Fuel Warning Light Stays On With Full Tank

So the deal is, today the fuel warning light comes on even with a full tank of gas. Here's some things that happened to me yesterday though I don't know if it's related.

I was riding for the first time in a while because the headlight fuse had popped (didn't want to ride without the fuse and I can't find the dang little things in this town. Since I was going to replace the fuse block anyway I let it slide for a few weeks and just didn't ride it. But I went for a quick spin yesterday regardless).
A mile away from my house, the bike loses power and quits. I find that the ignition fuse has gone, so I take the fuse from the signal slot and replace the ignition fuse with it. I notice that the fuse that had been in the ignition slot was 30 amps instead of 10. Crap.
so I ride home with no brake lights
Today I switched the fuseblock for a new blade type. Everything works great! But that fuel warning light will not go off.
How can I check to see if it is mechanical (sender) or electrical (atari computer)? Could the 30 amp fuse have fried part of it? Or could that be coincidence?
I don't suppose there is a reset button?
Bike is as in sig.

 

Have you checked the connection for the level sensor, its under the seat. Does the 750 have a level gague and light or just a light? Most likley its the sending unit giving problems.
Unplug it and check with a meter. Sensor for a light should read open when tank is empy and closed when full. Gague should read between 0 ohms for empty and around 300ohms when full ( my XJ1100 reads between 0 and 300, I'm not sure what the 750 will read but it should be close).
The main fuse blowing is probably a coincidence. They will blow if you have bad commections there which you already fixed.

 

My 750 has the digital gauge with a warning light, so it's the computerized version.
Which connection is it under the seat? I suppose it's the one that leads to the tank...

 

Ding ding ding, Yup... 3 pin connector that I regularly forget to plug in myself. Just to the right of the back of the tank.

 

I see it; it's connected. It looks like I may have caught it with the air filter cover when I replaced it though. Perhaps I've "pinched" it or something. I'll have to check it out tomorrow for sure; it's too dark tonight already

 

There is the possibility that today was "the day" that your float assembly stuck. Both of mine suffered with corrosion issues before I blasted them clean. You need to ohm out the sensor to determine if this is your problem since it wasn't unpugged.

 

Well, on my bike it is a 2 wire connector. It does seem to be the problem though. It intermittently shows ohms. If I jiggle the wires next to the sender, it will show and then not show. Bad/dirty sender maybe. I assume that since there are 2 wires in the loom that the sender does NOT ground on the tank.
I'll have to detach the sender and clean everything up I suppose.

 

Three pin connector with only two pins is normal.
Sounds like you might have a broken connection. Pull the sender and inspect. There was a great set of pictures on the forum here about a month ago showing cracked/broken connections on a member's sender. You might be joining the club this time around. Let us know what you find. You have a few options to repair it.

 

I think this might be the pic Robert was thinking about; this is a 550 Seca fuel gauge sending unit:



This particular unit was still functioning; the markings on the pic are to point out the the little lead wire and that all the insulation had crumbled off where it passes through the housing.

You can see the quality of the solder joint in question. If I recall, the other lead wiire is simply soldered to the outside of the sending unit.

A couple of things to keep in mind: Ohm readings full/empty vary from bike to bike; some are high resistance full, some high resistance empty; and the Ohm ranges are different too. If you're comparing readings, be sure to compare to the same bike.

 

Thanks Fitz, thats the one!

 

And let's not forget.....for some models, the factory doesn't give you the ohm specs (grrrr!)

 

So, it's winter and I've got time to mess with this. I pulled the sender unit from the tank to ohm it up (and yes, I realize NOW that I could have just disconnected the pig tail without removing the sender but, oh well, at least now I know how everything goes together).
It reads 35 to 300 or so. I assume that is within tolerance. So I guess I'll be putting it back into the tank tomorrow to see if it gives the same readings once it is hooked up. I am pessimistic that the sender is the problem though. What should be the 2nd thing I check? Is there another point where I can stick my ohm-o-matic to ensure that the wire does not have a break somewhere in the loom? I'm still mindful that I developed this problem right after I was futzing around with the wires, so maybe I just pulled on the wrong thing a bit too hard...?

 

I've decided that 300 ohms is teh empty; that's the only way it would fit in the tank.
Happily, It looks like that connector under the seat is the culprit.