PUMP GP-UNIT INJECTOR HYD 3190678 - Caterpillar

All 3204 And 3208 EnginesA broken edge filter or a plugged cylinder head adapter can cause rough engine operation or low power. Under some conditions, it was possible for the edge filter to crack or break.
If a section of the edge filter breaks off, and it is larger than the orifice in the cylinder head adapter, there can be two results. First, the broken section can cause a complete restriction (plug) in the orifice of the cylinder head adapter as shown in Illustration 1. If the restriction is at the other end of the fuel passage, it can not be seen. To check for this condition, blow air through the inlet end of the adapter. See Illustration 2. A restriction in the air flow will be the result if there is a restriction in the fuel passage.
Illustration 1. Nozzle on the right has a restriction caused by a broken edge filter.
Illustration 2. Blow air through inlet to check for an internal restriction.A second result when a section of the edge filter breaks off is shown in Illustrations 3 and 4. The broken section of the filter is continually forced against the walls inside the adapter by the high pressure fuel. Each time the broken section of the filter makes contact with the adapter walls, small pieces break off and pass through the adapter and into the fuel nozzle. Illustration 3 shows what is left from a piece of the edge filter after it has been broken down by the high pressure fuel.
As the small pieces pass through the cylinder head adapter and the fuel lines for the fuel nozzles, the ferrules on the nozzles are damaged. Illustration 4 shows the effect of these small pieces on the ferrule surface.
New edge filters are used in the cylinder head adapters on 3204 and 3208 Engines. The new edge filters are stronger than the former edge filters. The part number of the cylinder head adapters has not changed. See Illustration 5 for identification of the cylinder head adapters with the new edge filters.
Illustration 3. Example of a broken edge filter.
Illustration 4. Fuel nozzle ferrule damaged by a broken edge filter.
Illustration 5. New and former edge filters.