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Thread: what is this relay 4

  1. #1
    Forum Member 1st year Apprentice
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    Default what is this relay 4

    i have a ae82 corolla 16valve
    4age,
    and on the side of the e.c.u there is some sort of relay circuit.Does any body no what it is for ...........

  2. #2
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    Default Re: what is this relay 4

    fuel cut relay and im pretty sure it also does the preprime. been a long time since i played with a standard rolla puter

  3. #3
    Junior Member Grease Monkey
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    Default Re: what is this relay 4

    it would be whats knows as an opening curcuit relay. Used to control the fuel pump on toyotas

  4. #4
    Junior Member Automotive Encyclopaedia
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    Default Re: what is this relay 4

    toyotas dont seem to do a pre prime, I think it would be good if you could find a circiut opening relay that did do it, good to have fuel pressure before starting .

  5. #5
    Junior Member Grease Monkey
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    Default Re: what is this relay 4

    Quote Originally Posted by cambelt1
    toyotas dont seem to do a pre prime, I think it would be good if you could find a circiut opening relay that did do it, good to have fuel pressure before starting .
    Preprime on them is not worth worring about, they all start perfectly fine from the factory

  6. #6
    Junior Member Grease Monkey toyoda's Avatar
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    Default Re: what is this relay 4

    Its a circuit opening relay.

    Its a relay with two coils in it - one operated by the Ignition key in the Crank position and one by the ecu when it gets a speed signal from the Distributor.

    Ensures that if the engine stops - the fuel pump stops.

    Toyoda

  7. #7
    Junior Member Domestic Engineer RobertoX's Avatar
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    Default Re: what is this relay 4

    ^^ or on cars with air flow meters the second coil is wired to a switch in the air flow meter, if there is no air going through it (ie engine is dead) the relay will open. (according to the 4AGE manual on the old forums)

    it is there for safety reasons, if you should be in a crash and a fuel line is severed so the engine stops but ignition is still on, you dont want the fuel pump to merrily feed fuel to what could possibly be the burning remains of you and your car

  8. #8
    JZ Powered Too Much Toyota EldarO's Avatar
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    Default Re: what is this relay 4

    Quote Originally Posted by bansheebuzz
    Preprime on them is not worth worring about, they all start perfectly fine from the factory
    mine doesnt, always needs two cranks to get it started if it hasnt been driven in a while.

    Eldar.O.

  9. #9
    Toymods V8 Member Too Much Toyota CrUZida's Avatar
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    Default Re: what is this relay 4

    I'd say your CSI isn't operating properly
    Peewee
    1985 MZ12 Soarer - 1UZ Powered
    2013 86 GTS

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    Default Re: what is this relay 4

    Quote Originally Posted by bansheebuzz
    Preprime on them is not worth worring about, they all start perfectly fine from the factory
    lol because of the preprime!

  11. #11
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    Default Re: what is this relay 4

    Quote Originally Posted by cambelt1
    toyotas dont seem to do a pre prime, I think it would be good if you could find a circiut opening relay that did do it, good to have fuel pressure before starting .
    i think you will find all efi toyota's preprime

  12. #12
    Toymods V8 Member Too Much Toyota CrUZida's Avatar
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    Default Re: what is this relay 4

    I think you'll find no Toyota's preprime.

    None of mine ever have.

    Every one I've seen, the fuel pump is triggered by the START key, and then either by the flap AFM registering air, or by the ECU registering RPM.
    Peewee
    1985 MZ12 Soarer - 1UZ Powered
    2013 86 GTS

  13. #13
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    Default Re: what is this relay 4

    Quote Originally Posted by CrUZida
    I think you'll find no Toyota's preprime.

    None of mine ever have.

    Every one I've seen, the fuel pump is triggered by the START key, and then either by the flap AFM registering air, or by the ECU registering RPM.
    maybe its just the airflow ones! but i know the map ones do or at the very least the 4ag small ports do.

  14. #14
    Fava beans and chianti Backyard Mechanic AE86slut's Avatar
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    Default Re: what is this relay 4

    Quote Originally Posted by kingmick
    4ag small ports do.
    All 4As I've ever dealt with do. 4AGE 16V, 4AGE 20V, 4AGZE, 4AFE. Interesting.
    I am not a doctor, or a mechanic...
    A.K.A Otomoto
    All new - Fart!
    Quote Originally Posted by Vios-GT_07
    it was 10,000 kms b4 it saw the red-line.. but even then i seldom push it that hard unless i have to prove a point i.e. competition

  15. #15
    Toymods V8 Member Too Much Toyota CrUZida's Avatar
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    Default Re: what is this relay 4

    Must be a 4A thing then!

    None of the JZ's, M's, G's or UZ's I've worked on do.
    Peewee
    1985 MZ12 Soarer - 1UZ Powered
    2013 86 GTS

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