6.4 Inspect the pressure gauge for damage.
Ensure that the gauge sight glass is clear
and legible.
7. Repair or replace any leaking or damaged vapor-
izer components.
47–05 LNG Vacuum Integrity
Test
WARNING
Natural gas is highly flammable. See the safety
precautions listed in Chapter 21 of the 108SD and
114SD Driver’s Manual or Group 47 of the 108SD
and 114SD Workshop Manual. Failure to observe
these precautions could lead to the ignition of the
natural gas, which could cause severe bodily in-
jury, death, or property damage.
1. Ensure the fuel tank is between 50 and 75 per-
cent full.
2. Check the fuel tank pressure gauge (
Fig. 9, 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 be-
tween 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.
6. Wait fifteen minutes after shutting down the en-
gine, 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.
8. Use
Table 1 to determine whether the pressure
increase is within an acceptable range.
Vacuum Integrity Test Results
Pressure Increase Over Eight-
Hour Period
Remedy
Less than 20 psi (138 kPa) None – Tank is normal
20 to 50 psi (138 to 345 kPa) Monitor tank and test vacuum integrity again at next maintenance date
More than 50 psi (345 kPa)
Remove vehicle from service and evacuate the tank per the tank manufacturer’s
instructions
Table 1, Vacuum Integrity Test Results
47–06 CNG Fuel System
Inspection
WARNING
Natural gas is highly flammable. See the safety
precautions listed in Chapter 21 of the 108SD and
114SD Driver’s Manual or Group 47 of the 108SD
and 114SD Workshop Manual. Failure to observe
these precautions could lead to the ignition of the
natural gas, which could cause severe bodily in-
jury, death, or property damage.
The following inspections must be performed by a
qualified technician, in accordance with the manufac-
turer’s established inspection criteria.
NOTICE
Do not use a high-pressure washer or steam
cleaner on natural gas fuel system plumbing com-
ponents, as this can introduce moisture and con-
taminants into the threads of the fittings and dam-
age the sealants.
Gas detection sensors are located on the cab
overhead console and in the engine compartment
Fuel47
108SD and 114SD Maintenance Manual, May 201847/10
To Next Page
Loading...
