Diesel Fuel Contamination

Various malfunctions in diesel engines often lead to injection pump replacement. Before replacing the injection pump, determine if water or an excessive amount of gasoline is the cause of the malfunction. If water or gasoline is found to be the cause of the malfunction, injection pump and injection nozzle replacement may not be necessary. The following procedure should help to eliminate unnecessary pump and nozzle replacement in the event of fuel contamination.
• First, remove the engine fuel filter and inspect the contents for the presence of water or gasoline. If water or gasoline is found, flush the system as outlined on the following page.
• Fuel contamination should be expected if the car stalls, performance is poor or in the case of gasoline, the engine will knock loudly.
• If gasoline is suspected, remove the fuel fill cap and check for the presence of gasoline fumes.
• Gasoline will not harm the injection system. Flush the gasoline out of the system as outlined. Do not remove any injection equipment unless engine operation is unsatisfactory after the system has been flushed.
• For water, remove the engine fuel filter and inspect the contents for the presence of water. If water is found, remove the injection pump cover. If the pump is full of water, flush as outlined on the next page.
• Small quantities of surface rust in the injection pump will not create a problem. If the vehicle stalls as a result of contamination, remove the metering valve and polish it lightly with 600 grit paper to remove the contaminant. If the advance piston is stuck as evident by poor performance, smoke or noise, it may be necessary to remove the pump to free it up.
• Occasionally contamination may enter the system that becomes so severe that physical damage has occurred to the springs and linkage in the pump. These pumps that require part replacement should be returned to a Stanadyne shop for repair.

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