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Thread: Rpm

  1. #11
    Constant Bitrate
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    Your car most likely has the fuel pump in the tank. Go to an auto parts website like Autozone and lookup your fuel sender. The specs on it will tell you the resistance range. You can do this for oil pressure, water temp, etc. You might even be able to find the number of pulses from your VSS.
    Thanks,

    Dan

  2. #12
    Variable Bitrate nemo1's Avatar
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    Found this wiring diagram for the Lexus LS400. Should I be tapping the resistor? If yes how should I do it? There probably will be a current flowing thru the resistor already. How could I do a voltage divider?


  3. #13
    Raw Wave
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    That's the fuel pump circuit - not fuel level.

  4. #14
    Variable Bitrate nemo1's Avatar
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    I've attached the doc of the circuit....I can't seem to find the sensor for fuel level. Only found fuel pressure on the upper right corner of the diagram. Anyone have any ideas what type of sensor a 91 Lexus LS400 uses? Should be resistive type but couldn't find it.

    Another question, I saw the fuel pressure sensor seems to be connected to a solenoid. Does this means it is returning variable frequency signal and not variable electrical signal? I'd need a frequency to voltage converter board right?

    Thanks
    Attached Images Attached Images

  5. #15
    Raw Wave
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    That's engine control stuff.

    You need the gauge wiring (dash console etc).
    That's assuming you want the fuel (tank) level?


    For engine speed there is the engine speed sensor, left or right dizzy, ignitor, sensor etc.

  6. #16
    Variable Bitrate nemo1's Avatar
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    Yes I need the fuel (tank level).

  7. #17
    Raw Wave
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    Just to allay some concerns. (Yes - "The Man" is concerned - probably just like others including myself.)

    With regard to the fuel sender....

    FORGET EVERYTHING to do with the diagram you have posted etc.
    The resistor is to reduce fuel pump current at certain times.
    The fuel pressure switch is a safety etc sensor.
    18k sounds VERY wrong for a fuel sender.


    Chances are your fuel sender will be from near 0R (zero Ohms) empty to around 100R full. (For Lexus I have read ranges like (roughly) from 0R to 5R, 0-72R, 0-140R.)

    Your sender voltage may vary if the fuel gauge has a bi-metal voltage regulator. These pulse on/off to provide an average voltage (usually ~8V).
    If so, you need to integrate the signal (ie, an RC filter, I wouldn't use FB or uPC etc averaging). Maybe a 3-10 second filter is sufficient. Else use an analog regulator.
    (If you disconnect the sender, no filtering (other than noise) is required; eg - use it with a 47R resistor.)


    Stay away from anything on that diagram that you posted. (Except for the ignition/RPM signals).
    That diagram has NOTHING to do with the fuel gauge.
    So too the replies if referring to that diagram... (including resistance changes with engine running or not).

    With thanks to "The Man"... (u know who you are)

  8. #18
    Constant Bitrate
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    Looking at Autozone's website, it appears that the fuel level sender reads 240ohm empty and 33ohm full.
    Thanks,

    Dan

  9. #19
    Variable Bitrate nemo1's Avatar
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    Quote Originally Posted by OldSpark View Post
    Stay away from anything on that diagram that you posted. (Except for the ignition/RPM signals).
    That diagram has NOTHING to do with the fuel gauge.
    So too the replies if referring to that diagram... (including resistance changes with engine running or not).

    With thanks to "The Man"... (u know who you are)
    Where can I get the signal that you mentioned from?

  10. #20
    Raw Wave
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    From the fuel gauge. EG - the fuel tank sender or the dash.

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