  Send Email to davej14     
http://www.nasa.gov/mission_pages/shuttle/main/index.html
davej14 posted 06-10-2011 09:53 AM ET (US)     Profile for davej14  Send Email to davej14     
Sorry about that last link, I just bought tickets for the last Shuttle Launch and didn't clear my clipboard. I meant to post the following link to the Lowrance fuel flow sensor. It is a very easy mechanical connection and electrical hookup to an existing Lowrance display. I'm sure other manufacturers offer a similar option.

http://www.lowrance.com/Products/Marine/ LowranceNET-Marine-Networking-System/Product-Guide/ Electronic-Probes-EPs/EP-60R-Fuel-Flow/

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