Fuel Gauge Woes. Help needed please.

[iammarcuse]

I have a Key West DC2020 with a 140 Suzuki. It sat for a couple of months and the fuel gauge reads E yet I know it is 1/3 full. It seemed I was getting voltage back from the sender so I tried a brand new gauge. Still nothing. Swapping out the sending unit is a challenge as it is not right under the access hole and will require pulling out pedestal seats and the floor panel. So I want to make sure that is the problem first.

At the sending unit it reads 110 ohm across from sending wire to a known ground. That would seem right on 1/3 tank of fuel with a 230 -33 ohm sender. At the gauge I read 4.8V across the sending to ground. Which again seems about right given V12 at 110 resistance. But clearly I am missing something here.

Back at the gauge I read 4.8V from sending wire to a known ground. I also read 4.8V from the ground wire to a known ground. Does that sounds right? I am not 100% clear on how these circuits in a fuel gauge are supposed to work, so I don't know what to make of that.

I am wide open to solutions here. I must be missing something. Thank you.

 

[dingbat]

I have a Key West DC2020 with a 140 Suzuki. It sat for a couple of months and the fuel gauge reads E yet I know it is 1/3 full. It seemed I was getting voltage back from the sender so I tried a brand new gauge. Still nothing. Swapping out the sending unit is a challenge as it is not right under the access hole and will require pulling out pedestal seats and the floor panel. So I want to make sure that is the problem first.

At the sending unit it reads 110 ohm across from sending wire to a known ground. That would seem right on 1/3 tank of fuel with a 230 -33 ohm sender. At the gauge I read 4.8V across the sending to ground. Which again seems about right given V12 at 110 resistance. But clearly I am missing something here.

Back at the gauge I read 4.8V from sending wire to a known ground. I also read 4.8V from the ground wire to a known ground. Does that sounds right? I am not 100% clear on how these circuits in a fuel gauge are supposed to work, so I don't know what to make of that.

I am wide open to solutions here. I must be missing something. Thank you.

Fuel gauges don’t operate on 12V.

12 volts comes into the gauge and reduced to operating voltage (~5-8V) at the gauge to drive the meter.

The sender is connected to the ground side of the circuit.

You need to pull the sender to test operation.

 

[iammarcuse]

That is good information. Thank you. The one thing I have not checked is if I have a good ground at the sending unit. This is a salt water boat in Florida. I get bad grounds all the time. Especially underneath the floor where the tank is. If the ground is bad I would assume I would be getting nothing. Which is the case. I will check that first before I do anything else.

 

[Chris1956]

Sounds like a wiring problem. The sender does not ever get voltage applied to it. The sender changes resistance to ground, as the tank empties during use.

Check to make sure the power (+12VDC) and ground to the gauge are good. Check resistance from ground at the gauge to the sender wire at the gauge. It should be zero ohms.

 

[iammarcuse]

Solved. It was a poor ground to the sending unit. I could not trace where the ground went as it is under the floor. So I merely ran a new ground directly to the battery which was my easiest path. All working now. Thanks. Glad I didn't pull the sending unit.