3500 4x2 Pickup L6-359 5.9L DSL Turbo (1994)
Fuel Filter: Testing and Inspection
A blocked or clogged fuel filter/water separator can cause starting problems and prevent the engine from revving up. It can also cause, low power and
blue or white fog like exhaust.
The maximum allowable fuel pressure drop across the fuel filter/water separator is 35 kPa (5 psi). This can be checked with a fuel pressure gauge.
Fuel Pressure Gauge Attaching Points
1. Attach the gauge to the inlet side of filter/separator at the fuel line leading from the fuel transfer pump. Measure pressure with the engine running.
2. Attach the gauge to the outlet side of the filter/separator at the fuel line leading to the fuel injection pump. Measure pressure with the engine
running.
3. Compare the pressures. It must not exceed the previous specification.
If the instrument panel mounted water-in-fuel warning lamp is illuminated with the ignition key ON, it indicates that excess water has collected in the
fuel filter/water separator. Excess water can be drained. Refer to Service and Repair for water draining procedures.
If excess water gathers in the filter/separator in a short period of time, the fuel tank must be removed, drained and cleaned.
