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[WARNING] Use only fuel connections designed for use with that on the bus.
Do not attempt to force damaged fittings. Keep sources of heat and ignition
away from fuel system and refueling apparatus.
For more information, see drawing #1589001 in the owner’s information pack-
age supplied with the vehicle.
Compressed Natural Gas Fuel
The performance and reliability of a natural gas vehicle is dependent upon the qual-
ity of fuel used. BTU content of natural gas can vary depending on locale. Excessive
moisture can cause loss of power, and regulator freezing. Other contaminants, spe-
cifically lubricants and oil, can cause serious damage which is not covered by the
engine manufacturer’s warranty. In addition, poor quality fuel can affect emission
certification.
[CAUTION] It is the owner’s/operator’s responsibility to ensure that clean,
quality fuel is used to prevent damage to the fuel system components and
power plant. Damage caused by poor quality fuel is not covered by Blue Bird
warranty.
Fuel control systems used on engines fueled by compressed natural gas contain
electronic sensors and other delicate components that are not tolerant of contami-
nants. Vehicle performance is dependent upon clean fuel and a regular schedule of
vehicle maintenance.
Compressed natural gas is expected to be delivered from the compressor station
and storage cascade free of contaminants including oil, water, and particulates. Con-
ditions exist in some CNG fill stations that cause inferior fuel to load into the vehicle’s
fuel storage system.
Compressed Natural Gas Filters
Particulate and coalesce type filters are installed in Blue Bird CNG fuel systems. The
primary filter is of stainless steel construction and is located at the fill point. This filter
can be checked for contamination by closing the main shutoff valve on the frame
and then relieving pressure which is trapped between the check valve in the fill noz-
zle and the main system check valve. The owner/operator should establish a service
interval based on quality of gas from the compressor station. It is recommended that
the filter sump be checked after the initial fill and every fifth fill thereafter, or on a
schedule based on need.
The secondary filter has a black anodized housing and is adjacent to the fuel shut-
off solenoid close to the engine. The secondary filter can be checked after relieving
system pressure. This is best accomplished by closing the main shutoff on the frame
and running the engine until the fuel supply is depleted and pressure is zero. Con-
tamination of the secondary filter should not occur if a proper maintenance schedule
has been followed at the fill point primary filter. Contamination of the secondary filter
indicates that the CNG storage cylinders on the vehicle are contaminated. The owner/
operator should insist that fuel from a compressor station be clean and dry.
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