Been doing some test runs on my bike which has sat for years.Keeping and eye on fuel gauge to check mileage and the needle is well into the red but the fuel idiot light has not come on.Powers up at start up and goes out as it should,but should go on at 1.3 US gal left in tank.Can I be in the red and still have that much?How do you check it if it doesn't come on.Planning to throw a half gallon in a container and drive around town till she runs dry,....
Low Fuel Light,How to Check.
- Thread starter mznyc
- Start date
I seem to recall that when at the threshold, when the gauge needle is around the little white line next to the E, that the low fuel light will flicker on/off when accelerating or on uphill slopes. That's about 1.3 gals left like you say, mine usually hits the white line at about 6 gals consumed. As you push the needle more into the E area then the light will illuminate more steadily, so if yours isn't even flickering on/off by that point it may have issues.
The service manual is a bit vague regarding troubleshooting this system, and it primarily deals with what to do if you don't get the on/off sequence that you're getting upon startup. There's only one wire pair coming from the tank, so it appears that same signal is used for both the gauge and the light. there's a little module in the front fairing that controls the light, but it doesn't say anything about how to test it other than to measure that its getting 12v to its connector.
Maybe someone else has had to troubleshoot this and can give you further instructions, but if not I'd probably just use the gauge and forget about it.
The service manual is a bit vague regarding troubleshooting this system, and it primarily deals with what to do if you don't get the on/off sequence that you're getting upon startup. There's only one wire pair coming from the tank, so it appears that same signal is used for both the gauge and the light. there's a little module in the front fairing that controls the light, but it doesn't say anything about how to test it other than to measure that its getting 12v to its connector.
Maybe someone else has had to troubleshoot this and can give you further instructions, but if not I'd probably just use the gauge and forget about it.
If I'm not mistaken the light is seperate from the gauge.
The gauge is fed through a connector on the side of the fuel tank while the fuel light is connected to one of the connectors on 'top' next to the fuel pump connector.
The gauge is fed through a connector on the side of the fuel tank while the fuel light is connected to one of the connectors on 'top' next to the fuel pump connector.
ST1100Y
Site Supporter
Yep, completely different circuit...
There is an NTC on the bracket of the fuel pump, as long as submerged, thus cooled by liquid it has several hundred Ohms, therefore no idiot light...
Once the NTC is exposed to "vapour only" it warms (slightly), causing its resistance to go near zero, thus the light comes up.
If it stays dark, either the bulb is gone, the wiring is open somewhere or that NTC has died.
Thanks guys
Martin,What's an NTC?
You may have missed that I said the light comes on at start-up as it should then goes out as it should.
I assume I'll have to pull the fuel pump to inspect the NTC,which means I will have to replace gasket if I do?
Thanks
Michael
Martin,What's an NTC?
You may have missed that I said the light comes on at start-up as it should then goes out as it should.
I assume I'll have to pull the fuel pump to inspect the NTC,which means I will have to replace gasket if I do?
Thanks
Michael
John OoSTerhuis
Life Is Good!
Here's some info on the low fuel sensor (thermistor):
http://www.st-riders.net/index.php?topic=976.msg8135;topicseen#msg8135
http://www.st-riders.net/index.php?topic=976.msg6775;topicseen#msg6775
http://www.st-riders.net/index.php?topic=976.msg8135;topicseen#msg8135
http://www.st-riders.net/index.php?topic=976.msg6775;topicseen#msg6775
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great info John, way better than the service manual.
BTW, the picture in the Honda manual only shows one electrical connector coming from the tank for the level sensor, are both circuits in that single connector? I seem to remember only that one and the one to the fuel pump when I pulled the tank last year.
BTW, the picture in the Honda manual only shows one electrical connector coming from the tank for the level sensor, are both circuits in that single connector? I seem to remember only that one and the one to the fuel pump when I pulled the tank last year.
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John OoSTerhuis
Life Is Good!
I'm not sure, and I'm not near the garage and service manual.
Just noticed Carroll's pictures and Tom's schematic are missing from the AOW. I can contact my friend Tom about that if anyone's interested. There's a LOT of broken links after Webshots changed to Smile.
John
via iPhone 4S
Just noticed Carroll's pictures and Tom's schematic are missing from the AOW. I can contact my friend Tom about that if anyone's interested. There's a LOT of broken links after Webshots changed to Smile.
John
via iPhone 4S
Aha, I looked at the schematic again, last night I was a bit blurry eyed, and mistraced the path. Now I see the thermistor in the path, and the circuit appears to be connected by the connector to the fuel pump, just like Martin mentioned earlier.
Sorry about the original misinformation.
BTW, to the OP, in thermistors NTC stands for Negative Temperature Coefficient, which means the resistance goes down as temp goes up.
Sorry about the original misinformation.
BTW, to the OP, in thermistors NTC stands for Negative Temperature Coefficient, which means the resistance goes down as temp goes up.
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OK had a look inside.
Definitely less than a gallon in there.Unfortunately some rust sentiment in there also.Filter is new but I'll have to clean tank and replace filter and pump gasket,.... If not more,...
Bottom of the tank looks clean but some evidence around neck of the filler,and with long layup probably built up over time and disturbed it when I filled it for the first time in a hlf decade recently(ya should have had a look before she went back into bike),won't be sure until I pull pump,...
As far as KoTAOW's check,He says short the Brown/Blue wire to a ground point.Mine's Brown/Black,probably a MY difference? Also can't get the bugger off.During the restoration I've connected and disconnected it several times pulling the tank but don't have the touch now,sure it's counter intuitive.Any suggestions?
"A quick test of the low fuel light circuit is to short circuit the sensor connector (the Brown with Blue striped wire lug next to the green wire ground lug on top of the fuel pump assembly located under the seat) to ground with a screwdriver or knife blade with the ignition key on. If your fuel light comes on, the bulb and circuit wiring are OK. Just be sure you short the BROWN with BLUE striped wire and NOT the brown with red striped wire which is the 12vdc power to the pump!"
Definitely less than a gallon in there.Unfortunately some rust sentiment in there also.Filter is new but I'll have to clean tank and replace filter and pump gasket,....
If not more,...Bottom of the tank looks clean but some evidence around neck of the filler,and with long layup probably built up over time and disturbed it when I filled it for the first time in a hlf decade recently(ya should have had a look before she went back into bike),won't be sure until I pull pump,...
As far as KoTAOW's check,He says short the Brown/Blue wire to a ground point.Mine's Brown/Black,probably a MY difference? Also can't get the bugger off.During the restoration I've connected and disconnected it several times pulling the tank but don't have the touch now,sure it's counter intuitive.Any suggestions?
"A quick test of the low fuel light circuit is to short circuit the sensor connector (the Brown with Blue striped wire lug next to the green wire ground lug on top of the fuel pump assembly located under the seat) to ground with a screwdriver or knife blade with the ignition key on. If your fuel light comes on, the bulb and circuit wiring are OK. Just be sure you short the BROWN with BLUE striped wire and NOT the brown with red striped wire which is the 12vdc power to the pump!"
ST1100Y
Site Supporter
So the lamp is fine, the check circuit working.
When the NTC on my '00 ST gave in I got a complete '94 pump assy at Ebay for way less then I would have gotten any compatible low fuel sensor (about € 54,- delivered) and it saved me the hustle of having to tinker with the soldering iron for swapping that NTC canister.
I first tried to "get away" by carefully cleaning my old gasket, applying a slight smear of silicone-grease and putting it on the donation-pump, but no avail... started to seep instantly once the fuel level hit it... (figured that out right after installation by shaking the bike with removed seat...)
P/N 17574-MN5-000 doesn't cost much and gives peace of mind...
Good point Martin buying the while assembly.We have a group discount here n the States,would probably apply to you also,but figured shipping and taxes wouldn't make it worth while,from a dealer here,so would probably get them cheap,I'll check prices.Don't see it listed on the parts fische,http://www.bikebandit.com/1993-honda-st1100-st1100/o/m151539#sch44203
I can live without the LF light for a while,but the rust will have to GO!
I can live without the LF light for a while,but the rust will have to GO!
ST1100Y
Site Supporter
For the ST the NTC isn't avail as individual spare part, only the whole pump assy... big $$$ though...
But many NTC units used in other models, like Varadero, etc... will technically fit, same specs and that, one only needs to desolder and remove it from the stem and install it as replacement on your ST1100 fuel pump bracket.
There a number of threads in this forum from folks who'd obtained an NTC with identical specs at RadioShack or similar vendor, to fix the item in their bikes.
However, the Varadero part would have costed me about 70,- whilst I got the whole pump for 54,- and saved time... just dropped the pump in and that's it, took about 20 minutes in the garage.
And yes, also I was surprised over having to find rust there... yikes... seems the dew from the rear wheel spray accumulates there... (probably also the reason why reusing the gasket didn't work)
I cleaned and gently sanded the rim (it was only corroded at the last 2~3mm of the "lip") while placing a rag underneath to prevent debris contaminating the fuel and treated the metal a film of ACF-50, should do for another decade.
But many NTC units used in other models, like Varadero, etc... will technically fit, same specs and that, one only needs to desolder and remove it from the stem and install it as replacement on your ST1100 fuel pump bracket.
There a number of threads in this forum from folks who'd obtained an NTC with identical specs at RadioShack or similar vendor, to fix the item in their bikes.
However, the Varadero part would have costed me about 70,- whilst I got the whole pump for 54,- and saved time... just dropped the pump in and that's it, took about 20 minutes in the garage.
And yes, also I was surprised over having to find rust there... yikes... seems the dew from the rear wheel spray accumulates there... (probably also the reason why reusing the gasket didn't work)
I cleaned and gently sanded the rim (it was only corroded at the last 2~3mm of the "lip") while placing a rag underneath to prevent debris contaminating the fuel and treated the metal a film of ACF-50, should do for another decade.
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If the idiot light NTC has to be submerged you would think it would be on the fuel sensor so it would be submerged until the level gets low as the fuel pump sits at the top of the tank.Odd,...
Gaskets ordered top and side in case I pull the sensor,...
Gaskets ordered top and side in case I pull the sensor,...
ST1100Y
Site Supporter
Na, the fuel sensor (basically a wound resistor) sits at half height of the tank (LHS) and hinges a long steel-rod with a float at the other end, actuating the sliding contact at he resistor... varying voltage moves the needle of the gauge (technically just a voltmeter).
The fuel warning NTC has to sit way lower, like the bottom 1/8th of the tank, and since the fuel pump rests at the bottom, they simply stuck the NTC to the bracket.
Found a nice pic at Mike Martin's page:
The fuel warning NTC has to sit way lower, like the bottom 1/8th of the tank, and since the fuel pump rests at the bottom, they simply stuck the NTC to the bracket.
Found a nice pic at Mike Martin's page:
John OoSTerhuis
Life Is Good!
The excellent pictures and schematic have been restored to the AOW article:I'm not sure, and I'm not near the garage and service manual.
Just noticed Carroll's pictures and Tom's schematic are missing from the AOW. I can contact my friend Tom about that if anyone's interested. There's a LOT of broken links after Webshots changed to Smile.
http://www.st-riders.net/index.php?topic=976.msg6775;topicseen#msg6775
Thanks, Tom!
John
Trying to figure out how to remove the fuel sensor assembly but no reference in the shop manual.Clymer says "release the retainer" which looks like a large lock washer,just can't figure out how to free it.
Anybody know?
Anybody know?
ST1100Y
Site Supporter
LOL! ;-)
I'd replace the gasket and give the new one slight smear with silicone-grease upon assembly... will ease things now and in the future.
Already on hand.
Found a fair amount of rust around the filler area.Just light surface rust,so and good cleaning with cider vinegar and some nuts and bolts and then a coating of Kreem liner should get me right!