6
7
8*
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23*
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

QTY

1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1

Description
Fitting, male connector
Fitting, male adapter
Dust cap, rubber, NGV1/defuel receptacle
Receptacle, CNG NGV1/defuel receptacle
Receptacle, CNG transit (fast) fuel fill
Dust cap, rubber, transit fuel fill
Fuel fill manifold, with remote fuel fill port
Fuel fill manifold, standard
Fitting, adapter
Tube, HP fuel, HP filter to regulator
Fitting, straight union
Fitting, 90-degree adjustable elbow
Fitting, adapter, straight
Fitting, JIC, 90-degree elbow, large
Fitting, JIC, 90-degree elbow, small
Fitting, JIC, straight
Defuel valve
Pressure regulator
Supply solenoid valve
Pressure transducer, Manifilter
ASM, Manifilter (HP fuel filter)
1/4-turn manual shutoff valve
Spacer, 1/4-turn manual shutoff valve
High-pressure (HP) fuel filter element
P-clip, 3/8-in., rubber clamp (10 mm)
ASM, Tube, PRV, regulator to vent
Tube, HP fuel, filter to 1/4-turn manual shutoff valve
Tube, HP fuel, filter to HP gauge
Tube, LP fuel, regulator to LP gauge
Tube, HP fuel, needle (defuel) valve to manifold
Cap, PRV vent, heat shrink
Check valve, 6000 psi, CNG, with fittings
Gauge, high-pressure, 0-6000 psi
Gauge, low-pressure, 0-200 psi
Fitting, connector
Bleed valve, Manifilter
Vent stack assembly
Face plate, FMM (NOTE: Face plate shown is for optional Smart Gauge; standard face plate is similar.)
Cover, FMM, rear
Auxiliary remote fill panel (optional)

*Not shown

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3. Fuel System Components and Specifications
3.1. Fuel Specifications

3.3. Fuel Management Module (FMM)

Fuel quality is crucial to maintaining engine
performance characteristics, life expectancy, and
emission standards. CNG fuel must meet or exceed
Cummins CES 20067 requirements.

The FMM is the fuel fill and flow control interface.
Figure a, 9b, and 10. The FMM is accessed by
opening the fill panel access door at the rear
passenger side of the vehicle.
1

2

4

3

5

Failure to meet fuel requirements may result in
poor engine performance and damage that is not
covered under warranty.

3.2. Superstructure

6

Fuel system structures and components are
designed to meet or exceed all safety and vehicle
standards. Systems are shipped as complete units
ready to be bolted on and connected for turn-key
operation.
Figure illustrates a typical 5-cylinder roof mount
configuration.

Figure 9a. FMM face plate components.
(1) 1/4-turn manual shutoff valve, (2) transit (fast) fill receptacle,
(3) high-pressure gauge, (4) defuel receptacle, (5) low-pressure
gauge, (6) Smart Gauge (if equipped).

Additional flow components and connections are
located inside the FMM. Figure 9b

1
2

Figure 8. Typical 5-tank roof mounted CNG storage system.
NOTE: Fuel system with electric solenoid cylinder valves shown;
fuel systems with manual cylinder valves similar.

7

4

5

6

8

3
Figure 9b. FMM components (bottom view):
(1) HP fuel line to cylinders, (2) high-pressure
Manifilter, (3) remote fill panel (optional); (4)
solenoid valve, (5) pressure regulator, (6) regulator
coolant ports, in & out, (7) defuel valve, (8) LP fuel
line connection.

An optional remote fill panel connects to a special
manifold on the rear of the FMM for ease of fueling.
Figure 10

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1

1

3
4
6
5

4

5

2

7
2

8
9

3
Figure 10. Remote fill option components:
(1) tube, remote fill to FMM manifold. (2) dust cap,
(3) transit (fast) fill receptacle,
(4) remote fill bracket, (5) remote fill manifold.

3.4. Filters

3.4.2. Low-Pressure Fuel Filter

3.4.1. High-Pressure Fuel Filter
The high-pressure (HP) coalescing fuel filter
assembly or Manifilter is located downstream of the
manifold and 1/4-turn manual shutoff valve and
upstream of the supply solenoid valve (SSV). The
HP filter purifies fuel by removing moisture and
contaminants. Figure 11
Efficiency: 10 microns
Change Frequency: Every 30,000 miles
(48,000 km)

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Figure 11. Manifilter HP (high-pressure) fuel filter components:
(1) Manifilter housing, (2) filter bowl O-ring, (3) HP filter element
O-ring, (4) HP filter element housing, (5) HP filter element, (6)
element base, (7) Manifilter bowl, (8) drain plug O-ring,
(9) hex head drain plug.

The low-pressure (LP) coalescing fuel filter is
located downstream of the FMM 1/4-turn manual
shutoff valve, Manifilter, and pressure regulator. The
LP filter removes residual contaminants and oil from
the fuel before it enters the engine.
Low-pressure Fuel Filter specs
The LP filter is sealed with a lubricated gasket
and includes a drain cock at the bottom. Figure
12
Operating range: -43°F to +250°F
-42°C to +121°C
Efficiency:
 99.9% for 0.3 micron liquid droplet
 100% for 25 micron particles
Mounting type: Spin-on, 1-1/2-16 UN-2B thread

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3.6. Pressure Regulator

1

Located adjacent to the supply solenoid valve in the
FMM, the pressure regulator is the dividing point
between the high-pressure and low-pressure sides
of the fuel system.

2

The pressure regulator reduces CNG up to 3600 psi
(250 bar) down to a pressure usable by the engine
typically around 125 psi (8.61 bar). Figure 14

3
Figure 12. Low-pressure filter components:
(1) LP filter head; (2) LP filter element, (3) drain cock.

3.5. Supply Solenoid Valve
Located in the FMM between the HP filter and the
pressure regulator, the supply solenoid valve
controls CNG flow. Figure 13
The supply solenoid valve generates heat during
operation and may cause burns on contact with
unprotected skin.

Figure 13. Supply solenoid valve.

3.5.1. Supply Solenoid Principles of Operation
De-energized: The supply solenoid valve acts
directly by utilizing an armature and a pilot as
opposed to a plunger. Pressure from the inlet port
flows through the pilot guide surrounding the
armature, the pressure is then stopped by the pilot
at the orifice.
Energized: The supply solenoid valve operates
using 24V DC from the onboard power supply. The
armature is forced upwards and lifts the pilot from
the seat of the orifice allowing pressure to flow from
the inlet port to the outlet port.

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Figure 14. Pressure regulator.

Pressure regulator specs
Set point: 125 psi (8.61 bar) outlet @ 3600 psi
(250 bar) inlet pressure
PRV: 200 ± 40 psi (13.7 bar ± 2.75 bar) crack
pressure
Max. pressure: 3600 psi (250 bar)
Min. pressure: 250 psi (17.2 bar)
Gas flow rate: 0-110 lb/hr nominal
Coolant temperature range: -40°F to +257°F
-40°C to +125°C

3.7. Cylinders
The five roof mounted cylinders are standard Type 4
CNG cylinders designed, manufactured, inspected,
and qualified in accordance with NGV-2 2007.
Total fuel system water volume is noted on the FMM
face plate.
Cylinder specs
Service pressure: 3600 psi @ 70°F
250 bar @ 21°C
Service life: Refer to cylinder manufacturer
label or marking.

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3.8. Valves

3.8.4. 1/4-Turn Manual Shutoff Valve

3.8.1. Bleed Valve

The 1/4-turn manual shutoff valve located on the
FMM face plate is also known as the “main” or
“emergency” shutoff valve.

Turning a nut to open a bleed valve installed inside
the FMM allows for the release of residual fuel
system pressure for depressurization and defueling
procedures.
The bleed valve (1) enables safe venting of system
pressure and is located on the Manifilter (3). Figure
15
1

3

When in the CLOSED/OFF position, the 1/4-turn
manual shutoff valve prevents the flow of CNG past
its location in the fuel system. Turned the OPEN/ON
position, the 1/4-turn manual shutoff valve permits
fuel to flow from the cylinders to the FMM
components. As its name implies, turning the 1/4turn manual shutoff valve 90-degrees by hand
changes it from OPEN to CLOSED and reversing the
direction of rotation restores it to the OPEN position
for normal operation. Figure 18

2
Figure 15. Bleed valve location.
(1) Bleed valve, (2) nut, (3) Manifilter.

Bleed valve specs

Figure 18. 1/4-turn manual shutoff valve.

Flow coefficient: 0.25
Temperature rating: -4°F to +450°F
-20°C to +232°C
3.8.2. Check Valve
Check valves located downstream the fill
receptacles in the FMM prevent CNG from following
out of the system. Figure 16

1/4-turn manual shutoff valve specs
Temperature rating: -40°C to +93°C
-40°F to +200°F
3.8.5. Manual Cylinder Valve
Each cylinder in 25530000, 25534000, and
25538000 fuel storage systems is equipped with a
manually operated shutoff valve to isolate CNG
contained within from the rest of the fuel system.
Figure 19

Figure 16. Check valve.

3.8.3. Defuel Valve
Located inside the FMM. the defuel valve allows fuel
to be removed from the system via the defuel
receptacle. Figure 17
Figure 19. Manual cylinder valve.
NOTE: 25530000, 25534000, and 25538000 fuel systems only.

Manual cylinder valve specs
Service pressure: 3600 psi (250 bar)
Figure 17. Defuel valve.

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Working temperature: -40°F to +180°F
-40°C to +82°C
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3.8.6. Electric Solenoid Cylinder Valve

3.9. Pressure Relief Devices (PRDs)

Each cylinder in 25531000, 25533000, 25535000,
25536000, and 25537000 fuel storage systems are
equipped with an electrically operated solenoid
shutoff valve to isolate CNG contained within from
the rest of the fuel system.

Remote PRDs

When the vehicle ignition is off, the solenoid cylinder
valve closes. The solenoid cylinder valve is open
during vehicle operation. Figure 20

Each cylinder is equipped with multiple remote
PRDs which connect to the respective cylinder
valves via several live PRD supply tubes. Figures
21a and 21b

Figure 21a. Remote PRD.

Electric solenoid cylinder valve specs

Remote PRD specs
Operating temperature: -40°F to 180°F
-40°C to +82°C
Service pressure: 3626 psi at +59°F
250 bar at 15°C
Working pressure: 4467 psi at 180°F
308 bar at 82°C

Service pressure: 3600 psi (250 bar)

Activation temperature: 230°F / 110°C

Figure 20. Electric solenoid cylinder valve.
NOTE: 25531000, 25533000, 25535000, 25536000,
and 25537000 fuel systems only

Working temperature: -40°F to +185°F
-40°C to +85°C

PRD supply lines are always pressurized when gas
is present in the system.

Figure 21b. Remote PRD locations (circled).
NOTE: Manual cylinder valve system plumbing shown;
electric solenoid cylinder valve system plumbing similar.

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3.10. Fuel Fill and Defuel Receptacles

3.10.2. Remote fuel fill receptacle (optional)

3.10.1. Standard fuel fill & defuel receptacles

Vehicles equipped with an FMM incorporating a
remote fuel fill panel include an additional transit
(fast) fill receptacle matching the specifications
above. Figure 22b

The FMM face plate contains a transit or “fast” fill fuel
receptacle (1) and an NGV1 receptacle (2) used
exclusively for defueling. Figure 22a
3

5

1

2
6

4
Figure 22a. FMM receptacles:
(1) Transit (fast) fill receptacle, (2) defuel receptacle,
(3) transit (fast) fill receptacle dust cap,
(4) defuel receptacle dust cap.

Figure 22b. Optional remote transit fuel fill panel:
(5) transit (fast) fill receptacle,
(6) transit (fast) fill receptacle dust cap.

Dust cap (6) must reinstalled immediately after
receptacle use. Figure 22b

Dust caps (3) and (4) must reinstalled immediately
after receptacle use. Figure 22a

Fuel fill and defuel receptacle specs
Design pressure: 5000 psi (350 bar) max.
Flow rate, transit fill: 5000 SCFM (8043 nm3/hr)
@ 3000 psi (207 bar)
Flow rate, NGV1 defuel: 1500 SCFM
(145 nm3/hr) @
3000 psi (207 bar)
Temperature range: -40°F to +250°F
-40°C to +121°C

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