Fuel Filter: Testing and Inspection
1. Relieve fuel system pressure by slowly and carefully loosening one of the banjo bolts on the filter. Cover or wrap fuel connection with a clean rag while loosening to avoid spraying fuel.
2. Remove filter.
3. Blow air through the filter in the normal direction of fuel flow. If any restriction is felt, replace filter.
Also check service records. Replace filter as indicated by recommended maintenance, even if filter checks OK.