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Thread: 4ag wiring issue, power to ecu but no power out??

  1. #1
    Forum Member 1st year Apprentice SLO-055's Avatar
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    Default 4ag wiring issue, power to ecu but no power out??

    hey all
    i've got a very annoying problem, i've wired in my bigport 4ag to my ae86 as per how i've read in write ups and using a few wiring diagrams, all seems well, i've got power to the ecu from my two ign sources an one battery source, the ecu sees power fine, the issue is it isn't putting anything out, from my guess i should see some power at the distributor (a power, earth and signal wire would be the three coming out right??) but i've got nothing, iv'e got power to injectors but no pulse when cranking.
    i've wired in some a/m management systems before bit this is my first attempt at the standard ecu
    soo here i sit in hope that someone will post back saying 'hey flog bag, you haven't....' and it'll be a simple fix and all good, woot and all that.
    btw, i've tried another bigport ecu, another coil and ignitor, another distributor, but obviously my problem lies with my wiring somewhere...
    thanks again for your time, it's greatly apprecitated!!!!
    ed
    insert witty post here, to allow people to see how funny and intelligent i am, and how much they would like to be like me.

  2. #2
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    ECU shouldn't give much power out? except maybe for TPS?

    the ECU grounds the injectors.

    it receives a voltage/signal from the O2, the AFM/MAP, but it should send out voltage to the temp sensors. (and maybe 5V to the AFM/MAP?)

    for dizzy, the power comes from the ignitor? and ECU only receives a pulse or grounds ignitor to fire? or does it send pulse to ignitor?

    anyway, check the temp sensor power out first? then MAP?
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  3. #3
    Mad****** Grease Monkey FASTFOO's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    OK
    The 3 powers you reffer to are +b,+b1 (have power from the efi main rely only with ignition on) and "batt" that is power all the time (like a radio memory) and thats ok.

    The only "real" power out of the ecu when powered up should be 5v from "vc" that runs to your tps and map sensor.

    The dizzy should never see power. The 3 wires are "ne"(crank shaft rpm) "g" (cam reffrance) and "g-" (the other side to both pick ups) and the only power in these wires is made by the pick ups in the dizzy and is usaly less than 0.5 v

    As far as injectors go they should have power whenever "+b" has power and should come from efi main. To fire the injectors the computer earths them out by joining "#10" and "#20" (from injectors) to "eo1" and "eo2" (they earth back to the engine) Have you got eo1,eo2 and e1 all going to a good earth?

    I Was going to type more but have to go!

    MATT.

  4. #4
    Junior Member 1st year Apprentice Fred_SPb's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    Try to connect "Chek engine" lamp (W pin). Next read error blinking codes. Injector pulse generates by ECU if the ECU recieve signal fron camshaft sensors. No signal - no pulse.

  5. #5
    Raastler Grease Monkey
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    What loom is it? What car is it ?

    Using an AE82/AE92 loom the Coil/ignitor and injectors use the same power seperated by a mini fue block on the loom. Give power to your Coil on the positive (+) which will transfer into the ignitor, down the loom into the Injector pinout and injectors there for givign you an almight fuel and spark.

    Hope this helps.

  6. #6
    Frontyarding Grease Monkey Mitchee's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    I had this same problem when I swapped the engine over in my AE82, I missed an earth thats amongst the injectors that bolts to the inlet manifold. Have a look around there.
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  7. #7
    Forum Member 1st year Apprentice SLO-055's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    thanks for all your help guys, i really really appreciate it!! still no go tho, earths that go on inlet are sorted, powered coil positive, have power at injectors, still no spark, tried another coil an ignitor, still no love.
    connected check engine light, nothing
    loom is ae82, car is ae86.
    no spark but power to squirters surely means i've got an issue from the distributor side??anyone got any sidedraught webers for sale??? joking.
    insert witty post here, to allow people to see how funny and intelligent i am, and how much they would like to be like me.

  8. #8
    Mad****** Grease Monkey FASTFOO's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    Check your timing belt!!
    Sounds crazy but i have been cought out on it before.
    MATT.

  9. #9
    Forum Member 1st year Apprentice SLO-055's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    checked that, it's all good there
    checked ecu power out, is just as old corollas said it should be.
    anyone selling webers??
    insert witty post here, to allow people to see how funny and intelligent i am, and how much they would like to be like me.

  10. #10
    Junior Member Grease Monkey 78Rolla's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    Tough it out SLO-055!!! I had heaps of wiring troubles when i was fitting the 4age into my KE30...check to see the wires haven't broken somewhere - maybe get a multimeter and test for continuity? just to rule out a broken connection. Also - are you getting fuel to the engine? maybe your pumps playing up and causing dramas (just that i thought i had a wiring problem, but it was a faulty high pressure pump)...good luck!

  11. #11
    Junior Member 1st year Apprentice Fred_SPb's Avatar
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    Default Re: 4ag wiring issue, power to ecu but no power out??

    Connect all wires. Turn ignition on and check +12 V on all points.
    1. Ignition coil
    2. Fuel injectors
    3. Ignitier
    4. MAP
    5. Temp sensors
    Temp sensor are not critical for starting the engine, but for example - without signal from MAF sensor silvertop's ECU don't control injectors and ignition - fail safe mode... maybe

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