fuel gauge issues

rpatton

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Feb 17, 2011
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Not sure I'm posting to the right section but, I have a new to me pontoon this year and the fuel gauge does not work. I'm not new to boat but my electrical trouble shooting stinks. Can someone explain to me where to start. Not sure if its the guage, sending unit or somewhere in between. The toon is a Lowe 2001. Thanks
 

Teamster

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Nov 8, 2010
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On my boat last summer I chased a fuel gauge issue until it drove me nuts,....I never did figure out why it quit,...,

This spring when I dropped it off at my mechanic for an engine tuneup I asked him if he had the time to look into it,...

When I picked it up he showed me where the on/off switch was for the fuel gauge,.....And it switches between the two tanks,...

Otherwise check and see if the float is stuck in the tank,...
 

wrench 3

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Aug 12, 2012
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2,108
Assuming that the gauge isn't working at all. Get an old style 12V test light. Hook the ground clip to the plate on the sender or the ground terminal. Touch the probe to the sender terminal. With the ignition on the gauge should move.
If it does, the sender is the problem.
If it doesn't, do the same thing at the gauge. If the gauge moves the problem is in the wiring to the tank.
If it still doesn't move, check for power and ground at the gauge. If they are OK the gauge is bad. If they're not fix them.
 

rpatton

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Feb 17, 2011
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Thanks wrench, do I use a test light or I read somewhere torun a jumper wire from the ground to the terminal. Wouldn't they short out
 

Bondo

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Thanks wrench, do I use a test light or I read somewhere torun a jumper wire from the ground to the terminal. Wouldn't they short out

Ayuh,... The gauge measures resistance to ground,.... The sender varies resistance to ground,....
 

wrench 3

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Thanks wrench, do I use a test light or I read somewhere torun a jumper wire from the ground to the terminal. Wouldn't they short out

A wire to ground will peg the gauge to full scale. Still lets you know if it can work. A test light will give you a partially full reading. The test light is safer if you have to test at the gauge (in case you touch the wrong terminal). Also it can be used to check for power and ground.
 

rpatton

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OK , finally got time to look at the boat. I jumped a wire from the center post to the ground wire on the sending unit with the key in the on position. The guage did not even twitch. So step 2 is , I took a multi meter and checked voltage at the unit and it only showed about 2.3 volts. Is that a normal reading, or am I doing it wrong. Where do I go from here. I would really like to get this thing working.
 

wrench 3

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Was the 2.3V at the positive terminal of the gauge or the sender terminal of the gauge? If it was the sender terminal, that's in the ball park.
If you have good voltage to the gauge and a good ground, ground the sender terminal and see what happens. But make sure that it's the sender terminal that your grounding.
Is the ground wire to the tank OK?
 

rpatton

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Wrench, that reading was from the top of the tank on the sending unit. I also checked the voltage at the gauge and it reads a full 12 volts. I figured the ground at the sender was good because I got some voltage and my tank is plastic , so something is grounded
 

garbageguy

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May 8, 2012
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I cleaned up my fuel gauge's wire ends and connections at the sender unit at the tank, then coated with dielectric grease. Easy to do and helped immensely. It seems ground connections are often the culprit in electrical problems.
 

wrench 3

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Wrench, that reading was from the top of the tank on the sending unit. I also checked the voltage at the gauge and it reads a full 12 volts. I figured the ground at the sender was good because I got some voltage and my tank is plastic , so something is grounded

I'm afraid that I need more clarification. Was that 12V at the gauge on the supply from the ignition switch or on the wire to the tank. If it was at the line to the tank, connect your test meter to a known good ground (battery negative, engine block, ground circuit at the gauges) and retest the voltage at the sender unit. If you get 12V, the ground to the tank is bad. If you still get a low reading, the wire from the gauge to the tank is bad.
 

rpatton

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Feb 17, 2011
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Thanks , and bare with me here. I'm a decent mechanic but electrical I'm not so good. the 12 volt was on the ignition supply side of the gauge.
 

NYBo

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No Title

Google is your friend:
 

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wrench 3

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Nice diagram Bob. I can never find a loadable version when I need one.

rpatton: If you haven't acquired a test light yet, ground the S terminal on the gauge. Be very careful! With the key on the gauge should move. If it doesn't, you have a bad gauge. If it does, go back to the tank but this time ground it from a "known good ground". If the gauge moves this time, the tank ground is bad. If it doesn't, the wire from the gauge to the tank is bad.
 

Silvertip

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Hmmmm -- nice that "MY" diagrams are ending up all over the web!!!!!!!
 

gm280

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Jun 26, 2011
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Understanding that everybody doesn't understand a typical fuel sensor to gauge setup, or even explanations of how electronics works, pictures are very informative to accomplish that. Without getting into such electronic lingo, if you have good shiny clean connections and proper gauge setup and no reading, look to the tank's sensor. But if you do buy a new fuel tank sensor, make sure it is the one for your gauge type. There are two different types (resistive readings) available and you will need to know why type your gauge uses. JMHO!
 

rpatton

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Feb 17, 2011
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Thanks gm . now how do I tell the difference between the two
 
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