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    1993 Lincoln Mark VIII 4.6L SFI DOHC 8cyl

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    Fuel Injector

    Inspect/Test/Service/Replace

    A visual check often shows obvious problems, such as disconnected or damaged hose or wires. Electrical connections sometimes become corroded. Take the connections apart and look for corrosion.

    Disconnecting and reconnecting electrical connections sometimes solves the problem.

    Taking the connections apart and putting them back together is sometimes enough to improve the electrical connection and solve the problem.

    NOTE
    Plastic electrical connections often become brittle with age. Handle them carefully.

    Common Indications of Injector Problems:

    • An injector that does not open causes hard starts on port-type systems and an obvious no-start on single-point TBI (throttle body injector) designs.
    • An injector that is stuck partially open causes loss of fuel pressure (most noticeably after the engine is stopped and restarted within a short time period) and flooding due to raw fuel dribbling into the engine.
    • In addition to a rich-running engine, a leaking injector also causes the engine to diesel or run on when the ignition is turned off.
    • Build ups of gum and other deposits on the tip of the injector can reduce the amount of fuel sprayed by the injector or they can prevent the injector from totally sealing, allowing it to leak.
    • Since injectors on MFI (multiport fuel injector) and SFI (sequential fuel injection) systems are subject to more heat than TBI injectors, port injectors have more problems with tip deposits.
    • Because an injector adds the fuel part to the air/fuel mixture, it is obvious that any defect in the fuel injection system will cause the mixture to go rich or lean.
    • If the mixture is too rich and the PCM (powertrain control module) is in control of the air/fuel ratio, a common cause is that one or more injectors are leaking
    • An easy way to verify this is to use an exhaust gas analyzer.
    • When fuel injectors get dirty, this can cause the engine to ping at full throttle.
      • Use a stethescope to listen for different sounds between the injectors.

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