FRONT

NGV1 fuel fill receptacle
high-pressure
fuel gauge

dust cap

FIGURE 8. Fuel fill panel components.
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2. High-pressure flexible fuel hose. Connects fuel fill panel to high-pressure fuel lines.
FIGURE 7

3. CNG cylinders. The driver side and passenger side CNG cylinders are connected by
a HP fuel cross over tube. FIGURE 7 Refer to Section 2.2.1.
4. 1/4-turn manual shutoff valve. Red handled valve shuts off the flow of fuel from the
cylinders to the engine. The manual shutoff valve is located on the outside of the driver
side chassis rail, just aft of the driver side door. FIGURES 1 and 7

NOTICE.
1/4-turn manual shutoff valve must be in OPEN position for normal operation.
5. High-pressure (HP) fuel filter. Initial trap for any fuel impurities. Located on the inside
of the driver side chassis rail. FIGURE 7
6. Pressure regulator. Reduces CNG from 3600 psi (250 bar) cylinder pressure to 125
psi (8.6 bar) for use by engine. The regulator is located on the inside of the driver side
chassis rail and is equipped with a pressure relief valve. FIGURES 2 and 9

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NOTICE.
Pressure relief valve cap must be in place during operation. If cap is missing,
obtain replacement from Hexagon Agility®.
FRONT

pressure
regulator

frame rail

PRV cap

FIGURE 9. Pressure regulator and pressure relief valve (PRV) cap
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7. Supply solenoid valve. Safety device integral to the pressure regulator and activated
by vehicle ignition. When the ignition is OFF, the supply solenoid valve is closed and
CNG flow to the engine is shut off. When the ignition is ON, the supply solenoid valve
is always open supplying CNG to the engine. FIGURE 3
8. Low-pressure (LP) fuel filter. Secondary trap for any fuel impurities. Located above
the transmission on a frame crossmember. FIGURE 7
9. Low-pressure flexible fuel hose. Connects LP fuel filter to fuel rail assembly. FIGURE
4

10. Fuel rail assembly. Consists of a pair of fuel rails located on either side of the intake
manifold which house fuel injectors to supply low pressure CNG to each engine
cylinder bank. FIGURE 7
11. Fuel injectors. Eight fuel rail mounted fuel injectors supply CNG to each of the eight
engine cylinders.
12. ECU. Electronic control unit (ECU) monitors and directs CNG system operation. The
ECU is located to the left of the steering wheel below the dash.

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2.3.

Engine Starting

The CNG fuel system operates very much like a gasoline system. Use the following
procedure to start the engine:
1. Verify 1/4-turn manual shutoff valve and cylinder manual valves are OPEN. FIGURES 1
and 2

NOTICE.
 Manual shutoff valves must be fully OPEN for proper system operation.
 Excess flow protection requires opening manual shutoff valves slowly; if a click
is heard while opening valve, close valve to reset the excess flow valve.
2. Prime fuel system by cycling ignition to the ON/RUN position. Supply solenoid valve will
open to allow CNG to flow and may be accompanied by an audible click.
3. Wait 15 seconds, then cycle ignition to OFF position.
4. Engage start to crank engine.

NOTICE.
Do not press accelerator pedal prior to or while starting the engine.
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5. If engine does not start, repeat fuel system prime by cycling ignition to ON/RUN position.

NOTICE.
Fuel system prime cycle may need to run 4-5 times after prolonged storage.
6. Allow engine to idle until the system equalizes pressure in the fuel lines and rails.

NOTICE.
If the engine runs rough, do not drive vehicle until engine runs smoothly.

2.4. Vehicle Fueling
NOTICE.
These are general fueling guidelines. Always consult fuel station personnel or
postings for specific fuel dispenser operating instructions and procedures.

2.4.1.

Fuel Properties and Quality

The 6.0L V8 engine is designed to operate on CNG. Clean burning CNG offers reduced
emissions for cleaner air and lower vehicle operating costs.
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.⚠ WARNING.

 Wear approved eye protection when fueling.
 CNG is flammable. Keep sparks and open flames away from CNG. Do not smoke
while fueling vehicle.
 Natural gas is colorless, odorless, and highly flammable. An additive like the
odor of sulfur or rotten eggs is added to CNG to alert to the presence of a gas
leak.

The engine and fuel system require high quality CNG free of dust, oil, or other
contamination.

.⚠ CAUTION.

Use of CNG not meeting SAE J1616 quality standards, or operator failure to properly
cap and clean fueling system connections may decrease engine performance and
damage vital Hexagon Agility® system components or emission controls. Damage to
components resulting from fuel contamination is NOT covered under warranty.

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2.4.2.

Fueling Procedure

.⚠ WARNING.

 Operators must memorize vehicle 1/4-turn manual shutoff valve location and
cylinder manual valve locations. FIGURE 4 Operators untrained or inexperienced
with filling a Hexagon Agility® CNG equipped vehicle should consult a qualified
CNG station operator.
 Never connect fuel fill nozzle to fuel receptacle if O-ring is missing or damaged;
this could cause serious injury or property damage.

Referring to Section 2.3.3., perform the following steps to fuel the vehicle.
1. Turn engine OFF and set parking brake. If required: set wheel chocks.
2. Ensure no open flames or ignition sources are present.
3. Remove dust cap from fuel fill receptacle. FIGURE 8
4. Wipe fuel fill receptacle and fill nozzle. FIGURE 8

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NOTICE.
Check for signs of oil or other contaminants. An oily or dusty condition may
be an indication of poor fuel quality or a station that is not well maintained.
Report unsatisfactory conditions to the station operator.
5. Inspect fuel receptacle O-ring.

.⚠ CAUTION.

Verify O-ring is seated in groove and is not damaged or missing. If a new Oring is required, it may be obtained from Hexagon Agility®. Please refer to
“Support, Service, or Parts” above to order.
Connect fill nozzle to fuel receptacle. FIGURE 8

NOTICE.
If natural gas odor is present, the fuel receptacle O-ring may be worn or
damaged.
6. Turn nozzle valve to “FILL” position and CNG will begin to flow.
7. Continue filling until fuel station dispenser shuts off automatically.
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8. Carefully disconnect filling nozzle from fuel receptacle by rotating fill nozzle valve to
the “VENT” position.

NOTICE.
Fuel receptacle is designed to prevent nozzle from disconnecting while under
pressure.
9. Return fueling nozzle to dispenser.
10. Install dust cap on fuel fill receptacle. FIGURE 8

NOTICE.
Drive Away Protection (DAP) safety interlock requires fuel receptacle dust cap
be in place for engine to start.

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2.4.3.

Fast Fill vs. Slow Fill and Pressure/Temperature Relationship

CNG stations typically fill to a service pressure of 3600 psi (250 bar). During fast filling, it
is normal for gas to heat up as it compresses inside the cylinder(s). On a hot day, pressure
from the filling station will indicate a 100% full cylinder with a system pressure of 3600 psi
(250 bar), but the fuel cylinders may not be filled completely.
For example, when the ambient temperature is 120°F (50°C) in the afternoon, the CNG
dispenser stops at 3600 psi (250 bar) as expected. However, later that evening ambient
temperature drops to 70°F (20°C). As the CNG cools, pressure in the cylinder(s)
decreases. Therefore, instead of having a complete fill of 3600 psi (250 bar) at 120°F,
cylinder pressure is about 3000 psi (207 bar) at 70°F (20°C) or approximately 83% full.
Fueling stations can partially compensate for the heat generated during fast filling, but
generally cannot achieve more than 70% to 80% fill rates. On the other hand, slow filling
results in nearly 100% full, because the CNG can cool during the filling process.

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2.4.4.

Fueling Station Locations

Public and private CNG filling station locations are listed on the following U.S. government
website:

http://www.afdc.energy.gov/locator/stations/

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3. Service and Maintenance
3.1.

Recommended Fluids

The Hexagon Agility® CNG fuel system is a purpose built for medium duty compressed
natural gas operation. Proper maintenance is critical to protect your investment. Poor
maintenance can lead to premature engine wear and fuel system damage. Keep records
to document proper maintenance as outlined in this manual. Failure to properly maintain
fluids can result in costly repairs not covered by warranty.

.⚠ CAUTION.

The use of OEM recommended fluids is critical to proper engine and fuel system
operation and longevity. Failure to use correct fluids can lead to engine and fuel
system damage not covered by warranty.

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3.1.1.

Fuel System Coolant

The Hexagon Agility® pressure regulator is supplied with coolant from the OEM coolant
system.

.⚠ CAUTION.

Follow OEM recommended coolant specifications.

.⚠ CAUTION.

Do not use well water to mix with coolant. Well water contains minerals which
promote cooling system electrolysis; this can cause premature cooling system
damage.

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3.2.

Maintenance Schedule

Hexagon Agility® has established the following maintenance intervals to ensure safe and
reliable engine fuel system operation. For questions regarding engine and fuel system
service and maintenance please refer to the Hexagon Agility® website for the latest contact
information.

Required Engine & Fuel System
Service

Years

Interval*
mi.

km

Replace spark plugs

n/a

50000

80000

Drain and change LP fuel filter element

n/a

5000

8000

Drain and change HP fuel filter element

n/a

7500

12000

Inspect CNG cylinders and mounts**

1

100000

161000

Visually inspect all CNG hoses and lines**

1†

100000

161000

*Vehicles operating in harsh environments may require more comprehensive or more frequent
inspections.
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**Check with Authority Having Jurisdiction for additional cylinder and/or fuel system inspection
schedule requirements. Refer to Section 3.2.1.
†All CNG hoses must be inspected every month or 200 hours.

.⚠ WARNING.

Personal injury or death could result from neglecting to perform the above
recommended services.

.⚠ CAUTION.

Failure to perform the above services according to manufacturer recommendations
may void fuel system warranty.

NOTICE.
The above services must be performed by trained professionals.

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3.2.1.

CNG Fuel Cylinder and Fuel System Inspection Requirements

U.S. Federal Motor Vehicle Safety Standards (FMVSS) Section 304 requires visual CNG
cylinder inspections every 12 months or sooner.

.⚠ CAUTION.

Inspections must be performed by certified inspectors using guidelines from the
fuel cylinder manufacturer in addition to the guidelines listed in this manual.

.⚠ WARNING.

If a CNG-fueled vehicle has been involved in an accident or fire, the system and
cylinders must be inspected by a certified (CGA C-6.4 or other) CNG fuel system
inspector.

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For detailed fuel system inspections, Hexagon Agility® recommends two practical fuel
system inspection schedules–to be selected by the vehicle owner:
1. The common industry recommendation of every 3 years or 36000 miles, whichever
occurs first,
OR
2. After every 1 year or 100,000 miles, whichever occurs first.
In addition, Hexagon Agility® recommends a daily walk-around or pre- and post-trip visual
inspection be performed, regardless of which detailed fuel system inspection schedule is
followed. Refer to Section 2.1. Pre-trip Inspection.

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FCCC MT-45 MT-55 CNG FUEL SYSTEM
P80 - P100 - P120 UPS USER MANUAL

USM.0004 Ver. 2.0
April 7, 2022
Hexagon Agility Inc. Copyright © 2022. All Rights Reserved.