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  1. #1

    Question Cummins QSB5.9 engine does not start

    I have a QSB5.9 cummins engine,it was working perfectly. After several starts and stops, now the engine does not want to start and has a sound alarm.
    Anyone know what can it be?

  2. #2
    Join Date
    Jun 2008

    Default Re: Cummins QSB5.9 engine does not start

    It can be a lot of things but my first check would be the fuel filters and to reprime the fuel system. After that you could be looking at lots if different sensors but a complete no start rather than poor running would make me check the crank angle sensor as one of the first thoughts.

  3. #3

    Default Re: Cummins QSB5.9 engine does not start

    Hi. Thanks for your help, I will start the diagnosis by that sensor,I was looking for the wiring diagram of cummins QSB 5.9 but I only got the cummins ISX, is it the same?
    Thanks for everything

  4. #4

    Default Re: Cummins QSB5.9 engine does not start

    Good morning, please someone can tell me where to find, the following documents: QSB 5.9 CM850 Smarcrft 2.x Wiring Diagram

    Thank You..

  5. #5

    Default Re: Cummins QSB5.9 engine does not start

    Hello, have you solved you problem? If diesel generators fail to start, you can analyze the causes from fuel system failure, electric starting system failure, insufficient compression pressure in the cylinder and the low ambient temperature and other factors.

    1. Air in the fuel system
    This is a common problem that a diesel generator fails to start normally.
    Solution: Check whether the fuel oil pipe connector is loose or not, and ensure that the air is cleared from the fuel system. Loosen the bleed screw bolt on the diesel filter, and then use the manual oil pump to pump the fuel until the air bubble is gone.
    2. Fuel Line Obstruction
    Solution: Check whether the pipeline is smooth or not.
    3. Fuel Filter Clogging
    Solution: Clean the filter or replace the filter element
    4. The Handle Position of Fuel Injection Pump Is Not Correct
    Solution: The handle position should be pushed to no-load when starting the diesel generator set. Rotation speed is about 700-900r/min.
    5. Fuel Injector Problem – Little fuel injection or fuel injection is not atomized
    Solution: Remove the fuel injector, connect it to the high pressure oil pump, pry the fuel injection pump plunger spring and observe the spray condition. If necessary, wash the injection pump.
    6. Oil Supply Problem – Oil transfer pump doesn’t supply oil or the oil supply is brokenly.
    Solution: Check whether the oil inlet pipe is leaked or not and the filter screen on the oil inlet pipe connector is blocked or not.

    Electric Starting System Failure

    1. Battery Power Shortage
    The most common failure for diesel generator is battery failure.
    Solution: Use the battery with sufficient power, or increase the battery to use in parallel. Replace the new start-up battery if necessary.
    2. Circuit Wiring Error or Poor Contact
    Solution: Check whether the wiring is correct and reliable.

    The compression pressure in the cylinder is insufficient; fuel injection is normal but does not catch fire; or fuel oil inside the exhaust pipe

    1. Excessive wear of piston ring and cylinder liner
    Solution: Replace the piston ring, and replace the cylinder liner according to the wear condition.
    2. Valve leakage
    Solution: Check the valve clearance, vlave spring, as well as the sealing of the valve guide and seat. If the seal is not good, you should make a repair.
    3. Combustion chamber volume is too large
    Solution: Check whether the piston belongs to the model, if necessary, measure the combustion chamber volume.

    Click image for larger version. 

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