could increase or decrease depending on the cleanli-
ness of the fill station fueling system.
1. Shut down the engine and apply the parking
brake.
2. Close the CNG fuel cylinder shutoff valves.
3. Start the engine and let it idle until the fuel lines
are empty and the engine stops. The gauges on
the fuel panel should now read at or near 0 psi.
4. Close the manual fuel shutoff valve on the fuel
panel.
5. Remove the two capscrews that secure the ac-
cess cover to the fill panel, then remove the ac-
cess cover. See
Fig. 14. Save the capscrews for
reinstallation.
6. Slowly open the bleed valve on the manifold to
relieve remaining fuel pressure within the sys-
tem. See
Fig. 15.
IMPORTANT: Some pressure may remain in the
fuel system between the solenoid valve and the
engine. Use caution when loosening fittings, as
a small amount of gas may leak out.
7. Put a clean receptacle under the filter assembly.
Using a 1-1/4-inch wrench, unscrew the filter
bowl from the filter housing.
8. Remove and discard the filter element.
9. Install a new filter element in the filter housing.
10. Inspect the O-ring on the filter housing for dam-
age or cracks. If necessary, replace the O-ring.
11. Install the filter bowl on the filter housing. Tighten
90 lbf·ft (122 N·m).
12. Close the bleed valve on the manifold and open
the manual fuel shutoff valve on the fuel panel.
13. Open the fuel cylinder shutoff valves.
14. Using a methane detector, leak test all fuel sys-
tem components between the fuel cylinders and
the solenoid valve. A bubble solution can be
used to pinpoint the exact location of leaks.
Repair or replace any leaking components.
H
I
G
H
PR
E
S
S
U
R
E
PR
E
S
S
U
R
E
L
O
W
CYLINDERS
INSPECT CYLINDERS
EVERY 36 MONTHS
OR 36000 MILES
WHICHEVER OCCURS FIRST
NATURAL
GAS
VEHICLE
110 PSIG
ON
M
A
N
U
A
L
S
H
U
T
O
F
F
V
A
L
V
E
OPEN VALVE
SLOWLY
3600 PSIG MAX.
SERVICE PRESSURE
REGULATOR
FILTER
INSPECT PRESSURE
RELIEF DEVICE
EVERY 2000 MILES
DRAIN HOUSING
EVERY 1500 MILES
REPLACE ELEMENT
EVERY 3000 MILES
1
2
3
4
04/30/2010 f470556
1. High Pressure Gauge
2. Low Pressure Gauge
3. Manual Fuel Shutoff Valve
4. Fuel Fill Port and Dust Cap
Fig. 12, CNG Fuel Panel
04/22/2010 f470554
1
2
3
4
5
7
8
6
1. Fuel Cylinder Storage
Box
2. Fuel Cylinder Shutoff
Valves (qty 5)
3. High-Pressure Gauge
4. Low-Pressure Gauge
5. Fuel Fill Port
6. Dust Cap
7. Manual Shutoff Valve
8. Fuel Panel Access
Door
Fig. 13, CNG Fuel Cylinder Storage Box (5-cylinder
system shown)
Fuel47
108SD and 114SD Maintenance Manual, May 201847/12
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