1977 Fuel Injection help

Discussion in 'Big Block Cadillacs' started by Fleetwood, Sep 9, 2019.

  1. Fleetwood

    Fleetwood New Member

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    Recently acquired 1977 Eldorado with factory fuel injection, and trying to get it to start.
    Car cranks, I get spark, and in-tank fuel pump is running with ignition in RUN position. But the inline fuel pump doesn't run, and I get no fuel to injector rail.
    Are inline and in-tank fuel pumps both controlled by the ECU? Is spark/distributor controlled by ECU?
    Just trying to get some ideas, i'm suspecting a bad ECU/fuel pump relay, but the car is parked in the grass, and have yet to get under the car to test the fuel pump by supplying 12v to it directly.
     
  2. kzhurley

    kzhurley Active Member SUPPORTING MEMBER

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    I dont know anything about that efi, but I have the factory service manual supplements that you'd be welcome to for postage.
     
  3. DaveM

    DaveM Member

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    I know of only one expert on these systems, and that is Bruce Roe. He has a few mods that can help these systems live. But if were me, I would take the frame rail pump out and plum it straight threw. Then pull out that low pressure pump in the tank and put a high pressure pump in .And one of Bruce's mods is not to run the pump by the ECM , but just have the ECM run a relay with a new power line with a strong relay. Talking to Bruce could help you out a lot and he can repair your ECM.
     
  4. Caddylackn

    Caddylackn Member

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    I would think the inline fuel pump relay would be triggered by the ignition switch, and not the ECU, but I do not know cadillac EFI. If the car has been sitting I would carefully clean check the connectors to the ECU, sensors, and relays, check wires for mice chewing, and clean all the grounds you can find. And of course check the inline pump and relay.

    There is also the chance the fuel rail is plugged with old jelled fuel and maybe the inline fuel pump can't pump cause it has no where for the fuel to go (assuming no fuel return line or plugged rail before fuel return line) and pops the fuel relay, or the inline pump is just bad.
    If you open up the fuel line at the inline pump to test the inline pump, use this opportunity to blow out the crud in the fuel rail out the open line and also pump out crud in the tank line from the intake pump. Is there a schraeder valve on the fuel rail for pressure testing?

    If there is a lot of crud in the fuel rail, I would remove the fuel rail and all injectors and back flush and test them and replace all the fuel filters to prevent new crud from getting in.

    There could also be a plugged fuel filter between the in-tank pump and the inline pump that would cause the inline pump not to pump. I would jump all over the offer by kzhurley and use his factory service manual to trouble shoot this. I could not find very good info. on the '77 and fuel injection diagrams on the internet
     
  5. kzhurley

    kzhurley Active Member SUPPORTING MEMBER

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    I could also scan them and send email to you. Thats if I can figure out my scanner lol
     
  6. 5one9

    5one9 Active Member

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    What vehicle(s) do you drive?:
    2007 Magnum SRT8, 1957 F100
    Alt-Ctrl-Del
     
  7. kzhurley

    kzhurley Active Member SUPPORTING MEMBER

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    Full of info. I'm away from my scanner right now but I think I'll scan it and see if there's a way to post it for people to download it.. I suppose its legal? Lol
     

    Attached Files:

  8. Fleetwood

    Fleetwood New Member

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    I'll take that book, how much to 98233?
     
  9. kzhurley

    kzhurley Active Member SUPPORTING MEMBER

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    Pm sent
     
  10. Bruce Roe

    Bruce Roe Member

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    That is the best book on 70s Cad EFI. Can be found on Evil Bay, I also have
    spare copies. The Ign turns on the ECU, the ECU turns on pump power only
    when the engine is turning or for a second with Ign turn on, for safety. The 2
    pumps are on the same circuit, also controlled by the same circuit is the cold
    idle air valve on top of the throttle body.

    The EFI has no control over the HEI, but the SPEED SENSORS mounted low
    on the HEI trigger half the injectors on alternate crank revolutions. The pump
    circuit tends to burn out the ECU contacts, but I have a $10 kit to avoid or
    repair the problem (or make your own copy).

    I repair broken 70s Cad ECUs.
    Bruce Roe bcroe@juno.com CLC # 14630
     
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