C30 fuel sender failure

[dbsea]

I think my fuel sender is failing. Consistent inaccuracy and numbers bouncing all over the place. What one do I have (2016 C30) and where is it wired into? I assume somewhere on the engine given the fuel readout is on the EVC…

 

[Full_O_Fish]

The fuel tank sender is connected to the multi-harness which has inputs for fuel, freshwater, and rudder sensors. The cable connects back to the D6 on the port side connection block located by the heat exchanger. If replacing just the sender, disconnect the two existing wires and reconnect them to a new sender.

 

[BB marine]

The sensor is a KUS Reed Sensor. A relatively dependable sensor. If properly calibrated gives acute readings of fuel level. As stated in the previous post it is wired into the engine harness. If the gauge proves to be defective the only connection needed is at the sensor. You will see that connection close to the sensor at the tank. The fact that the Kus reed sensor is reliable I would not jump to the first conclusion that the sensor is defective. I would inspect all connections between the fuel tank sensor and the engine wire harness. The most probable would be the connection at the sender to the engine wire harness. Confirm a good tight corrosion free connection. If the wiring proves to be in good condition. The next troubleshoot would be to purchase a new sending unit. Before installing it in the tank connect the new sending unit to the fuel tank wires in the same configuration as the old sender was wired. Now test the sender with the EVC reading fuel level. move the float up slowly and confirm good steady increases in readings. Once you have moved the float to the top of the sender then repeat the movement to the bottom. Monitor the EVC readings for steady movement. If this proves to fix the issue I would recommend one more step before installing the sending unit in the tank. This is a step that Fluid Motion does not do during the rigging and commissioning of the boat. It is called (CALIBRATING THE FUEL SENDER ) Take advantage of the Volvo technology and properly calibrate the sending unit so it is accurate within 1 to 2 gallons of on board fuel. I did this when I owned my C26 and found the fuel gauge to be as accurate as the Garmin when the Garmin is perfectly calibrated after each fuel filling. I did find that over time the Garmin became less accurate because of the percent of error after each fill up. The Kus sending unit if properly calibrated is acute all the time with in 1 to 2 gallons. Below is a thread that I posted about calibrating the sensor for accuracy. This is the method that trained Volvo technicians use if they follow the training they received. I was shown this procedure by a tecj=hnician that worked at Volvo dealership that required all boats delivered will have an acute fuel gauge. That is what you would expect to receive when you purchase a Quality Boat!

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The link below shows the comparison of the Garmin and the EVC after I calibrated the sender. I also drained the tank until empty. Then filled the tank knowing the amount of full (gallons) in the tank. I ran the boat several days. After burning about 30 gallons of fuel I did the comparison Garmin reading to fuel gauge reading. The difference was .8 gallons. I believe the fuel sender to be the proper reading. The that point on I always used the Fuel sender reading when filling the tank. It was spot on!


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When ordering the sender you use the number on the top of the sender to get the right one. The number correlates to the fuel tank depth.

 

[dbsea]

Thanks both. In a moment of great annoyance last night I bought the maretron TLM100 and focus tube with the dead band eliminator. While Defender ships that, I’ll check the wiring harness to ensure a good connection and monitor it. If I do switch to the Maretron, I can’t fathom how I will get near 180 gallons of fuel out of the tank and then change the sensor and add back 1/16th of the tank capacity at a time to properly calibrate it. Probably best to wait till I’m close to empty…

 

[BB marine]

Personally I feel the Kus can be calibrated as accurately as the TLM100. The advantage of the Kus is it is 75% cheaper and can be calibrated without draining the tank. If you read my thread about calibrating the tank you will get a very accurate reading. When I calibrated my tank I emailed Fluid Motion Customer service and asked for a tank drawing of my 80 gallon tank.
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Using the dimensions provided in the drawings can be used to calculate fuel quantity at a specific fuel level. Once this is calculated the float is moved to a level where the resistance reading changes, mark this, measure the travel, compare it to the tank calculations. enter the amount of fuel at this level into the EVC. I have done this for the 80 gallon tank. If I was a Ranger technician rigging a boat for a customer for delivery. I would have all my calculations Done for that model and it would take me 10 minutes to calibrate a sender unit for accuracy. If I was a technician delivering Rangers and Cutwaters I would spend the time and do calculations for all models with different size tanks.( There are not that many!!) Record the calculations, purchase a sending unit that is used for each model (under $70 per sending unit and have these labeled and kept in my tool box for rigging and delivering a new boat to a customer. (That is a cheap tool! About equal to the price of a quality wrench!!)This is what a quality dealership would expect their technician to do and what a Quality boat manufacture would require. Many quality boat manufactures do this in the factory as part of the Quality Control steps confirming accuracy of a fuel gauge. A boat fuel gauge installed today should be as accurate as your automobile.

You will spend more time draining the tank and measuring the fuel going back in the tank then you would if you got a tank drawing and sat at your desk and figured out the gallons per volume. When I did my calculations I figure the volume for the irrgualt ship of the tank first. I drew a line across the tank. I then calculated how many gallons were in that section of the tank. Then I calculated the volume of the regular shape of the tank. Once I had theses amounts I could figure the amount of fuel at different levels based where the resistance changes are. If you look at the picture I posted you can see how I make the sender. This was all done with fuel in the tank and the new sender before installation into the tank.
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This is the first step,Have the new sender wired into the system but not in the tank.
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Select empty tank calibration, ( The factory uses full tank calibration. This is old school and not acute at all!) gallery2.php?g2_itemId=53501

Enter fuel tank capacity
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After this go thru the filling stages of the tank by moving the float up the sender shaft. Using the lines marks on the shaft where resistance changes are. Using your tank volume = gallons calibrations that you figured out from the tank dimension drawing enter the percentages of fuel/ gallons of fuel.

It sounds complicated but it is not. Once you think about it it is not hard. If an old dumb boat mechanic (me) can figure it out anyone can!

 

[dbsea]

Thanks Brian! I'll reach out to CW boats and see if they have a drawing of the tank...