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my fuel gauge has stopped working

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WileyOne

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The gas gauge in my 2001 Sea Ray 190BR has never worked right as long as I've owned the boat. It has always read lower than it should, never quite reaching the Full mark. I'm pretty sure the tank is full because I can't squeeze any more gas into it.

Recently, the gauge stopped working completely.
Now it hangs just above empty, regardless of how much fuel is in the tank.

I probably need a new gauge or possibly a new sending unit.
How can I determine the problem using a multimeter?
Can I buy only a gauge or just a sending unit?
Are they pretty standard? Will different brands generally work with each other?
How much trouble to install a sending unit inside the plastic fuel tank?

I'm a pretty good electronics tech and a pretty good mechanic, but not real confident digging into a fuel tank.
 
Not sure on your particular boat. However, 9 times out of 10 it will be your sending unit in the tank.

There should be an access hatch on your deck. Typically, it's a 6" round pop-out hatch. Open it up. The sending unit will be right under the hatch. The sending unit is typically secured on the top of the tank with 6 small bolts. Disconnect the connectors, unscrew the bolts and gently remove the sending unit. Try to save the gasket. If it is a metal arm on a float, note the amount of throw from the highest point to the lowest point so that you can set up the replacement properly. Some sending units will not have an arm, but rather a float that moves up and down inside a sleeve. The principal is the same.

You can test the sending unit by hooking up an ohm meter to the lead, or leads. If only one lead, the base place will be the ground. As the arm is moved up and down, you should see the resistance change proportionally. If you don't see that the sender is bad. Make sure that the float is not damaged or soaked. Sometimes they just stick in one position due to corrosion.

Replacements are all over the Internet. The last time I replaced mine I noted that West Marine typically carries most types of replacements.
 
you can test the gauge by removing the wire from the sending unit. apply power to the gauge and take a 240 ohm resistor and connect it between the S terminal on the gauge and GND...gauge should show E. do the same thing with a 33 ohm resistor and it should show F.

If that's good, I'd suggest repeating the tests with the resistors at the sending unit. In other words, if the gauge proves usable, make sure the wiring from the gauge to the tank is sound...if that works, the sending unit is all that's left.

FWIW, fuel gauges on boats are notoriously inaccurate...my experience is if you need to calibrate the sending unit, worry about the E side more then the F end...
 
There are several videos on U-Tube that address trouble shooting and replacement of the proper component. They are quite detailed with good explanations.
 
I had issues with my fuel gauge as well. the indicator fluctuated according to waves, difficult to read and sometimes stucking.
I was obliged to run always with full tank.
I tested the sender with a multimeter while loading slowly 40 liters of gasoline; I realized that the level sensor was broken and impossible to replace,.

...therefore I decided to build my own gauge with a multifunction display...
since there is a microcotroller inside, I've implemented a fuel optimization in the sw.

motor_repair2.png


 
Fuel tank senders with any kind of float are notoriously inaccurate- if this isn't the OEM sender, I would bet that whomever installed it didn't bother to set it accurately. That said, how would someone do that if they aren't sure the previous one was cut to the correct length and bent properly. That takes a lot of trial & error, so it may be best to check the sender's ability to be set more accurately and if the gauge doesn't show full when it's full and empty when the float is wherever you decide to set it for 'empty', replacing the gauge isn't a terribly expensive step.

All things considered, I would worry more about having enough fuel to return to dock than not having a full tank, so a happy medium is needed. I would rather operate between 1/4 full and slightly more than 3/4 full with the gauge reading Full than to think I need to go incredibly far, but on large bodies of water, range is definitely important.

Sender resistance isn't standard to a high degree of accurate across the board, but the info posted previously about 33-240 Ohms is as close as you're likely to find.

I have an '84 4Winns and the gauge reads low, even though I have a new sender and the needle deflects fully when I touch the pink wire to ground. I don't hold it on the grounded part, I just touch it briefly. I'll work on its accuracy before I take it out this year- last year, I just wanted to do the virgin cruise after repairing all of the damage caused by the previous owner. The good news- I couldn't have asked it to run better.
 
Hello Jim, I'm fully with you that sender must be properly installed and gauge calibrated for that. It's very common to see gauge indicating half tank while in reality is full. That's annoying even if on the conservative side.
Anyway the latest gauges have a microprocessor inside that can be properly instructed on the shape of the tank, lower and higher values, and most important, damp fluctuations to read clearly the average.
 
Efisio said:
Hello Jim, I'm fully with you that sender must be properly installed and gauge calibrated for that. It's very common to see gauge indicating half tank while in reality is full. That's annoying even if on the conservative side.
Anyway the latest gauges have a microprocessor inside that can be properly instructed on the shape of the tank, lower and higher values, and most important, damp fluctuations to read clearly the average.
Click to expand...
Are you referring to the type with the tube and float with magnets or the capacitive senders without a pivoting float (many were from Moeller)? I have serviced those in boats since the late-'90s and they're good, but MTBE and Ethanol cause the magnets to fall out and the capacitive ones are very sensitive to fuel that has become contaminated- if it was set up with clean fuel, using fuel with additives causes the accuracy to go out the window. Damping the needle's movement is definitely a good thing, though.
 
jimn said:
Are you referring to the type with the tube and float with magnets or the capacitive senders without a pivoting float (many were from Moeller)? I have serviced those in boats since the late-'90s and they're good, but MTBE and Ethanol cause the magnets to fall out and the capacitive ones are very sensitive to fuel that has become contaminated- if it was set up with clean fuel, using fuel with additives causes the accuracy to go out the window. Damping the needle's movement is definitely a good thing, thou
Click to expand...
Do you have experience with ultrasonic senders?
They measure the change in transit time of sound, caused by the rising or lowering of the gasoline.
 
You are right again, radar or ultrasonic technology is more common on big boats, yachts, cruise vessels, cargos ect. because of the dimension of tanks and budget available... but this no more true and I can't say more to avoid to be banned 😁
 
Efisio said:
You are right again, radar or ultrasonic technology is more common on big boats, yachts, cruise vessels, cargos ect. because of the dimension of tanks and budget available... but this no more true and I can't say more to avoid to be banned 😁
Click to expand...
The large ships are really, really hard to stop when they run out of fuel so it's most critical but the puddle-jumpers under 50' get the cheap parts. They're also serviced by people who aren't at the technical level of the bug guys and boat dealers are notoriously unwilling to train people well, as well as paying what they're worth. The industry is losing people, schools aren't teaching subjects that are needed by people in many technical fields and boat owners are stuck with whatever they can find WRT service.

I hope I didn't post anything that might cause me to be banned, but it's all true.
 
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