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Is there a difference between a car fuel pump and a water pump

  1. Apr 13, 2012 #1
    I am going crazy!

    These websites appear to contradict one another...

    The lowering of the diaphragm makes the inlet valve of the fuel pump open. With this valve open, fuel is drawn from the gas tank and into the pump. At the same time, the lowering of the diaphragm closes an outlet valve.

    Read more: How Car Fuel Pumps Work | eHow.com http://www.ehow.com/how-does_5004513_how-car-fuel-pumps-work.html#ixzz1rwSrcgdV

    A vacuum is created inside the pump casing each time the diaphragm is raised (see figure below). This opens the inlet valve and seals the discharge valve allowing water and air to enter the pump. When the diaphragm is lowered the resulting pressure seals the inlet and opens the outlet valve purging the pump housing of water and air..


    So which way round is it? When the diaphragm is raised does this open the inlet and close the outlet or the reverse or do these pumps work differently?
  2. jcsd
  3. Apr 13, 2012 #2


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    Gold Member

    Would you consider the orientation of the diaphram pump to be the reason for your confusion - do a flip of 180 degrees of one pump described and it acts exactly just as the other. What would the text say if the diaphram pump was operated in a 'sideways' orientation?
  4. Apr 15, 2012 #3
    Thanks. The other question is if the check valve jams and stays closed why is it less force will be required to move the piston down?
  5. Oct 16, 2013 #4
    Automotive fuel pumps are typically of the positive displacement pump family type. The PD pump design type is often typically a gear pump (for diesel app's) a piston pump or a diaphragm pump type for gasoline (petrol). These pumps are often powered by a DC motor, an induction coil or directly connected to the engine.
    Automotive engine water coolant pumps, almost universally are of the centrifugal pump design type.
    These pumps are typically driven by a belt drive off the engine or less often gear driven by directly being coupled to the engine.
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