328 - when does the fuel pmp start? | FerrariChat
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328 - when does the fuel pmp start?

Discussion in 'Technical Q&A' started by Iain, Nov 9, 2008.

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  1. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,351
    UK
    #1 Iain, Nov 9, 2008
    I have had replacement hoses made for the two steel braided lines that are the flow & return to the KJet (under the airbox). When I fit these obviously I need to make sure they are properly sealed so can anyone tell me when the fuel pump actually starts? Is it when the ignition is switched on or does the motor actually have to be cranking? i.e. is just switching the ignition on enough to test them or do I need to start the car?

    I have many of the vacuum hoses removed at the moment so I can't actually start it unless i put them back on (and I'm trying to get replacements).
     
  2. fastradio

    fastradio F1 Rookie
    BANNED Professional Ferrari Technician

    Apr 26, 2006
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    David Feinberg
    #2 fastradio, Nov 9, 2008
    Iain,

    The easiest way to run the pump, so that you can test for fuel system integrity is:

    -Ignition key in "ON" position
    -Unplug the "Blue" connector on the Fuel Distributor housing (This is the fuel pump safety switch)

    The fuel pump will now run. If you need to stop the pump, quickly, whilst you're still in the engine compartment, simply plug back in the Blue connector.

    David
     
  3. Iain

    Iain F1 Rookie

    Jan 21, 2005
    3,351
    UK
    #3 Iain, Nov 9, 2008
    Last edited: Nov 9, 2008
    Thanks very much, I'll give that a go.

    Edit to add: yep , that works! As a matter of interest does that also start the thing spraying fuel out the injectors? I didn't run it for more than a few seconds & you can tell that there is a lot of fuel moving through there when its running.

    All seems to be dry :)

    For anyone interested (in the UK) I got these pipes made up for me by Pirtek. These are NLA from Ferrari.
     
  4. fastradio

    fastradio F1 Rookie
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    David Feinberg
    #4 fastradio, Nov 9, 2008
    If the fuel distributor sensor plate is "at its rest position", the injectors won't "fire". However, if the sensor plate is depressed, they will fire. Also, if you have a "leaky" injector, fuel will be sprayed by that injector into the combustion chamber.
     
  5. DGS

    DGS Seven Time F1 World Champ
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    DGS
    #5 DGS, Nov 9, 2008
    Last edited: Nov 9, 2008
    The long answer is that the fuel pump safety switch is linked to the airflow plate. The fuel pump will only run with the ignition switch on *AND* (a) when cranking the engine (key switch in "start" (avv)), or (b) when the engine is sucking air. If the engine stalls, the fuel pump is shut off. (That blue connector unplugs the airflow plate "safety switch", causing the fuel pump relays to think the plate is not at rest.)

    When the pump is running, fuel is delivered to the fuel distributor. The CIS (continuous injection system) is theoretically always running the injectors when the fuel pump is running. The airflow plate deflection mechanically regulates pressure to the injectors. CIS injectors have an internal valve that shut off fuel delivery below a given pressure.

    Of course, with 20 year old injectors, they might not shut off completely, so if you have the original steel injectors, you might be leaking fuel into the intake manifold when the pump is running. But if everything works right, you won't get fuel delivery until the engine is pulling air past the airflow plate.
     

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