Usage:
3406, 3406B Truck Engines
Some OEM's (Original Equipment Manufacturers) supply a disposable primary fuel filter in place of the Caterpillar primary filter. The mesh of the pleated paper used in these disposable filters is smaller than the screen mesh in the Caterpillar primary filter. As a result, the disposable primary filters have a shorter service life than the Caterpillar primary filter.
The smaller mesh of the disposable primary filter in a like new condition has not been known to cause excessive fuel transfer pump inlet restriction, or any other fuel system-related problem. If questions arise, the inlet restriction can be checked. Check the restriction where the vehicle fuel supply line is connected to the engine. A new, clean primary filter must be used when checking the restriction. The filter is acceptable if the total inlet restriction is not more than 30.4 kPa (9.0 in. Hg).
The frequency and severity of fuel waxing and plugging of the disposable primary filter will be similar to that for the final filter.