Re-Calibrating Command Link Plus

[Jonah272]

Hi all,

While tinkering in the settings of my Command Link Plus, I decided to see if the previous owner had properly entered the tank sizes. In doing so, I inadvertently reset the calibration of the sending unit for my main tank. It was previously reading at 25%, and now reads 0%. (In my defense, Yamaha made it very easy to do that—no warning signs popped up or anything.)

I've read the manual, and it seems that I'm only supposed to mess around with calibration settings on an empty tank. But is there any other way to 'undo' what I've just done, and tell the Command Link to go back to the previous calibration setting? I see an option for 'delete calibration', but I assume that's the same as what I just accidentally did. Or would that delete the new calibration that I just set, and return things to previous settings?

Thanks for any tips. I do not want to have to drain the tank in order to get the fuel gauge working again.

[boscoe99]

There is no going back. You can check out any time you like, but you can never leave.

Best way is to drain the tank and start over. Run the boat for as long as you feel comfortable so there is less gasoline to deal with. Then use a 12 volt electric pump to pump the tank dry. Put the gasoline in your truck as it is pumped out and fills a five gallon container. Then use the five point calibration procedure for best accuracy.

But given you don't want to do that you have two choices. Single point calibration or multi-point calibration. Both will require that the fuel tank sender be removed. Or the existing sender disconnected from the ships wiring so as to temporarily install another sender.

Actually, there are other choices. One being to run the tank as low as you dare. Then use the single point calibration method. Empty will not really be empty. When the gauge reads empty you will have a reserve remaining. The reserve being what ever amount you had in the tank when the gauge was recalibrated.

What is your pleasure?

[99yam40]

being he said it was his main tank , leads me to believe he has another tank in the boat.
just transfer the fuel from main tank to the other maybe an option.

I myself would prefer to use boat to burn the fuel or remove it thru the normal pick up tube so you know that is all you can pull out under running conditions and then call that empty even if there are a few gallons left in the tank.
Then calibrate using the most points allowed get the highest accuracy while filling up at the pump.

what size tank are you dealing with and how easy is it to get to the sending unit?

[rodbolt17]

why not either pull the fuel sender or attach another one so the system thinks the tank is empty. yall like to complicate things.

[boscoe99]

why not either pull the fuel sender or attach another one so the system thinks the tank is empty. yall like to complicate things.

Those are some of the options. Not the best options but they will work.

If someone is averse to draining a tank I suspect they will be averse to pulling a sender. Or buying a new one. And good luck doing a multi-point calibration with a sender out of the tank. Hard to know what resistance values equate to 0, 25, 50, 75 and 100 percent fuel quantities.

I like my fuel quantity indications to be spot on. As spot on as they can be. Some don't give a flip.

[Jonah272]

Thanks everyone,

I'm going to give this some thought. I don't have a spare sending unit to attach, so Rodbolt's idea isn't an option for me. For now, I know it has 40 gallons in there, so I'll burn it down to about 20 or 15 (15 would be 10%, which is where I'd expect the pickup tube to fail me), then reset again. I won't mind, temporarily, knowing that 0% is really more like 10%. Whenever I get the outboards serviced next, I'll make sure it has low fuel in the main, and ask the guys to pump the remainder into the aux, then do a proper calibration.

Thanks again.

[Jonah272]

Actually, what about this?

Assuming that the sending unit is just a pipe with a circular float around it, I could partially remove it so that the float drops, then re-calibrate to 0%. Since I currently have 25% in the tank, I could then replace the sending unit and continue with the next step of 5-point calibration, which happens to be the 25% mark. I could then continue with the calibration process, adding 25% each time.

Or, even simpler, just partially remove the sending unit so that the float drops, then do a single-point calibration to 0%?

I think this is what Rodbolt was getting at, which I may have misunderstood at first. Am I wrong in my understanding of how the sending unit works? On my previous Grady, it was as simple as the link below.

[pstephens46]

I was wondering the same thing. You can't just zero out the guage and sender and then be done? I have never fooled with mine. Just asking.

I do know my guage is off by about 20%. Gives me a 20% reserve.

[rodbolt17]

radio shack sells resistors all day long.
see what I mean. yall just like to make things complex.
place the resistor between the pink and black at the guage and you can tell it any level you wish.

[99yam40]

it would help to know what resistance represented zero and other spots of the sending units.

And Radio Shack has left town in a lot of places now.
we lost ours

[boscoe99]

Actually, what about this?

Assuming that the sending unit is just a pipe with a circular float around it, I could partially remove it so that the float drops, then re-calibrate to 0%. Since I currently have 25% in the tank, I could then replace the sending unit and continue with the next step of 5-point calibration, which happens to be the 25% mark. I could then continue with the calibration process, adding 25% each time.

Or, even simpler, just partially remove the sending unit so that the float drops, then do a single-point calibration to 0%?

I think this is what Rodbolt was getting at, which I may have misunderstood at first. Am I wrong in my understanding of how the sending unit works? On my previous Grady, it was as simple as the link below.

What you are proposing will work. Your sender could be one of several types. Ring on a vertical tube activating sensor switches, float on a stick moving a variable resistor or perhaps a modern capacitance probe. In either case with the sender out of the tank it will be simulating a zero fuel quantity. Or as you note, with the sender raised to the point so that it is not affected by any remaining gasoline.

[rodbolt17]

it is a standard 35-240 ohm. that is a US sender standard.
knowing at 35 ohms it will flow more current than 240 ohms I would use about a 220 -240 ohm resistance.
can be done at the pink and black wires at the guage.

[99yam40]

is 240 ohms full or empty?

[boscoe99]

is 240 ohms full or empty?

Nominally it is 240 ohms = full and 33 ohms = empty. But there are tolerances within each sender. Which is why to ensure the most accurate jury- rigged calibration setting it might be best to lift the existing sender from the tank and use that in lieu of a resistor.

Just depends upon how accurate one wants their fuel quantity indication system to be.

[zenoahphobic]

Reserve is good. Sometimes you might need the fuel gauge to read zero when some capacity left to cover for extreme tilt or even rough conditions when low fuel can cause the pickup to gulp air.
Too much reserve that is never used, is just additional unnecessary weight though.