# fuel gauge or sending unit?



## Little Jimmy Cook (Oct 22, 2004)

I searched the threads but I could not find what I was looking for.





I am trying to fix my recently replaced fuel gauge. I replaced the stock faded and non working fuel gauge with a Teleflex fuel gauge. I was able to track down a black ground wire to the sending unit that had been knocked off and reattached it to the sending unit and the new gauge showed a full tank of gas. I thought I was good to go, because I had just filled the tank up. I ran the boat last week and should have been at least at ¾ full or half full, but the gauge still shows a full tank of gas. Should I be looking for another wiring issue or do I need to replace the sending unit now as well. I hate to make a stupid embarrassing mistake on the water such as running out of gas. I cannot visualize the tank because it is below deck and aluminum. I would like to make this an easy fix and get back out on the water soon. I could take it to my boat shop, but I can probably do this myself and save a few weeks of time since it is their busy season. 





I would love to go out again this week and put a little more distance this time, but would like to make sure the gauge is good to go. Please post any messages on what I should look for so I can go to work.



My e-mail is [email protected] or pm me.



I appreciate your time and effort.


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## stargazer (May 24, 2004)

Only the positive accessory (Purple wire) wire from the engine harness is connected to the IGN or I Terminal on the gauge.
The negative or ground terminal of the gauge is connected to the boats grounding system.
The S or Sender terminal is connected to the Fuel tank sender.
The fuel tank must also have a connection to the boats grounding system
To troubleshoot your boats fuel gauge and sender, Do the following. 

After insuring that your wiring between the fuel sender on the tank and the connections on the fuel gauge are correct.
Turn the Ign Key to "ON" and Using a jumper wire, ground the center or S terminal on the fuel sender at the tank
If your fuel gauge jumps to the FULL reading, the problem is in the fuel tank sender.
If your fuel gauge does not move, proceed to the next step.
Using a test light, with the key in the on position.
Check for power at the I or Ignition terminal on the gauge.
If Power is "ON" at gauge terminal, ground "S" terminal and "G" terminal and check gauge reading. If reading moves to full then you have a wiring problem between gauge and sender,otherwise gauge is defective.
If the power is "OFF" at the gauge terminal, check for ground by connecting tester to Ignition switch "RED" terminal and to the "G" Terminal on the gauge. If the ground is good, use a jumper to power gauge "I" terminal and retest gauge.
Once problem has been diagnosed properly, repair as required.
To replace fuel sender, clean area thoroughly and remove the six screws around the sender that secure it to the tank
Remove the sender and set aside
Measure the tank depth for proper sender recognition. There are two lenghts of senders generally used and you must purchase the correct one.
Follow the instructions provided with the sender when setting the depth.
After sender installation is complete, check ground wire on the tank that attaches to the boats battery negative terminal or to the boats grounding system.
If wiring needs to be replaced. Use the standard wiring color codes as follows:
Fuel Sender "S" terminal wire is "Pink"
All grounds are "Black" wire.
The "I" Terminal wire, between gauge and key switch is "Purple".
When ever possible use "Tinned Primary" wire of 14ga for fuel system wiring.
 *Standard Marine Wire Code Table*​*Red*Constant Hot*Black*Ground*Purple*Key-on Power*Yellow/Red*Neutral Safety*Tan*Water Temperature*Dark Blue*Gauge Lighting*Pink*Fuel Sender*Gray*Tachometer*Light Blue*Oil Pressure*Brown/White*Trim Indicator*Brown*Bilge Pump*Green/White*Trim Down*Blue/White*Trim Up*Green/Orange*Independent Tilt Down*Blue/Orange*Independent Tilt Up*Yellow/Black*Choke Circuit*Yellow/Red*Starting Circuit*Black/Yellow*Ignition


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## High Plains Drifter (Jul 16, 2006)

Sounds like a stuck sending unit. They tell me the sending units hardly ever fail though. The problems i've found on mine are the connections on the sending units must be crystal clean and very tight. One bit of oxidation throws the thing into turmoil.

Grande


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## CaptPb (Jan 26, 2005)

They do fail and I've never seen one that was pinpoint accurate either. All a fuel gauge is, is a small volt meter that measures the resistance provided by the sending unit. It recieves a specific amount of DC voltage. As the float arm move up or down it raises or lowers the amount of resistance (voltage returned) to the gauge.The above procedure will work but the quickest way is to use a real multi-meter and not a test light. Actually measure the amount of votage supplied to the sending unit and the resistance it returns to the gauge. You will need to know brand and resistance values for the sending unit to varify. If there is zero current comming back from the sending unit, it's fried. Also Teleflex gauges don't realy like other brands of sending units because they opperate with different resistance values. That could be the culprit from the start.


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## Little Jimmy Cook (Oct 22, 2004)

*Gauge is looking to be the problem*



stargazer said:


> Only the positive accessory (Purple wire) wire from the engine harness is connected to the IGN or I Terminal on the gauge.
> The negative or ground terminal of the gauge is connected to the boats grounding system.
> The S or Sender terminal is connected to the Fuel tank sender.
> The fuel tank must also have a connection to the boats grounding system
> ...





If Power is "ON" at gauge terminal, ground "S" terminal and "G" terminal and check gauge reading. If reading moves to full then you have a wiring problem between gauge and sender,otherwise gauge is defective. 
I have power at the I and grounded the S and the G and got nothing on the gauge. I guess this means I bought a brand new defective gauge? I guess I will buy a Evinrude gauge and start over.

Thanks for the input this one has had me stumped. After I replace the gauge again I will post up so everyone knows the outcome.


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## stargazer (May 24, 2004)

Now hold on a bit be fore you go buy a new gauge. Was it tested on the boat? Try this, do the test straight off the battery itself. Jump from the pos side of the battery to I, Then ground both the S and G to the neg side of the battery. this will take all the guessing out of if the gauge is working.
I am sure you can get a bad gauge new but, its very uncommon. 
Let us know what ya find.
In all honesty.....if you can afford it. Ditch the whole shooting match and get with JTBURF (sp?) he had a Navman F2100 DIG fuel gauge for about 120.00 bucks. no guessing on the fuel, know exacitly what you have.


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## fishsmart (Dec 5, 2004)

It is usually the wiring, then the sending unit. Check here for a better sending unit:

http://www.centroidproducts.com/tableofc.htm
http://shopping.rexmar.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=CENCGF-12&Category_Code=AMmarSender

Charles


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## Little Jimmy Cook (Oct 22, 2004)

*Sending unit*

It was the sending unit.

Thanks for all of your help. I have the gauges installed and working and ready to go fish.


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## stargazer (May 24, 2004)

Great,,,glad you got it working.


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