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Thread: EFI arbitrarily turns off while driving.

  1. #1

    Default EFI arbitrarily turns off while driving.

    I called this issue out in different post on the EFI Throttle Bodies section. Hoping to get more attention to the concern here.
    BASELINE INFORMATION: Rover 4.2 liter V8 (think old Buick Aluminum 215). Possible mild cam or stock cam offset a few degrees (builder doesn’t remember) in a 1970 MGB-GT with 5-speed manual transmission.

    Edelbrock Performer Manifold
    2BBL Projection Throttle body that started life with an analogue ECU, since upgraded to 2D ECU (534-55), Closed Loop. (This all replaced a 390 cfm Holley Carb many, many years ago.)
    New style injectors, confirmed in good operating condition.
    New, tested, TPS currently installed.
    Crane Electronic Ignition module with matched Crane coil. GM points style distributor converted to optic trigger internals.

    ISSUE: Fuel injection turns off while in use. (i.e. When driving.)

    The car has been pretty solid for a few days so I though I found the issue when checking the connections at the ignition switch. They were loose and needed some cleaning up. Fixed that.

    Then last night after 15 minutes or so of driving I made a right-on-red that required a bit of enthusiastic acceleration. Once I settle down @ approximately 45 MPH the fuel stopped. I'm not sure if its the ECU or just the fuel pump. It's definitely not an engine stall.

    The conditions of the two more recent times this happened, one was similar to above, one was while trundling behind a landscape truck at 30 MPH.

    Car will restart every time. Engine temp is usually at 60° Celcius (140°F), Tach continues to read RPM, ignition light will only come late after engine turns off.

    I'm powering the ECU through a relay. All grounds have been checked and cleaned. Thoughts or shared experiences?

  2. #2


    After posting I went back and read all of the appropriate manuals, books, etc.

    Nowhere is what I'm experiencing listed in any troubleshooting. One can draw conclusions regarding tach signal or other wiring, but there's no conclusive issue/solution that I can find. (NOTE: All of the wiring was checked previously.)

    For what ever reason I decided to focus on the relay. I Googled "symptoms of a failing relay" and one search return was, "If your car shuts off while driving, the ignition relay can be to blame."

    Essentially driving the ECU via a relay is an ignition relay scenario so I swapped the China made one for a Lucas unit that I found in a spare parts draw. A successful one hour test drive followed but time will tell.

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