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Discussion Starter · #1 ·
So now I've bought 2 new fuel sensors from Ducati. Neither one seems to work. I know they are notoriously inaccurate, but shouldn't new ones work? My low fuel light is always on. With a full tank of gas, if I disconnect the plug to the fuel sensor/fuel pump, my multimeter shows a closed circuit at the fuel sensor (yes, I know which wires to check), which would make the dash light turn on as if the tank were low. Therefore, I'm only checking the fuel sensor since nothing else is connected in the circuit. Am I crazy? Missing something? I even got a phone call from Ducati in Italy in response to my email about Ducati Seattle not being willing to replace the new, non-functional sensor I bought from them. Of course Ducati says "Tough shit. No returns on electrical parts" (I'm paraphrasing). Any ideas, or have I really spent $250 for 2 faulty, brand new fuel sensors? I could take the bike to a dealer and have them do what amounts to an easy, 1 hour job, but it's more than 700 miles round trip to the nearest dealer (Salt Lake Motorsports).
Anyone want to buy a new fuel sensor (cheap) that works great for the fuel pump only :eek:?
 

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Hi Joe,

Pretty sure, if my memory serves me correct, I posted some info on checking resistances etc. Maybe I just thought about it and did not do it. Quite likely:)

Maybe post this latest post into your original thread so we can see the history of what you have done and what was suggested.

That way I will see what, if anything, I posted. I know I at least thought about writing stuff on testing resistances with the sensor in and out of the wiring and even draining and refilling the tank.

Dunno - so please resurrect the original thread.

Richard
 

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Discussion Starter · #3 ·
http://www.ducati.ms/forums/57-supersport/134974-help-needed-fuel-level-light.html
Thanks for the idea Punch. Here's the old thread. No help, unfortunately. I have a good wiring diagram, which doesn't help either. I have checked resistance with my multimeter until I am blue in the face (is that an expression?). The dash light is always on when connected to either of the new sensors, whether the tank is full or empty. The light goes out when the sensors are disconnected at the tank plug. Both sensors read a closed circuit when held upright or upside down. When either sensor is in the tank full of gas, the multimeter reads a closed circuit, at the plug under the tank. 2 bad sensors?
 

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http://www.ducati.ms/forums/57-supersport/134974-help-needed-fuel-level-light.html
Thanks for the idea Punch. Here's the old thread. No help, unfortunately. I have a good wiring diagram, which doesn't help either. I have checked resistance with my multimeter until I am blue in the face (is that an expression?). The dash light is always on when connected to either of the new sensors, whether the tank is full or empty. The light goes out when the sensors are disconnected at the tank plug. Both sensors read a closed circuit when held upright or upside down. When either sensor is in the tank full of gas, the multimeter reads a closed circuit, at the plug under the tank. 2 bad sensors?
Blue in the face or F^ck what is going on! Logic and reality don't always match.

Not that I doubt you, but if you have tested both sensors upright and inverted and they both read zero resistance, not connected at all to the bike's harness, then both are stuffed!

I know this is really obvious but if you test their resistance not in the tank/ not connected to anything else, then normal way up should be zero resistance and upside down (like a full tank) should be infinite resistance.

Richard
 

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Discussion Starter · #5 ·
Actiually, the resistance is infinite no matter whether they are rightside up or upside down, also when they are in the tank full of gas. This shows a closed circuit, which would make the low fuel light turn on. I appreciate your help Punch; you seem to understand electrical issues.

Now, Shazaam, I could use your 2 cents worth.
 

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Joe - you began your original thread by saying you replaced the fuel sender unit in your SS. Now you are saying you've tried two new fuel level sensors and neither work. Now, i'm not familiar with this area of bike electrics, but i assume you replaced the sensors separately from the sender unit. If so, then Logically it would be more likely that the sender unit is faulty (or not correctly fitted) than getting two new sensors that were both bad. In the original thread you seemed resigned to re-doing the fuel sender repair. Did you take it out, examine it, and re-do the job? What was the source of the sender? New? Used off eBay?

Just saying it is very unlikely you have received two bad sensors from Ducati; something else HAS to be he issue. You need to backtrack and recheck your work at every step. Possibly invite a handy local friend over to sense-check as you go. Failing that, a 700 mile trip to the dealers will start to seem cheap :eek:
 

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Discussion Starter · #7 ·
Sender=sensor

In my original post I was incorrectly calling the part a "fuel sender." When I ordered it, I discovered it is correctly called a "fuel sensor." One and the same. I'll be in S.L.C. on Labor Day for a track day at Miller, so I may just leave this bike there the next day. It seems unreasonable to me too that 2 new ones would be bad, but it sure seems to be the case. Both where bought new from Ducati dealers.
 

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Actiually, the resistance is infinite no matter whether they are rightside up or upside down, also when they are in the tank full of gas. This shows a closed circuit, which would make the low fuel light turn on. I appreciate your help Punch; you seem to understand electrical issues.

Now, Shazaam, I could use your 2 cents worth.
I went back to look at the original thread and what you write above compared to the original thread is odd.

Originally you wrote that the light is on all the time.
You also wrote that with the sensor disconnected you could make the light go on by connecting the harness wires together or go off by disconnecting the harness wires. All good stuff as it means the harness side of things is OK.

I.e. when the fuel is low, the sensor resistance is very low. When the fuel is high, the resistance should be infinite. In this case the meter should display OL.

Above you have written that the resistance is infinite and also that shows a closed circuit. If it is infinite, then the circuit is open and current cannot flow to the light. Maybe the "infinite" was a typo due to your frustration:D

Has the light been on ever since you bought the bike?

Clutching at straws ....
How many wires go into the connector?
If 4, then 2 for the fuel pump and 2 for the sensor so the resistance test should be a no brainer.
If 5, then maybe the sensor has 3 wires to give an option of closed or open when the sensor is low or the opposite when high.

Maybe a previous owner put on a new harness connector to suit a different sensor/fuel pump wiring and wired it incorrectly.

Maybe you do have two faulty sensors. I have read this has happened to others.
Does anyone else have a sensor lying around to check resistances between terminals?

Bummer you don't live nearby in Oz!

Electrics - former 25 years in the solar electric industry had me designing electronics, playing with batteries etc. Also did some electronics study at Uni in the dim distant past. I work in the energy efficiency field now and frig with my and mates bikes, so still keep in touch.

Richard
 

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Discussion Starter · #9 ·
I'm ignorant!

Sorry, Punch. I (think) I know how to use a multimeter, but I got my terms screwed up (again). The sensors always show a closed circuit, which I guess means "zero resistance," not "infinite resistance." :eek: There are 4 wires, 2 to the fuel pump and 2 to the sensor. I'm checking the correct ones, I'm sure of that. My multimeter always shows a complete circuit (zero resistance?) when I check them. The wires are all the correct colors, according to the wiring diagram. The low fuel light, when hooked up to the sensor, has always been on, and immediately goes off when I disconnect the sensor, ever since I bought the bike. Thanks for all your help. I sent the second sensor back to Salt Lake Motorsports and they are going to check it out. Hopefully they will find out it's bad and send me a good one... We'll see.
 
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