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On two of our planes we have had the fuel PSI suddenly drop.  Based on the other forums I have read on here, it seems like the sender.  However I have gone through the Czech Sport Cruiser manual and can not seem to find anything in regards to a fuel sender or fuel sensor.  So my question is:  What is the difference between a fuel sender and a fuel sensor?  I imagine this is the fuel sensor and that both planes have a bad one.  

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  • Re: Fuel Sender vs Fuel Sensor

    by » 6 weeks ago


     

    The terms 'sensor' and 'sender' are used interchangeably. It is used to describe the part that converts the physical parameter into an electrical signal. i.e. temperature to resistance or pressure to resistance.

     

    Pressure sensors are generally resistive or capacitive and often incorporate a circuit to produce a voltage proportional to the pressure. This can then be fed to the gauge/EMS. The voltage based senders have 3 wires, a supply, a ground and the signal wire. Often they require a regulated 5V DC supply. It is always worth checking the ground continuity and supply stability. You could then monitor the output signal and see if it changes with pressure changes. That will allow you to determine where the fault lies.


  • Re: Fuel Sender vs Fuel Sensor

    by » 6 weeks ago


    Thank you Kevin.  I'm still a newbie when it comes to using a multimeter to diagnosis electrical gremlins.  If its not too much to ask, would you mind explaining what I should do.  I did unplug the sensor and saw the three female cavities for ground, power and signal.  Just not sure how to test the ground continuity.


  • Re: Fuel Sender vs Fuel Sensor

    by » 6 weeks ago


    Your best bet is to watch some youtube videos about checking resistance and measuring voltage using a multimeter. There will be plenty of automotive videos that will cover what you need to know. This is what you will need to do:

    1. Disconnect the plug from the pressure sensor.

    2. Set your multimeter to ohms. Connect the black probe to a good ground like the inlet manifold or crankcase. You can usually clip the probe on the ground tag of a wire that you can see bolted to the metalwork. The ground braid to the ignition modules is also another good point to use.

    3. Touch the other probe to each of the terminals in the pressure sensor harness. One of them should measure less than 1 ohm. That is the ground connection. Be careful not to push the probe right into the terminals otherwise you will make them loose.

    4. Set your multimeter to DC volts. With the master switch on, touch the red probe to the other 2 terminals. One of them should measure 5V. Check that it is stable and not varying by more than 0.1V. That terminal is the supply to the sensor.

    5. Plug the connector back onto the sensor. You will now have to back-probe the 3rd terminal. You may have to poke a thin piece of solid wire (something like thin lock wire) through the back of the plug housing to make contact.

    6. Measure the voltage with the master switch on. Now switch on the electric fuel pump to increase the fuel pressure and see if the voltage increases.

    7. If the voltage doesn't increase, just double check the supply terminal with the plug connected just in case the sensor is pulling the voltage down. If it is not then it is likely that the sensor is either blocked or faulty.

    I hope that helps.


    Thank you said by: RotaxOwner Admin

  • Re: Fuel Sender vs Fuel Sensor

    by » 6 weeks ago


    Thank you thank you thank you Kevin!  That definitely helped and the explanation was straight forward and easy to understand. 


  • Re: Fuel Sender vs Fuel Sensor

    by » 6 weeks ago


    When you say "the fuel PSI suddenly drops", are you saying you get zero indication or it drops below the minimum fuel pressure? I want to make sure you are not actually losing fuel pressure VS an indication error?

    Also, is there an engine RPM related to the fuel pressure drop? For example, as soon as the engine reaches 5200 RPM the fuel pressure fluctuates and drops below the minimum 2.2 PSI.

    Does turning on the boost pump make any difference regarding the pressure indication? 


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