Purpose
To check fuel level and quality for efficient engine operation
• Ask the operator if the amber WATER IN FUEL lamp was on during vehicle operation.
• If engine has an optional Engine Fuel Pressure (EFP) sensor, ask the operator if the amber FUEL
FILTER lamp was on during vehicle operation. If the lamp was on, change the fuel filter and retest for poor engine operation.
Tools
• Clear container (approximately 1 liter or 1 quart US)
• Fuel pressure test adapter
• Pocket screw driver
Procedure
1. Check fuel level in fuel tank and for odors other than diesel fuel – kerosene and gasoline, for example.
CAUTION: Be sure to place a rag or suitable container under the fuel pressure test valve when bleeding the
fuel rail. Dispose of fuel in a correct container clearly marked DIESEL FUEL according to local regulations.
NOTE: Engine fuel can be a threat to the environment. Never dispose of engine fuel by putting it in the trash, pouring on the ground, in the sewers, in streams, or bodies of water.
NOTE: Engines are equipped with a fuel pressure test valve in the form of either a Shrader valve or a
diagnostic coupling.
2. Check for indications of aerated fuel in the fuel system. Relieve pressure from the fuel rail using
the fuel pressure test valve.
• As fuel pressure is relieved, a steady stream of fuel, without air from the fuel pressure test valve, means that air is not in the fuel system.
• An erratic air/fuel mixture surge suggests that air is in the fuel system.
NOTE: It is recommended to use the fuel pressure test adapter to avoid bending the needle in the fuel
pressure test valve.
NOTE: Some engines will have a diagnostic coupling instead of a Shrader valve. Press end of coupling with
a pocket screwdriver to relieve pressure.
3. Open water drain valve and collect a fuel sample using a clear container. Check for the following conditions:
• Fuel must be the correct grade, clean, and undiluted.
• Gasoline, kerosene or other chemicals in the diesel fuel (If diesel fuel is contaminated, correct the condition and retest.)
• If the fuel filter was not serviced or drained for a long time, some sediment or water could be in the fuel filter housing.
NOTE: Cold weather can cause fuel waxing in some grades of diesel fuel. Waxing will restrict or stop fuel flow through the fuel filter.
4. Open fuel strainer drain valve. Collect a fuel sample using a clear container. If fuel is contaminated do the following:
a. Pull drain valve down and out of bowl.
b. Remove strainer bowl and check strainer for sediment, debris, or rust. Clean and replace as required.
c. Check fuel tanks and fuel lines. Clean and flush if necessary.
5. Prime fuel system. See “Priming the Fuel System” in Section 4 (page 132) for procedure.
Possible Causes
• Low fuel level in fuel tank.
• Inline fuel valve (if equipped) could be shut-off.
• Fuel supply line could be broken or crimped.
• The fuel tank pickup tube could be clogged or cracked.
• Supplemental filters or water separators may be plugged or leaking allowing air to enter the fuel system.
• Failed seal for inlet fitting in fuel filter housing
• Water or contaminants in fuel tank
• Ice in fuel lines
• Debris in fuel tank
• Cloudy fuel indicates unsuitable fuel grade for cold temperatures.
• Fuel could be waxed or jelled. (usually Grade 2-D)
