Whats going on with my fuel gauge??

Dinosaurbuilder · May 16, 2015

I thought everything was working ok but then I noticed the fuel gauge was staying on full, even with the wires disconnected from the tank it still stays full, and the low fuel warning light still comes on and goes off normally with the tank disconnected! should i be looking for a relay problem or a direct earth problem somewhere??

SMSW · May 16, 2015

Ground connections are probably the most frequent electrical gremlin out there. Other guys will weigh in soon with opinions on the reliability of the fuel sensor, but I would check the obvious and easy things first. A shop manual for your bike should show where the ground connections are for the instrument cluster and you might check these first.

I am assuming you don't have one of those magic tanks that refills itself as the fuel is consumed by the bike - thus always being full....

I like your avatar - good pic.

ST1100Y · May 16, 2015

Dinosaurbuilder said:
...I noticed the fuel gauge was staying on full, even with the wires disconnected from the tank it still stays full...

Definitely some wiring issues or maybe even a defective gauge; but I'd first check for ground issues, broken/cut cables, etc...
The low fuel warning is operated by a different circuit through an NTC-resistor, sitting on the fuel pump bracket.

Dinosaurbuilder · May 16, 2015

in my haste to evaluate the problem as soon as I got to work I forgot the sender unit is located on the side of the tank (We all love mornings) So I just checked the wiring on top .... oop's that was the fuel pump, I shall check the sender (on the side) on Monday and remember to drain the fuel if it needs changing.

the_gr8t_waldo · May 16, 2015

I think I would investigate the fuel level connector ( red bodied two conductor about knee high on left side) it's always seemed that that connector gets a lot of stresses/bending, that I think it's going to show up every time I put myown back. together.

Jim Van · May 17, 2015

I didn't know about that side connector either, the first time I removed my tank. Then I had to repair the broken wire .......

Interesting problem. Maybe your bike is possessed ........

Anyone know if the fuel sensor resistance decreases or increases as the tank empties ??

Gearjammer · May 17, 2015

Sounds like a problem I had. I poked a stick into the tank and found the fuel float was stuck. a quick poke soon released it and all has been well ever since.

dwalby · May 17, 2015

Jim Van said:
Anyone know if the fuel sensor resistance decreases or increases as the tank empties ??

Found this in another forum:

Honda state that the "Fuel unit resistance" which is to say the fuel gauge tank unit resistance should be:

At full level: 10 ohms
At Empty: 90 ohms

We checked Doug's 1996 and found the following:

Full (5-3/8" from top of float to fuel filler cap gasket surface on filler spout)- 12.7 ohms

8" from top- 24.8 ohms

10" from top- 38.3 ohms

12 from top- 52.6 ohms

Float at bottom of tank- 99.1 ohms.

Bush · May 17, 2015

The '96 I bought last summer was not reading the fuel level properly at first, until I removed the tank and dumped the old fuel out, with a few good shakes to get it all out while upside down. Now the fuel gauge works perfectly!

Dinosaurbuilder · May 18, 2015

All sorted, faulty sender unit, I had another tank with everything ok so I just swopped them over, although it's still saying full but if i push the float down the gauge goes down and that's with 3 UK gallons in from empty, but at leased I know there's fuel in the old gal.

ST1100Y · May 18, 2015

Dinosaurbuilder said:
...I had another tank with everything ok so I just swopped them over...

Good that you've solved the issue, but have an eye on the rubber gasket, or better even replace it with a new one... you don't want to find yourself and your bike in the dead centre of puddle with combustible liquid...

Dinosaurbuilder · May 18, 2015

ST1100Y said:
Good that you've solved the issue, but have an eye on the rubber gasket, or better even replace it with a new one... you don't want to find yourself and your bike in the dead centre of puddle with combustible liquid...

No Problem, I replaced the whole tank!!

Jim Van · May 23, 2015

dwalby said:
Found this in another forum:

Honda state that the "Fuel unit resistance" which is to say the fuel gauge tank unit resistance should be:

At full level: 10 ohms
At Empty: 90 ohms

We checked Doug's 1996 and found the following:

Full (5-3/8" from top of float to fuel filler cap gasket surface on filler spout)- 12.7 ohms

8" from top- 24.8 ohms

10" from top- 38.3 ohms

12 from top- 52.6 ohms

Float at bottom of tank- 99.1 ohms.

So, if the connector is disconnected , the gauge should read way below empty. And if the connector that goes to the gauge is shorted out, I would think the gauge should read way above full. The next time I have the left side cover off, I'll give it a try.

And if a resistance is added in series, you could make the gauge read exactly full ( not above full ) with a full tank of gas.

ST1100Y · May 24, 2015

Dinosaurbuilder said:
No Problem, I replaced the whole tank!!

LOL, so, depending on the condition of the reused item you're on the safe side then ;-)

Jim Van said:
And if a resistance is added in series, you could make the gauge read exactly full ( not above full ) with a full tank of gas.

Methinks bending the rod of the sinker is probably a more reliable (since KISS) solution there...

Brant · May 24, 2015

ST1100Y said:
LOL, so, depending on the condition of the reused item you're on the safe side then ;-)

Methinks bending the rod of the sinker is probably a more reliable (since KISS) solution there...

lol.....did that with my other listed ride, but it took three trys, removing and 'tweeking' the arm a bit.....you REALLY need to be bored to tears and in a fiddling mood though

.

ST1100Y · May 24, 2015

Brant said:
...it took three trys, removing and 'tweeking' the arm a bit.....you REALLY need to be bored to tears and in a fiddling mood though.

Which hasn't happened yet (the being bored out of my mind part...), which is why my fuel gauge needle still rests on the RHS limiter for the first ~90km after refuelling...

The only fuel instrument I took immediate care off was the NTC for the reserve warning... uh did I get busy fixing that... ;-)

Brant · May 24, 2015

ST1100Y said:
Which hasn't happened yet (the being bored out of my mind part...), which is why my fuel gauge needle still rests on the RHS limiter for the first ~90km after refuelling...
The only fuel instrument I took immediate care off was the NTC for the reserve warning... uh did I get busy fixing that... ;-)

My STeeds gauge follows that same pattern....close to same km/mi. before movement. Just used to it, and pay no never mind to it. But it IS dead-on on the lower end, half to empty.....DAHIK

.

ST1100Y · May 24, 2015

Brant said:
My STeeds gauge follows that same pattern....close to same km/mi.

The amount of fuel up in that "neck" cannot be monitored by the float... so the gauge remains on [full] till the level reaches the wide part of the cell...
The last 1/4 of fuel is another issue, the tank narrows progressively due the wheel arch...

But actually is that just nitpicking... ;-)

Brant · May 24, 2015

ST1100Y said:
The amount of fuel up in that "neck" cannot be monitored by the float... so the gauge remains on [full] till the level reaches the wide part of the cell...
The last 1/4 of fuel is another issue, the tank narrows progressively due the wheel arch...

But actually is that just nitpicking... ;-)

Not.......I try to run on upper half or nothing below a quarter tank. Pump will last lifetime of bike doing so, and already know mileage is constantly at 48-52mpg no matter LD cruisin' speed. Not that it matters, as mileage is fartherest from thought as to why I ride a scoot anyways

.

Dinosaurbuilder · May 25, 2015

Took her out for a run to work today, fuel gauge still hard over full but poking the float lower the gauge does go down ... so fill up at half a tank rather than quarter, or even old school and look in the tank ..... memories.