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For a schematic diagram of a typical fuel system, see Figure 24393 . ‪

Schematic Diagram of the Fuel System

The fuel system includes injectors, integral fuel manifold in the cylinder head, fuel pump, a cooling plate for the Electronic Control Module (ECM), a primary fuel filter, a secondary fuel filter, and a fuel shutoff valve if equipped. An 2.0 mm (0.080 in.) restrictive orifice is located in the fuel return fitting at the rear of the cylinder head to maintain the pressure in the fuel system. ‪


To avoid injury from fire, contain and eliminate leaks of flammable fluids as they occur. Failure to eliminate leaks could result in fire.


To avoid injury when working on or near an operating engine, wear protective clothing, eye protection, and hearing protection.


Diesel engine exhaust and some of its constituents are known to the State of California to cause cancer, birth defects, and other reproductive harm.

  • Always start and operate an engine in a well ventilated area.
  • If operating an engine in an enclosed area, vent the exhaust to the outside.
  • Do not modify or tamper with the exhaust system or emission control system.


To avoid injury from fire, keep all potential ignition sources away from diesel fuel, including open flames, sparks, and electrical resistance heating elements. Do not smoke when refueling.

Fuel is drawn from the fuel tank through an optional fuel water separator, into the primary fuel filter and enters the pump. After leaving the fuel pump under pressure, the fuel flows through the ECM cooler plates (if equipped) through the secondary fuel filter to the cylinder head. ‪

An optional PRO-CHEK check valve that removes air from the fuel supply line may be installed between the secondary filter and the cylinder head. The fuel flows to the injectors in the cylinder head through passages integral with the head. Surplus fuel exits at the rear of the head just above the inlet, through a restrictive return fitting which maintains fuel pressure in the system and returns back to the fuel tank. ‪