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2001 CBR F4i reserve sensor problem

  #1  
Old 10-03-2010, 06:44 PM
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Default 2001 CBR F4i reserve sensor problem

Hi to everyone . . . I know that you have heard the same problem by many guys about the reserve fuel gauge but i think that my cbr has a little different one . . .

Actually, when i turn the key the little reserve bars appear for seconds and disappear when the cluster test ends . . . (i know that this is not a fuel gauge) "BUT" ( a reserve fuel gauge) . . . The problem is the following . . . wanted to test when the reserve bars would come up so i took it for a ride . . . i knew that my fuel was low since i have checked the tank with a torch (silly huh???) . . .

So when i started, i drove for about 20 miles and then the engine stopped ! (my fuel tank was empty and the fuel reserve gauge never light up!!) could someone tell me how on earth can i fix this thing?? i ve checked the 3 pin connector which connects the fuel pump as the service manual says but nothing happened. . .

could there be a problem in the fuel pump???
if so can it be fixxed without changing the fuel pump (by modifying any sensors or something???
 
  #2  
Old 08-06-2015, 12:03 PM
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Brining this thread back to life

I recently have the same problem. Reserve light came on as it should once reserve status is seen. Then reserve bars went out and never came on. I ran all the fuel out and the reserve lights never came on. Anyone have experience with this? Hopefully I can replace just a sensor of the fuel pump assy rather than shell out $400 for a new pump ask that I don't really need
 
  #3  
Old 08-07-2015, 06:12 PM
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Hello friend. After some years from when i posted this thread i found what the problem is.

FuelPump.jpg Photo by gc8_impreza | Photobucket

this is a picture of the fuel pump. As you can see between the fuel filter and the fuel pump, there is a silver rounded tiny box, with a brown cable on it.

this is the sensor that causes this malfunction.

It is called a thermistor.

Actually it is an NTC thermistor.

That means that when the fuel amount drops, that thing gets exposed and the resistance (counting on electronics theory) drops. When it drops below 150 ohms, the RES indication with the fuel bars, lights on. Then it counts up to about 25 miles, till the Reservoir bars stop staying lighted on, continiously.

Now in order to fix this you have 3 options:

1. change the fuel pump assembly (not advised if i were you)
2. change the thermistor sensor (this requires knowledge of basic electronics, but it is a cheap method)
3. Make a patent with a floating material that does not deteriorate on gasoline(like the ones that cars use to measure the fuel tank)

If you watch the sensor on the picture above, there is a brown cable. The thermistor, makes circuit on the rounded case, to the braket that keeps the rounded case on place.

I did the 3rd method. There is a simple diagram that i made to see how it works.



i simply emptied the rounded case, opened the bracket so that the rounded case, can be able to move easily up and down, attached a floating material that is resistand to gasoline, and on the bottom that there is the brown cable, i mounted an 150 ohms or less resistor , with an end that is able to fit in the rounded thermistor case.

one problem that you will come up to, is that the RES indication will light up sooner than previously, but you can adjust the floating material to be close to the botton in order to make it light earlier.

Mine opens at aproximately 6 to 7 liters before the gas tank gets empty.



I hope i helped you in a way.
 

Last edited by Dg_Ironman; 08-10-2015 at 02:38 PM. Reason: Image not attached correctly
  #4  
Old 08-10-2015, 05:35 PM
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Kick ***, thanks for sharing the solution!

Originally Posted by Dg_Ironman View Post
Hello friend. After some years from when i posted this thread i found what the problem is.

FuelPump.jpg Photo by gc8_impreza | Photobucket

this is a picture of the fuel pump. As you can see between the fuel filter and the fuel pump, there is a silver rounded tiny box, with a brown cable on it.

this is the sensor that causes this malfunction.

It is called a thermistor.

Actually it is an NTC thermistor.

That means that when the fuel amount drops, that thing gets exposed and the resistance (counting on electronics theory) drops. When it drops below 150 ohms, the RES indication with the fuel bars, lights on. Then it counts up to about 25 miles, till the Reservoir bars stop staying lighted on, continiously.

Now in order to fix this you have 3 options:

1. change the fuel pump assembly (not advised if i were you)
2. change the thermistor sensor (this requires knowledge of basic electronics, but it is a cheap method)
3. Make a patent with a floating material that does not deteriorate on gasoline(like the ones that cars use to measure the fuel tank)

If you watch the sensor on the picture above, there is a brown cable. The thermistor, makes circuit on the rounded case, to the braket that keeps the rounded case on place.

I did the 3rd method. There is a simple diagram that i made to see how it works.



i simply emptied the rounded case, opened the bracket so that the rounded case, can be able to move easily up and down, attached a floating material that is resistand to gasoline, and on the bottom that there is the brown cable, i mounted an 150 ohms or less resistor , with an end that is able to fit in the rounded thermistor case.

one problem that you will come up to, is that the RES indication will light up sooner than previously, but you can adjust the floating material to be close to the botton in order to make it light earlier.

Mine opens at aproximately 6 to 7 liters before the gas tank gets empty.



I hope i helped you in a way.
 
  #5  
Old 08-10-2015, 08:55 PM
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Dg_Ironman,
Thanks so much for your info. I see exactly the sensor. I learned a bit how it works which is a plus. I have a friend who is an electrical genius and he claims he can replace the thermistor. Part cost $1.50. So cheap! Looks like winter time project. Also according to my friend, these thermistors aren't likely to go bad. I'd believe it too since there is no information out there on the web or shop manual. Thanks again for the detailed info!
 
  #6  
Old 08-11-2015, 04:35 PM
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No problem. I am Glad that i could help you
 
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