Fuel Filter - Testing for a Plugged Condition

Number 83-I-74 Section 6B Date 05/83
Subject: PLUGGED FUEL FILTER - 1980-1983 DIESEL ENGINES

A new diesel engine fuel filter cannot be checked for a plugged condition by simply blowing through it with your mouth. During the manufacturing process a percentage of the filters are checked with a light petroleum product. Air will not pass through a wet filter element as easily as one that is dry. Therefore, blowing through the filter with your mouth cannot be used as a test to determine if the filter element is plugged. Installation on the engine or regulated air pressure of 2-3 PSI is the only way to determine if the filter is plugged. Care should be taken not to use excessive air pressure when checking the filter or damage to the filter element can occur.