Engine
70
FUEL SySTEM
Description
The fuel system includes the tank, pump, filters, and feed and return lines. The fuel pump provides
pressure to move fuel from the tank to the unit injectors and draws fuel through the supply line, check
valve, strainer, and filter. Fuel then passes through the fuel pump and goes to the injectors in the cylinder
heads. Surplus fuel is returned to the fuel tank through the return line.
Fuel in lines or other components can be under dangerously high
pressure. Always take precautions to avoid injury from fuel under
pressure when working on the fuel system.
Common Problems
Water Contamination
It is normal for small amounts of water to collect in the fuel tank due to condensation. However,
constant water contamination of the fuel system indicates a problem with the storage or passage of fuel.
Do not allow water to accumulate in the system. If it does, drain and clean the fuel tank and fuel lines
and replace the fuel filters. Drain the primary fuel filter often, as explained later in this section.
Algae formation is another danger to the fuel system of a diesel engine. Algae can clog the fuel filters
and injector nozzles. Since algae must have water to survive, it is important to keep water out of the fuel
system. It is advisable to purchase fuel from reputable dealers where there is a regular turnover and the
fuel does not stand for long periods. Try to keep the fuel tank topped off to prevent moisture condensa-
tion, especially if the coach will be parked for a long time.
Air in the Fuel System
Air drawn into the fuel system can result in rough running, stalling when idling, or a loss of power. An
opening in the fuel supply line may be too small for fuel to pass through but could allow air to enter. Use
the following procedure to check for air in the fuel system:
1. Disconnect the fuel return line from the connector at the front of the engine compartment bulk-
head. Do not disconnect the line at the bracket on top of the engine.
2. Immerse the end of the return line in a container of fuel, then start the engine.
3. Air bubbles rising to the surface indicate air is being drawn into the fuel line connections be-
tween the fuel tank and pump. Check for damaged lines and repair or replace as necessary.
4. See information in “Fuel Filters” on the next page.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...