Riddle Me This: Same MPG, Lower Range

[Scooter]

The one thing that Mr. Pie Emeritus has not disclosed yet is how does he define "out of fuel". He does mention this...

Or, is the fuel indicator blinking earlier due to a new angle, but I actually have more fuel than would normally trigger the blinky last light?

So I will assume that he waits until the display is showing one flashing bar. The diagram in the service manual on page 24-7 (2003 edition) shows the point at which the display transitions over to the flashing last bar. Which, in my interpretation, would indicate when the level in the lower tank reaches the point where the thermocouple (which Honda calls the fuel reserve sensor) has just become exposed and I would think that the position of the fuel level sensor in the upper tank would have been in its lowest position for some long period of time, i.e., should not have any bearing in the determination as to when the computer decides to indicate the flashing bar (have I lost you yet?).

However, the manual does state the following...

When the fuel reserve sensor is turned on, the travel computer detects a signal from the fuel level sensor, and calculates possible travel distance, based on the amount of fuel remaining and the fuel consumption for 20 minutes immediately prior to the fuel reserve sensor turning on. When this happens, the fuel level meter begins to blink the final segment.

So if I had to guess based on what the manual just stated I'd go along with Sennister and say that there is something different about the fuel level sensor that you changed last year. Other possibilities, one: did you ever remove the cable bundle that attaches to your dash? Two: something has changed with the lower tanks fuel reserve sensor (unlikely)

FYI. The manual shows that when the final segment starts to blink that there will be 4.2 litres of gas remaining (1.11 gallons US) which means that you should be putting in roughly 6.3 gallons when you fill up assuming you refuel at that time. [This value will be different depending on how you fuel your bike: sidestand vs center, which "bar" you use as the top off point (I see two), etc]

Enough blabbing for now... :

 

[RCS]

Alex, I'll take fuel sensor alignment for $500...

If your MPG is the same, and your measuring it the old fashion way - miles driven divided by gallons used - I'd say something is up with your fuel sensor that triggers the blinking light. It could be the sensor or geometry - the angle of the bike with the new tires and/or maybe you've blown the preload on the rear shock and/or maybe some additional weight has been added to the rear of the motorcycle...maybe one too many pieces of pie.

 

[EASt]

There is one other possibility that relates to the hammer theory and that is that the new fuel sensor is larger (displaces more fuel) than the old one. A larger float perhaps?

Now there's an interesting thought. Personally, I doubt Honda would make a change of this sort, but it's certainly possible!

While the issue isn't enough to make me replace my float sensor again, it's really a bizarre scenario that has perplexed me every time I fill up (usually around 260-270 miles).

Earlier, someone mentioned that the bottom set of indicator bars tend to "hang on" longer than the top half. I think my indicator has always been that way, but since the suspension (and float replacement) the last three bars REALLY hang on tight before dropping.

 

[Scooter]

I understand the manual differently. The point you make above when the miles to empty pops up is when the last fuel bar starts to blink. that readout of miles to empty changes to dash marks when the thirmister is uncovered.

If this were the case the diagrams shown in the service manual are incorrect. The key figure in this is the middle diagram which shows the fuel level sensor resistance versus the function of total tank capacity. The key point being is that the lowest point shown on the graph is when the fuel level sensor has bottomed out and yet there is a significant amount of time that passes before the last blinking bar appears and corresponds exactly when the level of fuel remaining in the lower tank is right where the thermocouple is located. I believe that the readout changes to the dashed lines is determined solely by the calculations performed by the travel computer based on the fuel pulse signals sent to the ECM. The last pictorial shows that the level of fuel in the lower tank is way below the location of the thermistor. Maybe I'll make a copy of the diagram and post it but I'm not sure if the mods would allow it to stay up on the site...

 

[Scooter]

Perhaps the float bar was bent during shipment or "shudder", installation...

 

[sennister]

While a different float crossed my mind I doubt the would make one big enough to account for about 1/2 gallon.

Clearly only a hammer could take up that much volume.

It was my understanding that two bars activate when the upper sensor indicates no fuel left based on resistance in the sending unit. The blinky count down to blistered feet doesn't start until the thermocouple is exposed.

So do you take it that low Erik? What is the trigger in your mind that says time for gas. Everyone is different. Personally I always top off when I get to 2 bars or shortly after. It is rare that I ever see the blinky fuel gauge but that is me.

I would agree that my first bar or two is gone pretty quick. It is those middle bars that last a long time for me.

 

[sennister]

Perhaps the float bar was bent during shipment or "shudder", installation...

I kind of was thinking this. From what I recall from his posts before he did install it without pulling the tank. Again that is from memory of a post a while back. I wasn't there and I don't know how easy of a task that would be. I can see how a hammer would get in the way of the float's range of motion and cause the issue though.

 

[EASt]

Well, if anybody on this site was going to mess up the fuel sensor during install, it'd be me. Another likely cause.

FWIW: I followed the manual procedure to replace the sensor. I pulled the tank.

For me, I start sniffing for fuel stations around 250miles. Real close to blinky time. When blinky is going, I'll stop at the next convenient station.

Unless I'm in Utah. There, I fill up at every station I see, even if it's only been 10 miles since my last. To a guy from the Land of 10,000 Lakes, that state scares the carp outta me.

And, Dave, if I were the kind of rider who could actually lean a motorcycle, I reckon the hammer would make a 'clunk' when I turn. As I ride like a priss, we'll never be able to verify using this method.


Sent from my iPhone using Tapatalk

 

[EASt]

The upper FSU is a real piece of carp. I'm on my second unit and, immediately after a fill up, it shows one bar missing. It just started this a few months ago and not when I replaced it a few years ago. I just use that as a guide and not on how much fuel is actually in the tank.

My original FSU never had this problem. My new one does, though. I lose the first tick on the gauge after roughly 10 miles on the odometer.

 

[sennister]

My original FSU never had this problem. My new one does, though. I lose the first tick on the gauge after roughly 10 miles on the odometer.

Hmm that is fast. When I say my first tic drops fast I would say it is in the first 25-40 miles depending on where I am riding (back road twisties or slabbing it). I wonder if the hammer is stuck to the top of the tank and is keeping the float from going all the way up? Do hammers float?

 

[EASt]

Some hammers do float, but typically they have an appropriate age range on the packaging.