Easy WAy to Take TFI Out of Circuit

Discussion in 'TFI Questions Answered By Dobeck' started by RibEye, Mar 29, 2011.

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  1. RibEye

    RibEye Junior Member Contributor

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    I am an electronic and software engineer, so forgive my technical terminology. I am having an issue that requires a process of elimination. The issue is far too intermittent to allow an easy determination of fault.

    I do not believe my problem is the TFI, but I want to eliminate it as a possibility. It is fairly difficult to physically remove it, and I don't want to just turn some pot settings. I want to eliminate its function, but leave it installed. Is that possible?

    I have been told that you can just disconnect its ground wire. That makes some sense to me, in that, the injectors are low-side driven, and the TFI injector drive contribution could easily be hard-wire OR'd with the ECU injector drivers. Is this true?

    In any case, is it safe to disconnect the TFI ground wire and run it that way for a week or so? My problem is very intermittent, but significant when it occurs, and I may need time to see it occur with the TFI out of the circuit. Sometimes the issue (stuttering and misfiring) does not occur for 70-90 miles.

    Thanks in advance,
    Rich P
     
  2. Bud White

    Bud White Well-Known Member Retired Moderators

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    yes you could do it like that but remember your creating a lean condition..

    have you checked the injector wires 4 a break in the wire you have to feel it as it will be broke coating wont .. will cause intermittent probs
     
  3. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Have you eliminated a physical cause of this such as described here:

    Engine Dies And Runs In Spurts - Harley Davidson Community

    TQ
     
  4. glider

    glider Veteran Member

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    No problem disconnecting the ground wire, the bike will revert to the base map in the ECM.
     
  5. DobeckTechSupport

    DobeckTechSupport Active Member Product Contributor

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    Just confirming as stated above from a few users that simply disconnecting the ground wire from a TFI or GEN 3 is just like removing the unit. The bike will be able to start and function off the stock ECU map. This is dependent on the assumption that a wire is not broke on the harness.
     
  6. RibEye

    RibEye Junior Member Contributor

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    Thank you for your quick and definitive response. As I said, I do not believe the TFI is faulty. I will be looking forward to putting it back into service, as soon as I can.

    Thanks for the other confirming contributions.

    Enjoy,
    Rich P

    The issue is generally rare and occurs in brief bursts when it happens, it appears to like light acceleration to cause it, but I'm not sure there. Fuel rail pressure measures good and stable, I do not believe I have a hole in the internal fuel line. That does not eliminate other possibilities in fuel pressure: intermittent problem with fuel pump, blockage in the fuel tank vent line, obstructed fuel filter, kinked fuel line, etc. Each to be eliminated as possibilities in their time.

    Enjoy,
    Rich P

    I have dropped back to the stock air box, so the lean condition will be the factory, EPA mandated, lean condition. She should handle it, since it is a nice cool spring.

    I have not physically checked the injector wires. That is a check that is near the top of the list of items to check/eliminate. If I could get an ECU breakout box, that would make such checks so much more easy. Limp on, I shall.

    She is not throwing or historically storing any codes, so checking things that would throw codes, like sensors (MAP, TPS, CKP, etc), are moved a bit lower on my check/eliminate list. Since she is not thowing codes, for now, I'm concentrating on items which do not directly feed back to the ECU (injector wires, injectors, spark wires, coil or its supply wires, etc.). Intake leak, spark plugs, and exhaust leak have been eliminated.

    Enjoy,
    Rich P

    Folks,

    I do appreciate all of your suggestions. I have already done some of them, and have incorporated the rest in my diagnostic plan.

    The purpose for this thread has been accomplished. I don't see any reason that Dobeck support should be bothered any further with my issue.

    I will update an appropriate thread in another area of the board, when there is more to report or request. I fully intend to provide whatever I learn along the way, so others can benefit.

    Thanks to all,
    Rich P
     
    Last edited by a moderator: Mar 30, 2011
  7. glider

    glider Veteran Member

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    Rich, to make it easier to follow the problem, just continue in this thread instead of starting another one.:s
     
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