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Thread: STILL DOESNT RUN! XB9 PUZZLE

  1. #1
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    I'm restarting my thread. - 2005 xb9 Lightning city.
    Bike died while driving in 3rd gear like I turned the key off. Got the "Chuck engine light" onthe way down.
    -Fuel pump doesnt run (NEW Since problem started)
    -12V to the coil connector but fails the trigger signal test to the two outside wires on the coil connector.
    -Voltage to first sensor starts with .7V and rises as I unplug them to a max of just under 3 V with all unplugged. -Speed, cam, Bank angle, inlet temp, & TPS. Is there another sensor?
    -Fuel pump has around 12V but doesnt run unless I connect directly to battery. (If I jumper the ground side direct to good ground it runs constantly when key is turned on).
    -checked ground wires with ohm meter and readings all at least .4 or better (Good)
    -all grounds removed and frame and wire side all sanded with emory cloth.

    Lots of symptoms but no answers! HELP!!!
    -battery is one week old and cranks motor fast (220 cca). Cables clean and tight.

  2. #2
    Senior Member d_adams's Avatar
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    (If I jumper the ground side direct to good ground it runs constantly when key is turned on).
    That RIGHT THERE should be where you start looking. Check your grounds. Again. Use a heavy gauge jumper wire, run from the negative post to a new ground spot on the frame and try it again.

  3. #3
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    The ground wire from the pump runs through the harness directly to the ECM which handles the ground through some internal electronic switching as best I can tell. The ECM has two ground wires, A & B, which have both been checked with an ohm meter showing them to be extremely good. (Both have been cleaned and tightened as well). The ECM does not ground this wire until the ignition is switched on.
    I originally focused on the Pump not running, but the low voltage to the sensors tells me there is something else going on. Any ideas?

  4. #4
    Senior Member thrstrmech's Avatar
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    ignition switch may be the issue since it completes circuit, did you ring out the ground from the ignition switch, main harness and the switch itself?

  5. #5
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    Yep, did wiggle test, no trouble there. I do have 12V at the 3 prong coil connector, but it fails the trigger test on the 2 outside wires.

  6. #6
    Senior Member nicholas900's Avatar
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    I got your PM July4. I'll try and help.

    Sorry if I have you test things you already did. I'll list a few steps at a time to cut down the back and forth. We'll figure it out.

    Let's start with the fuel pump that doesn't run. It has 4 wires, two for the low fuel light and two for the motor. We just care about the two for the motor right now. Key on. Unplug the fuel pump connector. You should have 12v ( battery voltage ) on the gray wire bike side. Check with your testers black lead on the battery ground, red lead on the gray wire. This is the same gray wire on your coil and injectors. Check in those spots and verify 12v on the gray wire.

    Next with the fuel pump still unplugged. Key on. Connect your volt meter leads to the Gray wire and Brown Yellow on the bike side connector. You should see battery voltage as the gray wire is + and the Br/Y wire is the ECM ground. If you have battery voltage good. Skip next test and report back.

    If not repeat same test, but to rule out a bad BR/Y somewhere in the harness . So hook up your tester red lead to the gray wire at fuel pump bike side connector and the testers black lead to the BR/Y wire at the ECM's black connector. Keep the ECM plugged in.

    What u got?

  7. #7
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    The gray wire on the FP harness measures nearly full battery voltage, about 12.7V nice and steady no drop. if I use the battery ground for the tester. This is where it gets weird, If I put the tester wires to the FP harness only, + to gray and - to BN/y I get 12.1 and then it starts dropping, i.e. 12.19, 12.18, 12.17 and quickly goes below 12V, slowing down around 11.7V.

    I've tested the BN/Y wire from the harness to the plug on the ECM with a good FLUKE $$ meter and it shows a solid reading of .36 on the ohm scale. (I get a reading of .29 if I take a reading from one part of the subframe to another for comparison sake of the number).

    Not sure if you skipped ahead, but I tried to put the other tests I did as bullet points at the begining of this thread. This is all stuff I did last night, so it is recent.

    So glad you are jumping in on this.

  8. #8
    Senior Member thrstrmech's Avatar
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    This is where it gets weird, If I put the tester wires to the FP harness only, + to gray and - to BN/y I get 12.1 and then it starts dropping, i.e. 12.19, 12.18, 12.17 and quickly goes below 12V, slowing down around 11.7V.
    fuel pump harness only.... hmmmm, k, ring out each of the wires on the fuel pump harness. wonder if the grommet in the pump housing is torn/cracked and or wire is chaffed and rubbing/touching the housing. you can push the fuel pump harness assembly out of the fuel pump housing and have a look to rule it out. think I already asked for you to look at the pins in the connector for broken wires on both ends.
    I'd almost want to start removing sheathing off the wire harnesses and look for chaffed and or partial severed wire(s) as well.

  9. #9
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    No, I don't mean FP harness by itself. I mean plugged into the main harness, connecting test leads to + and - of the harness while plugged in and key on. as compared to jumpering around the ground wire in the harness.

  10. #10
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    The red/white wire for the sensors has only 2.67 V with all the sensors disconnected. It should be 5 V. This wire checks out well with the Olm meter; good conductivity and no bleed over to ground with sensors disconected. I switched to the other ECM I have and the reading is almost exactly the same, (2.60V). This should be a huge clue, but I do not know what to make of this information. Is the ECM bad and I just happened to have aquired another one with the exact same fault? Seems unlikely, but I'm open to anything. The obvious question here is why do I have only 2.67V on the sensor circuit with all the sensors unpluged??



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