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This illustration show you guide on how to perform idle speed balance test for Detroit Diesel GHG14 engine.
Incorporated into the MCM is the Idle Speed Balance (ISB) software which monitors the crankshaft speed variation per cylinder power stroke and compensates each fuel injector to allow for a smoother running engine at idle. The compensation values can be learned and stored in the EEPROM. ISB values are the percentage of adjustment that the MCM can make to a fuel injector to adjust for idle stability. It does not represent the total amount of available fuel per cylinder.
For diagnostic purposes, these values can be used to pinpoint a cylinder which is getting close to or at its maximum/minimum limit. The limit values are set to positive (+100) and negative (-100). A value above or below the acceptable limit indicates that the MCM software is compensating for a crankshaft speed variation. On a common rail system this can be caused by internal engine damage, fuel injector fueling issue or failure of a high pressure supply to a particular fuel injector.
If the ISB values are 0, this indicates no fueling compensation is needed. Values of +40 and -40 are not uncommon for a new fuel system. If values reach +70 or -70, injection quantities are reaching their limits and should be noted. If values are at +100 or -100, the respective cylinders should be checked for a failed component.
For example, for a low injection rate (low fueling from fuel injector), the software will try to compensate for this fuel injector by increasing its pulse width to smooth out the engine. The value will go positive until the engine is performing properly. If the value reaches (+100), no more compensation can occur. The fuel injector should only be replaced after a visual inspection of the fuel supply to the fuel injector is checked. If the value reaches (-100), this would indicate that the fuel injector is over-fueling to the point that the software cannot take out any more fuel.
Note : Mechanical failure can also cause a +100 or a -100 reading of ISB. Follow all of the troubleshooting procedures for the particular system to determine the root cause of the failure.
Related Contents:
2023 Detroit Diesel Diagnostic Link DDDL 8.17 8.09 Free Download
Checking Idle Speed Balance
Check as follows:
Note : Fuel temp must be at least 10
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