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Why Cummins QSB is difficult to start

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One Customer repair engine which fail to start, the dealer on-site inspection and replacement of fuel filter, the battery voltage is 25V, the starting speed of 180 rev / min, are normal, the current fault code: 559, fuel pressure is low. 

Cause Analysis
Possible causes of engine failure:

Check whether the fuel used by Mr. X is qualified. Unqualified fuel will cause the fuel filter to clog, and the fuel pump and the injector wear out.
Low battery voltage, internal faults, engine speed lower than 150 rpm;
The fuel filter is clogged, the inlet oil resistance is large, and the oil inlet is not smooth;
Key switch failure or line problem;  
ECM line or internal fault
Internal engine failure;

Demolition analysis process:
Field inspections of Mr. X's fuel tank, fuel injection and internal signs of rust on the fuel tank, oil filter separator FH238 bottom filter cup has a lot of impurities, fuel filter plug, before the replacement of the filter, the tank management to clean these, and then replace As a new fuel, start the engine, or cannot run, hand pump slightly pressurized, the engine car, everything is operating normally, in the demolition of the pressure side filter inspection, found that when using the hand pump to pump oil, the pressure side of the filter inlet, export are There is fuel outflow, analysis of the fuel pump return valve issuing, lax close, causing fuel leakage. The engine starts normally after the replacement.

Failure conclusion
Mr. X used a plastic bucket, loaded with unknown chemical raw materials, and put it into use without cleaning, causing secondary pollution of the fuel, causing fuel tank, pipeline rust, fuel filter plug, fuel pump return valve spool stuck in the open Position, when the engine is dragged, the fuel pump return valve leaks and fuel pressure cannot be established (fault code: 559), causing the engine to fail to start.  

Do not ignore the details during the use of the engine. A momentary oversight may result in a minor engine failure.