Gas Tank Gauge Issue...

Joined
Aug 23, 2022
Messages
350
Age
54
Location
Nova Scotia
Hiya All,

I asked about this on a FB group, but didn't receive information to help me resolve it. But I did learn something.

Here's the issue, followed by what I learned (if the information was accurate).

- A couple weeks ago I lifted the tank to check the air box and air filter. Air filter was still new-ish (only a couple thousand km) and still VERY clean, although I did remove it and blow air through it in the reverse direction to remove 1 small fly and 1 dandylion "parachute" seed. Some dust came out, too. Some of you will likely caution and hate me for this but I'll take it as it is. The air filter is good. I also checked the snorkels to ensure there were no critters of any sort. They were fine. And I cleaned the oil overflow (oil change had been done recently and perhaps he slightly overfilled, which was likely good because it dripped oil for at least a week until I brought it to my local auto mechanic only 30 seconds away from my house who tightened the drain bolt - the oil changing motorcycle "professional" didn't tighten it enough and told me, "Sometimes they drip for a few days, but it will stop." BS!! Thanks for a sub-professional job and for not taking responsibility. Now I have a big patch of oil on my concrete driveway! Does anyone know what I can do to "dissolve" or remove this oil patch...?? I tried oatmeal and sand, but they did nothing.)

- So, after completing my airbox maintenance, the next time I ran my tank down to low, the digital display stayed on 3 bars for a LONG time, then it jumped to a single flashing bar. It bypassed the 2 flashing bars completely. Since then, it completely bypasses the 2nd bar, but it does stay "stuck" on 3 bars for a LONG LONG time.

What I learned: Someone on a FB group stated the the ST13 gas tank has two gauges - one float style gauge in the upper tank, then an electronic sensor gauge in the lower tank. It was suggested that the float gauge somehow got into a position where it gets stuck at the 3 bar position instead of continuing to sink lower to yield a 2 bar position.

This seems logical, and that my most recent maintenance operation, possibly due to the amount of gas in the tank, unfortunately put the float in a non-ideal position causing it to act this way. I would be surprised if something actually "broke down", since this bike is a 2014 single owner (likely purchased in 2015 or perhaps even 2016) low km well-maintained garage-winter-kept bike that, in spite of my various diagnostics, has not shown anything at all to be flawed.

IF indeed the float is simply stuck in a bad position, is there any simple way I could dislodge it and free it up to normal operation. I was thinking of "fishing" with a 10 gauge stiff electric wire (of course cut carefully enough such that the copper is not protruding at all from the insulation, and such that there will be ZERO chance of scratching since the plastic insulation would be the only portion contacting the inside tank walls).

Thanks in advance for any thoughts!

(Oh, and please don't bother responding if you're just gonna say, "oh, I don't follow my gauge at all... I just check the amount of km I drive," or "gauges are approximate anyway, don't use them". Those answers are NOT helpful at all. I want to FIX it, not learn to just live with something that is broken. The gauge was working PERFECTLY until I noticed the difference after my recent maintenance. Thank you!!!)
 
I use Cat litter, the stuff you put in their wee/poo tray.

Had same problem with the Sender unit in the top main tank, long story cut short is ~ took out the Sender unit and reconnected the plug, turn on ignition and move the float up & down.
Note how the gauge reads at the different levels - you might need to carefully clean the segments with fine wet & dry.
 
I use Cat litter, the stuff you put in their wee/poo tray.

Had same problem with the Sender unit in the top main tank, long story cut short is ~ took out the Sender unit and reconnected the plug, turn on ignition and move the float up & down.
Note how the gauge reads at the different levels - you might need to carefully clean the segments with fine wet & dry.

Thanks! This is obscure to me. I'll have to check this in my repair manual. FWIW, how challenging is it to remove the "sender unit"...?
 
I use Cat litter, the stuff you put in their wee/poo tray.

Had same problem with the Sender unit in the top main tank, long story cut short is ~ took out the Sender unit and reconnected the plug, turn on ignition and move the float up & down.
Note how the gauge reads at the different levels - you might need to carefully clean the segments with fine wet & dry.

Ooof!!! I just checked the repair manual. For me, this is a MAJOR operation to access the float... Damn!!! Wonder if there's anything I can try with the tank still installed...??
 
While the arm/float may be sticking, its more likely caused by a film of corrosion on the face of the unit.
Carefully remove it, and take a soft pencil eraser and gently clean the surface, and put it back together.
You'll find its working again.
Be very careful not to pinch wires, or damage the lower tanks sealing lip.
Also be very careful not to over torque the fasteners on the studs on the lower tank.
There is also a sequence that is different between years in the pattern you tighten them in, check your service manual.
I would caution against using a torque wrench, unless you have a very high quality one, that has been calibrated recently for inch pounds.
Search the forum for these issues.
20201227_115650.jpg
 
Ooof!!! I just checked the repair manual. For me, this is a MAJOR operation to access the float... Damn!!! Wonder if there's anything I can try with the tank still installed...??
You could start by running some seafoam through the system in an attempt to try and clean the varnish off the face of the unit.
 
While the arm/float may be sticking, its more likely caused by a film of corrosion on the face of the unit.
Carefully remove it, and take a soft pencil eraser and gently clean the surface, and put it back together.
You'll find its working again.
Be very careful not to pinch wires, or damage the lower tanks sealing lip.
Also be very careful not to over torque the fasteners on the studs on the lower tank.
There is also a sequence that is different between years in the pattern you tighten them in, check your service manual.
I would caution against using a torque wrench, unless you have a very high quality one, that has been calibrated recently for inch pounds.
Search the forum for these issues.

Thanks for this I.Go.Far. It looks like a specialized potentiometer. Damn though, it's quite a job to remove!! I don't trust any of my local Wrenchers to do what is quite clearly to me a delicate operation. The cleaning of the part is VERY much within my specialty... I build and repair guitars, and my margin of error is down to a thousandth of an inch or less at times (ie: guitar rosette with 0.4mm rosette pixels, totalling approximately 7500 discrete pieces of wood in one rosette, and I also work on guitar electronics). I wonder if the Lucas fuel additive I used could have built up a film on this part - it is a very viscous additive compared to others I've used, but was recommended by a motorcycle Wrencher (the same guy who scratched up my rim using crow-bars to change my front tire, and who didn't tighten the oil drain bolt properly causing my oil to leak for a week or more, and he gave the excuse, "It sometimes leaks for a few days but it will go away!") But for me, I am TOTALLY not an expert in disassembling the bike and it gives me anxiety paralysis.

I wonder if there's another additive I could use that might help, if indeed it is a "film" buildup...

Hmmm... Lacquer thinner....?? (It is similar, or equal to, the liquids used to clean cats...)
 
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I use solvents like Kerosene and WD40 to clean anything oil and grease related, even off my concrete garage floor. It may be too harsh for your driveway,not sure, thought I would suggest it.

I've never had the fuel sending unit out either, but I believe you just remove the fuel tank and unbolt it from the bottom. Running some cleaners like Seafoam suggested above would be a good "non evasive" first step. :)
Good luck....
 
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Senior Moment :rofl1:
I should not work on replacing a fuel pump, (looking at it) while I'm answering a post about the sending unit.
My bad.
Mr. E is correct, the sending unit is in the upper tank, and the upper tank can be removed by three fasteners, a fuel joint hose, and a couple connectors, which is relatively easy.
However, you should have a NEW fuel joint hose standing by, as the old hoses get hard, and crack like plastic.
There is one large O-ring under the unit, that is held in place by four nuts.
No torque is needed for these, just snug them town, and inspect the O-ring.
 
You could start by running some seafoam through the system in an attempt to try and clean the varnish off the face of the unit.

I've used Royal Purple, STP, and I tried Lucas Fuel additive (but I don't want to use Lucas anymore since it seems very viscous). Royal Purple seems to have given good results with improving fuel economy. Seafoam makes a couple different types of additives, viscous and "thin". I expect their "thin" formulation is similar to Royal Purple. I wonder, as I posted in reply to Igofar above, if the Lucas additive helped add a film...
 
Senior Moment :rofl1:
I should not work on replacing a fuel pump, (looking at it) while I'm answering a post about the sending unit.
My bad.
Mr. E is correct, the sending unit is in the upper tank, and the upper tank can be removed by three fasteners, a fuel joint hose, and a couple connectors, which is relatively easy.
However, you should have a NEW fuel joint hose standing by, as the old hoses get hard, and crack like plastic.
There is one large O-ring under the unit, that is held in place by four nuts.
No torque is needed for these, just snug them town, and inspect the O-ring.

Gotta run for now... But thanks for this... I'll review later, and try to understand, and follow with questions if it's still Greek to me.

Appreciate you sharing your knowledge in effort to help... And appreciate every one else in this thread sharing to try to help.

I'm a lucky man! Life is good! Thank you!!!
 
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Does anyone know what I can do to "dissolve" or remove this oil patch...??
No personal experience, but in researching this very question the below product came very highly recommended. As I recall, it was developed by university of B.C. professors specifically to prevent oil stains from being washed down the sewers in to the waters of B.C.
Oil Lift

As for the fuel gauge, it caused by an intermittent or failing connection of the sender segment that reports that level of fuel. It can be a mechanical problem that requires replacing the sender unit, but it also can be caused by contaminants such as varnish in fuels. I had the same issue and resolved it without any invasive measures. Maybe you will be as lucky. Below is what I did.

I added one full bottle of SeaFoam to a full fuel tank. This is double the recommended dosage per the instructions but it will not cause any harm whatsoever or any drive-ability issues.

I let the SeaFoam sit in the tank as long as I reasonably could. I avoided using mine Monday through Friday while I was at work and let it soak.
On the weekend I used it for my normal weekend riding. At every fill up I added 1/2 bottle of SeaFoam, which is the recommended amount for the quantity of fuel in an ST1300 tank. I did this so that there would always be at least the minimum recommended SeaFoam concentration in the fuel to keep the cleaning process ongoing.
At the end of the weekend I added another full bottle of SeaFoam, filled the tank and parked the bike again to let it soak Monday through Friday.
After that second soak I ran one more bottle of SeaFoam through the tank at the normal dosage of 1/2 bottle per tank.
After that I used the motorcycle normally without any more SeaFoam.

In my case the SeaFoam cleaned off whatever contaminant was preventing the sending unit from registering at that spot and the gauge worked normally again. That was quite a few years ago and that problem has never resurfaced. Easy to try and doesn't cost much. Hopefully you will be as lucky.
 
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Had the same problem, I took out the sending unit In the top tank and cleaned it with an abrasive eraser-cleared it right up.
I checked it before and after with a DVOM. Checked out fine after cleaning.
 
No personal experience, but in researching this very question the below product came very highly recommended. As I recall, it was developed by university of B.C. professors specifically to prevent oil stains from being washed down the sewers in to the waters of B.C.
Oil Lift

As for the fuel gauge, it caused by an intermittent or failing connection of the sender segment that reports that level of fuel. It can be a mechanical problem that requires replacing the sender unit, but it also can be caused by contaminants such as varnish in fuels. I had the same issue and resolved it without any invasive measures. Maybe you will be as lucky. Below is what I did.

I added one full bottle of SeaFoam to a full fuel tank. This is double the recommended dosage per the instructions but it will not cause any harm whatsoever or any drive-ability issues.

I let the SeaFoam sit in the tank as long as I reasonably could. I avoided using mine Monday through Friday while I was at work and let it soak.
On the weekend I used it for my normal weekend riding. At every fill up I added 1/2 bottle of SeaFoam, which is the recommended amount for the quantity of fuel in an ST1300 tank. I did this so that there would always be at least the minimum recommended SeaFoam concentration in the fuel to keep the cleaning process ongoing.
At the end of the weekend I added another full bottle of SeaFoam, filled the tank and parked the bike again to let it soak Monday through Friday.
After that second soak I ran one more bottle of SeaFoam through the tank at the normal dosage of 1/2 bottle per tank.
After that I used the motorcycle normally without any more SeaFoam.

In my case the SeaFoam cleaned off whatever contaminant was preventing the sending unit from registering at that spot and the gauge worked normally again. That was quite a few years ago and that problem has never resurfaced. Easy to try and doesn't cost much. Hopefully you will be as lucky.

Thank you for this.

Lots of SeaFoam products:


Which did you use...?? I've only used this one so far for SeaFoam brand:

 
Had the same problem, I took out the sending unit In the top tank and cleaned it with an abrasive eraser-cleared it right up.
I checked it before and after with a DVOM. Checked out fine after cleaning.

Thank you!! Perhaps I'll try more concentrate SeaFoam treatment as per Andrew Shadow's suggestion first. But I'm glad to know it is likely a fairly easy fix.
 
I use solvents like Kerosene and WD40 to clean anything oil and grease related, even off my concrete garage floor. It may be too harsh for your driveway,not sure, thought I would suggest it.

I've never had the fuel sending unit out either, but I believe you just remove the fuel tank and unbolt it from the bottom. Running some cleaners like Seafoam suggested above would be a good "non evasive" first step. :)
Good luck....
Thanks again!
 
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