Interesting observation on the low fuel sensor

T_C

Joined
Mar 8, 2012
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4,341
Location
St. Louis, MO
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2005 St1300
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8568
The whole low-fuel indicator and how it sometimes rests and sometimes doesn't has been discussed, theororized and wondered about. But I had a new bit of evidence presented to me the other night.

Heading home I was low on gas, light was flashing. I was stopping but worried about my battery being low. Weighing the risks I decided to stop for a partial fuel-up and leave the engine running (yes, I said it). I carefully poured in 3.5 gallons and when I looked at the dash to record my mileage I noticed the fuel gauge was still flashing low. I finished up my record keeping and the low light was still flashing. Geared back up and took off, half a mile down the road the system finally updated and showed a half tank.

So if the system is only polling the fuel sensors every minute or so is that why sometimes the thermistor will get reset and sometimes it doesn't? The thermistor doesn't just measure the temperature but it's measuring it's own heat dissipation (something it can do faster in liquid it can't do in air). Bit if not being continuously being polled... hmm...
 

ST Gui

240Robert
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Sep 12, 2011
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SF-Oakland CA
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ST1300, 2010
yes, I said it
:rofl1:


T_C said:
I noticed the fuel gauge was still flashing low. I finished up my record keeping and the low light was still flashing. Geared back up and took off, half a mile down the road the system finally updated and showed a half tank.
So at this point this is about how often the the gauge is updated? Can you confirm/estimate independently via your record keeping how much gas you had at that point? Or can we assume it was and is correct.

My last question— since you kept the bike running while gassing up did you have a short-key knob or the more pedestrian spare key? Or a non-locking gas cap.
 
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T_C

T_C

Joined
Mar 8, 2012
Messages
4,341
Location
St. Louis, MO
Bike
2005 St1300
STOC #
8568
Short key set-up on the saddle bags and left toaster box, so ignition always stays in place, but normally turned off, unless I walk away for refreshments or personal relief.

Outside temperature was at the freezing mark and my battery had failed a few times earlier to start the bike, so I knew it was a potential to happen again. This particular gas station had no hills for me to roll down, so a careful partial fill-up while engine running was my solution. I had a replacement battery at the house, but it was a long cold walk away.

Yes, I can confirm that the dash gauge was correct. It was my third day of commuting to work so I would have been at 300+ miles from my last full fill. I was into the final gallon of fuel, flashing last bar was fully expected. Not expected was the 3~4 minute delay in the fuel on-board display update. I dumped in 3.5 gallons of cold fuel and had time to enter the data on my phone, put winter gloves back on, exit the station with a left turn on a busy road and drive a half mile before seeing the change.
 
Last edited:
Joined
Apr 9, 2011
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1,024
Location
Canton, GA
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2006 ST1300
Normally, you'd have the engine off, and then fuel it, THEN turn the engine back on, with all the settings being updated , rebooted, etc. Mine always takes a second even after starting to come up to full.
 

thekaz

haz gone feral
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Jul 29, 2014
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canadian west coast
never thought of this on my ST1300 BUT in modern vehicles having the key on while fueling will cause the "anti slosh" logic to get confused. Sometimes taking 20 minutes ( post 2015 GM cutaways ) to read accurately.
my guess is the ST1300 may have the same kinda logic via electronics ?
 
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