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Offline v8guy

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Low fuel sensor failure
on: August 15, 2019, 09:20:37 PM
Over the last four or five refills, my bike's low fuel sensor has apparently given up on me. No warning lamp, and no flashing fuel level on the LCD. At the same time, it's started to develop a vacuum in the tank so when I refill I get a sharp intake of air as I lift the cap. Possibly related?

After the recent 16k service, the vacuum issue was present so I had my mechanic lift the tank and free up the hose.. all good until recently. Not had any reason to lift the tank since.

Any ideas?
Current: BMW R1200RS, 2003 Yamaha TDM900
Past: Honda CLR125, Honda CB500, Triumph Sprint Sport, Honda VFR750FS, Suzuki DRZ400SM, 2001 Triumph Speed Triple 955i, 2015 Honda VFR800X

"Being shot out of a cannon will always be better than being squeezed out of a tube" - HST

Offline AndrewP

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Re: Low fuel sensor failure
Reply #1 on: August 15, 2019, 10:06:47 PM
I've got the vaccum behaviour you mention since I first got the bike, but both fuel indicator and low fuel light work just fine.

Maybe the fuel level sensor is malfunctioning to the point where the float doesn't reach it's lowest point?
And the Lord said unto John, “Come forth and you will receive eternal life.”
But John came in fifth - and won a toaster.

Offline v8guy

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Re: Low fuel sensor failure
Reply #2 on: August 16, 2019, 10:45:34 AM
*Originally Posted by AndrewP [+]
I've got the vaccum behaviour you mention since I first got the bike, but both fuel indicator and low fuel light work just fine.

Maybe the fuel level sensor is malfunctioning to the point where the float doesn't reach it's lowest point?
The vacuum is most likely caused by a trapped/clogged breather hose, as happened to mine after the service.

I'm curious about how the low fuel sensor actually works... maybe I need to access the service manual.
Current: BMW R1200RS, 2003 Yamaha TDM900
Past: Honda CLR125, Honda CB500, Triumph Sprint Sport, Honda VFR750FS, Suzuki DRZ400SM, 2001 Triumph Speed Triple 955i, 2015 Honda VFR800X

"Being shot out of a cannon will always be better than being squeezed out of a tube" - HST

Offline AndrewP

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  • Bike: 2015 VFR800X
  • City / Town: London
  • Country: United Kingdom
Re: Low fuel sensor failure
Reply #3 on: August 16, 2019, 12:10:40 PM
Dumbing it down, it works similar to a toilet reservoir.

It's got a float which is attached to a sensor. As the fuel level goes down, so does the float and the sensor then sends the level readings to the ECU.

That's why sometimes if you have the bike on the side-stand or on an slope you won't get an accurate reading on the remaining fuel until you start riding.

I'll make sure to get them to check the vaccum issue during my next visit.

Edit: this is the sensor for a 02-09 VFR: https://www.ebay.co.uk/itm/Honda-VFR-800-RC46-Fuel-Level-Sensor-/232536685106
Last Edit: August 16, 2019, 12:14:00 PM by AndrewP
And the Lord said unto John, “Come forth and you will receive eternal life.”
But John came in fifth - and won a toaster.

 



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