94 VFR750 fell over now wont run

Discussion in 'Mechanics Garage' started by carbidetech, Sep 23, 2012.

  1. carbidetech

    carbidetech New Member

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    I tipped my bike over in the garage. It ran perfect before that. I have been repairing the damaged plastics for the last couple of weeks. Thought I'd fire it up just to hear it run and now it won't start. Turns over just fine and even started to run for a minute but before it warmed up it just stalled and now it wont start. Turns over just fine and i have spark too. Does anyone know how to check the fuel pump to see if it's working? I can see gas in the fuel filter as I normally do.
     
  2. crustyrider

    crustyrider New Member

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    check your fuses.... if it sputters to life there is no tip switch.... you may have a stuck float....
     
  3. carbidetech

    carbidetech New Member

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    Fuses are good. I may have fouled or flooded it not to mention it's cold today. Lower 50's. I'm going to let it set overnight and try again tomorrow.
     
  4. carbidetech

    carbidetech New Member

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    Well i decided to open up the drain screw on the left front carb and nothing but a dribble came out. Same with the rear left. Left the screws open and hit the starter button. No gas came out and i didn't hear the fuel pump running. Is there a tip-over switch or could the relay be bad? I unplugged the fuel pump and connected a volt meter to the wire harness to see if the pump was getting juice. The voltmeter would spike to 3v when i let go of the starter button but i'm not sure what I'm looking for.
     
  5. crustyrider

    crustyrider New Member

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    you can jump the fuel pump so that you have constant power....
     
  6. squirrelman

    squirrelman Member

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    "fuel pump relays fail far more often than pumps and can be eliminated with a single wire or paperclip," quoting myself.
     
  7. kennybobby

    kennybobby New Member

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    That was a smart move to check for fuel in the carb bowls.

    The fuel cut relay, aka fuel pump relay, gets its control signal (red/yellow wire) from the ignition control module and shares the same control line as ignition coil #4. So you can check for spark on #4 to know if the pulse counter and ignition control module are working okay.

    As Crusty mentioned you can bypass the relay to run the fuel pump. i would just do that as a test, not for riding purposes. Verify that the fuel pump will run when voltage is applied and fuel is pumped.

    If the control signal is firing and the fuel pump is working then the fuel cut relay is suspect.
     
  8. carbidetech

    carbidetech New Member

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    Well, shoot. #4 (front right cylinder) is not firing at all. I jumped the fuel pump and it primed the float bowls and it fired right up. I let it run for about a minute and carefully touched each header with a wet finger. All were too hot to touch except for #4 which was cold.

    Now what do i do?
     
  9. kennybobby

    kennybobby New Member

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    Some things you could try:

    Hook up a voltmeter to measure the voltage on the red/yellow wire at the fuel cut relay. When you turn on the key it should read 12 volts, when you hit the ignition switch the voltage should pulse down to zero and back up to 12. The best way to really see it is with an oscilloscope, but if the meter reads solid without jumping around then the ignition control module for cylinder 4 is suspect.

    Try disconnecting the connector or just the red/yellow wire to the fuel cut relay. Then start it up and see if cylinder 4 is getting hot. Maybe the fuel cut relay is shorted to ground and keeping the coil from firing. Obviously you will need to prime the carbs by jumping the fuel pump before doing this--the fuel pump will be off while it's running for a short time.

    Check the isolation of coil 4 to chassis/ground. Measure resistance between either spade terminal to chassis--it should be very high, open circuit. If the coil is shorted to chassis/ground then it will not fire and will probably interfere with the fuel cut relay also.

    Your problem is either the igniter channel 4, the fuel cut relay or the coil #4, or the wiring/connectors between these components.

    What side did it fall over on? Check for the wiring for a short to chassis or disconnected connector on the ignitor.

    Whare are you located? Maybe one of the guys can give you a hand. That's all i got, good luck to you.
     
  10. carbidetech

    carbidetech New Member

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    Thank You!

    The ground to coil #4 was cut in half.
     
  11. kennybobby

    kennybobby New Member

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    Do you think the cut wire was from the tip over, or how?
     
  12. crustyrider

    crustyrider New Member

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    you wold have to look at how it was cut... what sort of damage was incured atfer the fall over...sometimes shit happens.... way to getting it figured out....
     
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