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Fuel Sender bad ohms good gauge

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Old 08-09-2012, 10:32 AM   #1
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Icon2 Fuel Sender bad ohms good gauge

We have a problem trying to connect a data acquisition system to read the fuel sender off a 92' Civic.

When we read the fuel sending unit (floater) at the connector, the ohms readings are all over the place. Sometimes it shows the right ohms other times it shows crazy ohms like 100K ohms. Needless to say the data acquisition system jumps everywhere. The sender still inside the tank, we have not remove it.

So I would tend to think that the fuel sender is bad, but when you install the regular original gas gauge of the car, the gauge shows the correct gas level. Further crazy, after you use the regular gas gauge the sender starts working showing the correct ohms for a while until the car is off again, or if you wait long enough.

Any ideas on what could be happening here? Anyone has seen this behavior before?

Thanks,
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Old 08-09-2012, 10:43 AM   #2
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Default Re: Fuel Sender bad ohms good gauge

Sounds like you are not making good contact with the connector terminal during your measurements.
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Old 08-09-2012, 06:50 PM   #3
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Default Re: Fuel Sender bad ohms good gauge

Thanks for looking into this [email protected] We took a closer look and actually cut the wires going into the sender so we had good access to the resistance measurement.

We are still not sure why we are not able to read the resistance from the sensor by itself while still in the tank. Nevertheless we are able to get the data acquisition to read the level of gas.

It seems as if there is a charging circuit that allows the circuit to work. I know there is nothing in there that would behave like that. We were seeing this with a tank pretty empty, once we added more gas into the tank, we got better readings.

Thanks for the help if you have other ideas I would love to hear them. It is my understanding that the fuel sender is just a regular potentiometer nothing else. Unless you get one of those fancy senders that measure the capacitance of the gas
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Old 08-09-2012, 06:58 PM   #4
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Default Re: Fuel Sender bad ohms good gauge

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Old 08-09-2012, 08:06 PM   #5
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Default Re: Fuel Sender bad ohms good gauge

The schematics for the 92' civic we have only shows the fuel sending straigth to ground. Where does the Empy Light signal go to?
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Old 08-09-2012, 08:09 PM   #6
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Default Re: Fuel Sender bad ohms good gauge

Quote:
Originally Posted by Diode View Post
The schematics for the 92' civic we have only shows the fuel sending straigth to ground. Where does the Empy Light signal go to?
You're right. I posted the diagram for 96-00 Civics, but 92-95 Civics are the same, except they lack the low fuel light part of the circuit.

Post your diagram.
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