47–04 LNG Vacuum Integrity
Testing
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.
1. Ensure the fuel tank is between 50 and 75
percent full.
2. Check the fuel tank pressure gauge,
Fig. 7, item
8, to ensure that pressure is within the normal
range of 120 to 150 psi (827 to 1034 kPa).
3. Inspect the fuel tank for signs of frost spots or
outer surface sweating. Frosting or condensation
on the outer surface of the fuel tank may indicate
a loss of vacuum.
4. Check for a large variance in temperatures
between the fuel tank and the fuel tank shroud. A
large variance in temperatures between the fuel
tank and the shroud may indicate a loss of
vacuum.
5. Operate the vehicle for ten minutes. Shut down
the engine, apply the parking brakes, and note
the time.
06/29/2009 f470536
2
5
6
7
8
9
10
11
12
1
3
4
1. Pressure Relief Device
2. Fuel Inlet Line
3. Check Valve
4. CNG Quick-Connect Port
5. Coolant Inlet Line
6. Vaporizer
7. Fuel Shutoff Solenoid Valve
8. Coolant Outlet Line
9. Pressure Gauge
10. Overpressure Regulator
11. Pressure Relief Valve
12. Fuel Outlet Line
Fig. 8, LNG Vaporizer Assembly
Fuel 47
Business Class M2 Plus Maintenance Manual, 02/10/2023 47/7
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