freightliner M2 Plus Maintenance Manual page 148

47
6. Wait fifteen minutes after shutting down the
engine, then record the fuel tank pressure and
note the time.
7. Allow the vehicle to stand for at least eight
hours, then record the fuel tank pressure again.
Pressure Increase Over Eight-
Hour Period
Less than 20 psi (138 kPa)
20 to 50 psi (138 to 345 kPa)
More than 50 psi (345 kPa)
47–05 CNG Fuel System
Inspecting
WARNING
Natural gas is highly flammable. See the safety
precautions listed in Chapter 16 of the Business
Class M2 Plus Driver's Manual or Group 47 of the
Business Class M2 Plus Workshop Manual.
Failure to observe these precautions could lead to
the ignition of the natural gas, which could cause
serious bodily injury or death.
The following inspections must be performed by a
qualified technician, in accordance with the
manufacturer's established inspection criteria.
NOTICE
Do not use a high-pressure washer or steam
cleaner on natural gas fuel system plumbing
components, as this can introduce moisture and
contaminants into the threads of the fittings and
damage the sealants.
Gas detection sensors are located on the cab
overhead console and in the engine compartment
on the frontwall. The sensors are located in high
areas, where rising gas vapors will pass by or
accumulate. Do not use a high-pressure washer,
steam cleaner, or silicone-based chemicals on the
gas detection sensors, as this may permanently
disable the sensors. When cleaning the vehicle,
cover the sensors with a plastic covering. Keep
47/8
Vacuum Integrity Test Results
None – Tank is normal
Monitor tank and test vacuum integrity again at next maintenance date
Remove vehicle from service and evacuate the tank per the tank manufacturer's
instructions
Table 1, Vacuum Integrity Test Results
8. Use Table 1 to determine whether the pressure
increase is within an acceptable range.
Remedy
the sensors covered until the area has been
cleared of any cleaning fumes. Harsh chemicals
and extremely high temperatures may damage the
sensor.
Use a bubble solution to check for leaks while
performing the following inspection.
1. Inspect the fuel cylinders for dents or other signs
of damage.
Replace any leaking fuel cylinders.
2. Ensure that the fuel cylinders are secured within
the fuel cylinder storage box.
3. Ensure that the fuel cylinder storage box is
secured to the frame. Inspect for any signs of
looseness. If necessary, tighten the storage box
mounting bolts 160 lbf·ft (217 N·m). See
NOTE: During initial pre-delivery inspection
(PDI), tighten the storage box mounting bolts,
shown in Fig. 9, 180 lbf·ft (244 N·m).
4. Inspect the fuel fill port for signs of damage or
leaks. Ensure the port dust cover and the O-ring
inside the port are both present and in good
condition. See Fig.
5. Inspect the pressure gauges on the fuel box for
cracks. Ensure the indicator needles are present
and in working condition. Inspect the gauge
faces for accuracy and legibility.
6. Ensure blue caps are present on all pressure
relief devices. Each fuel cylinder is equipped with
two caps (one on each end), which are visible on
the back of the CNG fuel cylinder storage box.
Business Class M2 Plus Maintenance Manual, 02/10/2023
Fig.
10.
Fuel
9.