Fuel Gauge adjustment?

[Idaho Al]

My 08 FJR-A fuel use display is waaaaay off. The "time to fill-up light" starts flashing (and the trip miles changes to miles on reserve) after i have only used about 4 gallons. Each time i get paranoid and stop to fuel after about 45 more miles and sure enough... I only have to put in 5 gallons.

The "time to fill-up light" starts flashing when I still have 2 1/2 gallons left in the tank. Is there a way to reset the computor or does this show because of a float I need to bend.

I reset the trip milage and the Average MPG eash time and they both seem to be right on.

Any suggestions?

Alan (confused in Idaho)

 

[ionbeam]

The only practical way to fix the gas gauge is by mechanically bending the float arm by trial and error. There are some minor risks to doing this, mainly damaging things trying to get the pump/sending unit out of the tank. BkrK12 has done this to his FJR sending unit without things going wrong. I haven't looked into it but there may be a way to add an electrical 'calibrator' to the circuit.

Here is the tip of the iceberg for reading on the topic:

One

Two

Three

 

[FJR1300Mark]

Mine is much closer than yours but I still wondered how far I could go when it started counting up at the low fuel warning.

I kept a speadsheet on miles, gals, mpg, how many mile it counted up etc for a lot of miles. It varies depending on all the mpg parameters etc but I found out that on my bike I can ride 60 plus some little more miles on the low fuel count up and still have .5 gals left in the tank. I did a two lane road cross country last year and knowing exactly how much more fuel I had was comforting when the fuel stops could be 150 miles apart.

Keep track and you'll be able to know how your bike works.

 

[FJR Bill]

My 2009 starts flashing at just shy of 4 gallons useage. Meaning I got about 2.6 gallons remaining. I'll not try to fix it but rather use the odometer as my reference. I always get better than 40 MPG so, I'll know I'm getting low but with good margin at around 240 miles. I can live with that. I do agree tho that flashing symbol and mileage count is distracting. Bill

 

[Constant Mesh]

Replace the float with a larger one.

 

[RaYzerman19]

You could bend the float arm, but you could also just live with it. If you run it out of fuel a couple of times (carry a spare litre bottle), you will know how far to empty when the display starts flashing. If that doesn't keep you happy, then bending the float arm is the fix.

 

[ionbeam]

FWIW, the FSM says that both Gen I and Gen II the fuel sending unit in the tank should read 19-21Ω full and 139-141Ω empty @ 68ºF. Positive DMM lead on the Green/White wire and negative DMM lead on the Black wire. The span from min to max should always be 120Ω, but the range may be shifted up or down a bit so that it may be full at 10Ω and empty at 130Ω. --or-- 30Ω/150Ω.

The FSM says that you have to remove the tank to perform this check, (can't do this with the tank anything but level). There is another way, but you still will have to raise the tank twice. If you really are motivated to make this check I will post an option to removing the tank and draining it to make the resistance check. No matter what it's going to be a pain to check. Depending on what the intrepid troubleshooter finds, it may be possible to add an external electrical trim.

 

[Idaho Al]

Thanks for all the help. It does feel good to not have the only mutant fjr out there.

Alan

 

[Donal]

The only practical way to fix the gas gauge is by mechanically bending the float arm by trial and error. There are some minor risks to doing this, mainly damaging things trying to get the pump/sending unit out of the tank. BkrK12 has done this to his FJR sending unit without things going wrong. I haven't looked into it but there may be a way to add an electrical 'calibrator' to the circuit.

Sounds to me like there could be a 'market' for an 'electric calibrator'. This is one of those topics that re-appears on a regular basis. I would definitely be interested :clapping:

Don

 

[ionbeam]

...Sounds to me like there could be a 'market' for an 'electric calibrator'. This is one of those topics that re-appears on a regular basis. I would definitely be interested...

If you have a fuel gauge that is off by a lot bring your FJR over and I'll see what we can do. If someone that lives a bit closer and has less of a water crossing and has a similar gauge error send me a PM so we can get together and diagnose the problem and seek an electrical calibration solution.

 

[networkguy]

Mine starts flashing at about 4 1/2 gals.

 

[Constant Mesh]

Don't see how one could electrically calibrate it. When the float/arm is all the way down it's all the way down. Supposedly that's when the fuel gauge starts flashing. If you add some external resistance, series or parallel, the position of the arm is still going to control everything. When they tweaked the shape of the tank in '06 they probably didn't tweak/change the fuel gauge sender. The '06 tank has more fuel down low near the bottom so there's more gas left when the gauge starts flashing.

 

[Doug-InNC]

Mine starts flashing at about 4 1/2 gals.

This is an old thread but glad I found it. I recently purchased a lightly used 2008 and my light starts flashing at 4 1/2 gallons also. Glad to know I’m not the only one with this issue. The tank showing completely full only last about 2 1/2 miles, then my gauge drops the first mark.

 

[rbentnail]

Mine starts flashing at about 4 1/2 gals.

This is an old thread but glad I found it. I recently purchased a lightly used 2008 and my light starts flashing at 4 1/2 gallons also. Glad to know I’m not the only one with this issue. The tank showing completely full only last about 2 1/2 miles, then my gauge drops the first mark.

Yeah, my '07 has always been 4.8 gallons to fill up as soon as the indicator flashes. If the flashing indicators are annoying, I forget how much changes, I know the odometer goes back to normal, if you press the left button but I don't recall if the bars stop flashing. I typically fill up near-abouts when it starts flashing, I'm in the "keep the fuel pump well covered" camp. So far it's worked for me but it's only been 10.5 yrs/113,xxx miles so I guess I could be wrong.

 

[escapefjrtist]

My '15 typically shows "zero" range with ~ 4.8 - 5 gallons used. Although I never run into reserve, good to have a little left when gas could be a fair distance away. Thinking BFE Oregon! For the second piece, from full to first bar is around 20 miles.

YMMV

~G

 

[Uncle Hud]

^^^ My 2015 behaves just like G-Man's. (What a surprise!) And I'm thinking BFE Georgia, or Alabama, or North Carolina, or ... well, there's BFEs pretty much everywhere outside of New England.

 

[Fred W]

Don't see how one could electrically calibrate it. When the float/arm is all the way down it's all the way down. Supposedly that's when the fuel gauge starts flashing. If you add some external resistance, series or parallel, the position of the arm is still going to control everything. When they tweaked the shape of the tank in '06 they probably didn't tweak/change the fuel gauge sender. The '06 tank has more fuel down low near the bottom so there's more gas left when the gauge starts flashing.

I know I am replying to an old post here, but it made me think that perhaps there is a way to externally trim the fuel display. According to the even older post by ionbeam, the fuel sensor should be presenting 20 ohms resistance at full and 140 ohms when empty.
It would be quite easy to place a fixed resistance in parallel with the sending unit that would reduce the total resistance seen by the ECU, which would result in a higher gauge display at a given fuel level. Because the resistance at full tank is lower than at empty tank, the parallel resistance would have a proportionally larger impact at empty than at full.

The formula for parallel path resistances is : R1 x R2 / R1 + R2.

You can also cheat and just use this online calculator:

https://www.allaboutcircuits.com/tools/parallel-resistance-calculator/

So, as an example if we put a 3k ohm resistor in parallel with the sensor, at fully empty the ECU would see an equivalent resistance of 133.76 ohms (4.5% lower) and at full tank it would be 19.87 (only 0.7% lower).

There are a couple of things that would need to be determined before trying this. One is to experimentally determine the actual sensor resistance when the fuel gauge goes to reserve mode. It is probable that this happens at something other than at the sensors maximum resistance, otherwise even a small variation in the sensor resistance could result in the display never switching to reserve mode. You should also be able to determine how much fuel is left in the tank when the sensor bottoms out and hits its maximum resistance value of 140 ohms.

Should be able to get this data relatively easily just by fully emptying the tank and then making iterative resistance checks as measured amounts of fuel are added with the tank and bike level.

 

[Bounce]

Thanks for all the help. It does feel good to not have the only mutant fjr out there.Alan

This has been the case for every bike I've ever owned that included a fuel gauge. I just learn the bike and adapt with that often under-used mass between my ears.

 

[mcatrophy]

...Should be able to get this data relatively easily just by fully emptying the tank and then making iterative resistance checks as measured amounts of fuel are added with the tank and bike level.

I once went through this exercise on my '10, see here. I was going to use a microprocessor to linearise the reading, however I couldn't do what I wanted because there was too much dead zone both near full and near empty.