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Crusader electronic engine control

Discussion in 'Electronics' started by Brock_71, Jun 5, 2019.

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  1. Brock_71

    Brock_71 New Member

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    ohio
    I have a pair of 2007 8.1L Crusaders. less than 100 engine hrs. Replaced fuel filter . Spark plugs under 20 hrs. Ran ok last fall. Now The sync controller is malfunctioning causing the slave engine to run about 100rpm lower than the master. This happens at cruising speed and at the dock in neutral. Tested up to about 3400rpm.

    My Murphy digital display shows the throttle position feedback looking good with engines off.. It also displays RPM so the engines are sensing RPM and throttle position.

    I see a thing called a TAC control module that actually controls the throttle body. Could this be bad? Some GM forums say these go bad all the time.
    I wonder if it is the same as a GM part. For that matter maybe the whole throttle body is a GM part? Would be less expensive for sure than Crusader parts.

    Any thoughts on troubleshooting this or replacing parts with GM at a lower cost appreciated.

    Thanks
    John
  2. Capt Ralph

    Capt Ralph Senior Member

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    Frak, I hate gas engines. But I have been here many years ago.
    Early 8.1s had a distributor.
    Replace your distributor rotor and ensure the inside of the cap is clean and dry.
    Later 8.1s (coils on top of the valve covers) picked up from the harmonic pulley. Clean all rust flakes on the back side from this area.
    After this, report back.
  3. Brock_71

    Brock_71 New Member

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    OK. Will look at coils and rust. These are pretty clean engines in fresh water, but a bad connection cannot be ruled out.
    Engines are fuel injected with electronic throttles. No distributers.
    Thanks
    John
  4. Brock_71

    Brock_71 New Member

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    Two other points of info.. The slave engine that is running 100RPM low in sync mode also sometimes hunts at idle after a long run. Idle moves up and down. Never see this unless run for a few hours at cruise speed. Does not always happen though even after a long run.

    Tried taking the drive belt off a hydraulic pump on the slave motor. Then it did sync with the master motor. Rpms matched. Belt on it runs slow. Pump turns freely by hand.

    It seems the slave is sensitive to load, but surely the sync control should be looking at RPM and adjust for that. I would expect.
    Thanks
    John
  5. Brock_71

    Brock_71 New Member

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    I found no rust.
    Murphy display says there are no stored codes.
    Where is the Throttle Actuator Control (TAC) located?
    Is it right next to the on engine fuse box at the rear of the engine?

    Thanks
    John
  6. SeaLion

    SeaLion Senior Member

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    You might try calling Engine Distributors Inc. in NJ. I dealt with them a while back and they were knowledgeable and helpful.
  7. Capt Ralph

    Capt Ralph Senior Member

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    So on the engines, there is NO throttle cable to a control box in the engine room?
  8. Capt J

    Capt J Senior Member

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    Are you sure the 100 rpm difference isn’t just in your tachs?
  9. Brock_71

    Brock_71 New Member

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    There is a throttle cable on the engine, but it is only connected to a position sensor (pot). The cable is not connected to the throttle body mechanically in any way.
    The throttle position sensor is connected to a throttle actuator control module that is connected to a computer module and to a motor on the throttle body. The motor moves the actual throttle on the throttle body.
    The computer is also connected to a CAN bus serial link that connects to the other engine's computer and a Murphy digital display on the helm. All networked together.
    So this is truly "fly by wire".
    Great until it isn't.
    John