Fuel guage pegged at "FULL"

[Bab]

Has any one had their fuel guage stick at the full mark? My last fill up has resulted in the guage going to the full mark each time I start the bike. I have rode it long enough so that the needle should have dropped some. At the present I have not begun diagnostics as I thought perhaps if I got down to approximately 1/2 a tank I could rock the bike and have the sloshing fuel dislodge the sender.

This is the first time I have had any issue with the bike since I bought it other than the usual maintenance. I love this thing, and again thank all of you who encouraged me to buy it so long ago.


Any thoughts, comments, or suggestions are appreciated...with thanks, Bab

 

[Fieroguy]

My gas gauge stays at FULL for the first 100 miles following a fill-up and then begins to move. So the effective 'range' of the fuel gauge is limited to the last half of the tank. At least it is on mine. It's a little disconcerting at first, but you get used to it over time.

 

[Miairhead]

My gas gauge always has read full for about the first 50+ miles, then drop to what I believe is correct level. I still am old school, and reset my mileage to 0 as I do on my 84 RT.

 

[Brillot2000]

The needle doesn't move for me typically between 70 to 80 miles driven. Be advised that the tank's interior is at a steep slope and the float reading will not have any linearity to the indicated value. Meaning that if the needle indicates 1/2 it may not be. I found that once the needle gets to the bottom of the "Red Zone" there's about a gallon left in the tank. However, only a 1/2 gallon of that is usable before the fuel pump cannot draw any below the cuff of the gasket base.

The fuel tank of the NT700 is very similar to that of the top tank of the ST1300, see below.

 

[Phil Tarman]

The fuel gauge is (sorta') accurate. It's repeatable and that's more important than being "accurate." My gauge usually starts to move at around 90-100 miles. Then it goes down pretty quickly. At 1/4 full I figure I've got 2 gallons left and can ride another 80-90 miles. You've still close to a gallon when it gets down to the bottom of the red.

 

[Macka]

A long time (years ago) I wanted to know the actual tank capacity.
To test the "usable" amount of fuel in the tank I have deliberately run the engine until it stalled due to lack of fuel.
Starting with a a completely dry tank (air dried), I put in 200ml (1 cup) of fuel and checked to see if the engine would start.
It started instantly and idled happily for 3 minutes at which time I turned it off.
I can declare accurately that the true tank capacity (filled until all air is bled out and the fuel is sitting in the upper filler neck) is 20.5 litres, not 19.7 as Honda says.
Filled to the bottom of the filler neck, it is about the claimed 19.7L.
The extra 0.8L will get me another 20km if I need it.
I have done 470+km (292 miles) between fill-ups, just once and still had some fuel in the tank.
It is very handy to know just how far you can go if you need to.
Often, here, fuel stations may be closed or have disappeared unexpectedly.
When touring I try to arrange my refills between 350 and 400km but this is not always possible.
Many smaller towns will not have any fuel supply and when off the main roads (where I like to ride) many are closed on the weekends.
On the other hand, I hate stopping very 150-200km for fuel as it is a waste of time.

I know that this does not help your gauge problem but it may be useful information for you.

Macka

 

[Macka]

Bab, further to my last post I have some more-useful information for you.
If you are handy with a multi-meter you can quick-test the tank unit without removing it.
Remove the seat, the rubber cover around the back of the tank and the LHS vent panel.
You should be able to see the harness from the tank.
It has a flat 3 wire connector about 1/3 of the way forward.
Unplug the connector and put your probes on the "Black/White" and "Red/Black" wires (on the tank side of the connector).
With the tank full you should have a resistance of 11-13 ohms.
With an empty tank it should be 271-276 ohms.
If you have around the 12 ohms and you know the tank is not full the float arm may be stuck at the top.
If you have zero ohms or very close to that then probably the resistor on the sender unit has failed and it will always show full.
If the float had fallen off the arm (virtually impossible) it would be showing empty all the time.
To test the gauge circuit from the connector forward you can just "ground" the Red/Black wire (forward side of the connector) to the frame or engine with the ignition turned on.
Grounded it should show Full. Ungrounded or Open Circuit it should show Empty.
Anything else indicates a problem in the gauge or associated wiring.

Macka

 

[Phil Tarman]

Bab, further to my last post I have some more-useful information for you.
If you are handy with a multi-meter you can quick-test the tank unit without removing it.
Remove the seat, the rubber cover around the back of the tank and the LHS vent panel.
You should be able to see the harness from the tank.

…..

This is what I love about this Forum!! There are people like Macka who know and understand the bike mechanically and electrically and can give useful advice when we've got questions. Thanks to you gurus! You're great!

 

[DirtFlier]

At least to me, the accuracy of the fuel gauge for the first 100+ miles is a moot point because I'm not going to stop for gas at that point. How it behaves in the final 1/4 is far more important.

ps. I've found that at 1/2 tank indicated on the gauge, it takes 2.6 gals to fill which is 1/2 of 5.2 capacity. When I first got the bike in Dec 2009, I did a lot of tests to see how much fuel it took from 1/2 tank, 1/4 tank, and needle sitting on E.

 

[Warren]

I have also found that at the 1/2 tank mark I have used 2.6 gallons. If you are averaging around 50 mpg that would give you approx 130 miles. While the fuel gauge might seem erratic I have found that is is actually quite accurate. You just have to learn how it operates especially when it gets down into the red zone. Once you figure it out it really only takes a quick look and you know where you stand as far as fuel amount and mileage remaining before empty.

 

[dnktng]

Look in the tank. I know, I know, why do that when there is a tank gauge.
Mine reads full on the gauge with the actual level 7/8" below the bottom of the filler neck, and 1 3/4" below the top of filler neck. Yes, I really did look in my tank AND I stuck a 6" steel rule in it.

I've learned that the NT tank can be filled ~.5 gallon more on the center stand vs. the side stand.....so their is a lot of variability based on the angle parked. Because of that, there is a lot of variability in how many miles it takes for the fuel gauge to come off of full.
1/2 gallon can easily be a 30 miles difference.

So again, before you start disconnecting and disassembling anything, I suggest looking in the tank.....like we did for years with motorcycles. It still works.

 

[Phil Tarman]

Look in the tank.

If you can't see into it very well, just don't use a match!

 

[Brillot2000]

If you can't see into it very well, just don't use a match!

Yeah, don't be like this guy that did.

[video=youtube;NlPbY1Vhw6k]https://www.youtube.com/watch?v=NlPbY1Vhw6k[/video]

 

[Bab]

Thanks every one for your quick responses. I've said it before, "you meet the nicest people on a Honda owner's forum".

I've had the bike since Oct. '14, and new I needed to run it for miles / kilometers until the guage would reflect the fuel consumption. I used to have a 40 minute commute to work, and got used to watching the guage, and knew it was accurate based on my observations, and also what I had read here. This year I haven't had the opportunity to run the bike as much as usual, and based on the bulk of the responses above, I may have suffered a simple brain fart, and just haven't put enough miles on it yet to see the float drop. I'll wait and see.

Special thanks to Macka ( I owe you a tinny) for his detailed diagnostics. This gives me a process of trouble shooting without having to crawl through the manual. I'll report the result of this when I know more...Bab

 

[Bab]

My fuel guage is functioning as normal. What is not normal is my riding habits this year. Obviously I'm not racking up the miles I usually do, got sloppy in watching my odometer, and panicked when I anticipated the guage movement prematurely. I should not have second guessed the reliability of this bike.


I thank all of you for responding and find it interesting how many different approaches to problem solving there are. Cool heads prevail, and you kept my feet on the ground so I could reason the situation through.

Best wishes, and kind regards to all...Bab