Propane Autogas
Fuel Storage and EVAP System
Service Manual

DSM.0054 Ver. 1.0
May 27, 2022
PRINTED AND DOWNLOADED COPIES ARE UNCONTROLLED

Hexagon Agility Inc. Copyright ©2022. All Rights Reserved.

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

Page 2 of 35

Preface
This manual is designed as a support document for trained technicians in the maintenance, inspection, and
service of the 488LPI™ propane autogas fuel storage and evaporative (EVAP) emissions systems provided by
Hexagon Agility®.
No attempt shall be made to install, maintain, or repair this product until this manual and all referenced supporting
documentation have been read and fully understood.
Original Equipment Manufacturer (OEM) parts not serviced by Hexagon Agility® may be obtained by contacting
Freightliner Custom Chassis Corporation or Thomas Built Buses.
Fuel system warranty or non-warranty product support may be obtained by calling or emailing Hexagon Agility®
Customer Care and Technical Services (CCTS).
Please provide your name, phone number, email address, and complete vehicle information: VIN, year,
make, model, mileage, unit number, vehicle owner, and current vehicle location. A service advisor will
contact you to arrange vehicle repair or ship a part.

®

All parts must adhere to the accepted standards and ratings as specified by Hexagon Agility . Use of
®
any part that is not approved by Hexagon Agility is not recommended and may compromise the integrity
and safety of the system.

Do not remove components from original packaging until necessary. Any components that are to be
reinstalled must be thoroughly cleaned, inspected, and stored in a satisfactory manner until
reinstallation.

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

Page 3 of 35

Table of Contents
Preface
Acronyms
Safety
Warning and Signal Words Used in this Manual
Qualified Personnel
Maintenance, Inspection, and Repair Procedures
Fuel Storage System
Fuel Filter Replacement
Fuel Line Drain Procedure
Fuel Pump Replacement
Fuel System Leak Detection Procedure
Fuel Tank Drain Procedure
Fuel Tank Pass Through Wiring Replacement
Evaporative (EVAP) Emissions System
EVAP Emissions System Overview & Schematic
EVAP Line and Tube Replacement
EVAP Pump Replacement
EVAP System Inspection

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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Acronyms
AHJ

authority having jurisdiction

EVAP

evaporative emissions

LPG

liquid propane gas

LPI

Liquid Propane Injection

NFPA

National Fire Protection Association

Safety
Hexagon Agility® provides safety guidelines to ensure the safety of personnel servicing and / or operating liquid
propane gas 1 (LPG) equipment. All personnel involved must adhere to industry standards including NFPA 58,
specialized training, and all federal, state, and municipal laws and regulations.
Hexagon Agility® minimizes potential hazards through state-of-the art design and testing practices. Always
observe the procedures and recommendations of this manual.
Due to the presence of high-pressure and flammable fuel, LPG fuel systems are a form of hazardous energy
storage.

Warning and Signal Words Used in this Manual
WARNING indicates a hazardous situation which, if not avoided, could result in death
or serious injury.
CAUTION indicates a hazardous situation which, if not avoided, could result in minor or
moderate injury.
NOTICE is used to address practices not related to physical injury, such as best
practices or tips to help an operation or procedure go smoothly and prevent equipment
damage.

Critical
Characteristic

Product feature directly affects:
 Safety of vehicle users, people nearby and maintenance personnel, or
 Regulatory compliance.

Qualified Personnel
LPG systems must be maintained and inspected exclusively by trained personnel with qualifications in
accordance with the applicable codes.
Individuals involved in any aspect of LPG fuel system maintenance, emergency response, servicing or
testing must be properly trained. Individuals who are not trained are not permitted to service, maintain,
test, or inspect a system.

1

LPG used for automotive applications is often referred to as “propane autogas.”
DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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Fuel Filter Replacement
DESCRIPTION AND OPERATION
Two Fuel Filters—a “Fill Filter” mounted in the Fuel Fill Line and an “Inline Filter” positioned in the
Fuel Tank to Engine Lines —remove moisture and other impurities from the 488LPI™ Fuel
Storage System.
Fuel Filters are retained using two mounting methods depending on application:
A. Freightliner Custom Chassis Corporation S2G
 Fill Filter secured using a block clamp bolted to a bracket affixed to the inner rear of
the Fuel Tank protective “cage” structure on the passenger side frame rail. Figure 1
 Inline Filter secured using P-clamps bolted to a bracket affixed to the inner front of the
Fuel Tank cage. Figure 1
A
B

5

Figure 1:
(5) S2G Propane Fuel Tank, (A) Inline Filter (B) Fill Filter.
NOTE: Passenger side frame rail, mounting plates, and clamps not shown.

B. Thomas Built Buses C2 Propane
 Fill Filter secured using a block clamp bolted to a plate affixed to chassis frame
crossmember at rear of Fuel Tank. Figure 2
 Inline Filter secured using P-clamps bolted to a plate at bottom middle of Fuel Tank.
Figure 2

4

B

FRONT

A

Figure 2:
(4) C2 Propane Fuel Tank, (A) Inline Filter (B) Fill Filter.
NOTE: Chassis frame crossmember, mounting plate and clamps not shown.

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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Fuel Line pressure can exceed 250 psi (17 bar). Exercise caution when performing fuel
system service.
REMOVAL PROCEDURE

FLOW

3

2

1

FLOW

1. Secure vehicle outdoors in a safe location.
2.

Bleed Fuel Lines per NFPA 58 and any
organizational or AHJ regulations.
3. Remove Fuel Lines from Fuel Filter (1) inlet
port (2) and outlet port (3). Figure 3
4. Remove Fuel Filter (1) from mount:
a. C2 Propane Inline Filter
 Remove three fasteners (10) securing
Fuel Filter Mounting Plate (9) to Fuel
Tank assembly to access P-clamps.
Figure 4
 Loosen P-clamps (6) to remove Fuel
Filter (1). Figure 5
b. C2 Propane Fill Filter
 Remove two fasteners (not shown)
securing Block Clamp to OEM plate
(not shown) at chassis crossmember.
Figure 6
 Remove (1) Fuel Filter from (7) Block
Clamp and (8) Isolator. Figure 6
Inspect Isolator for wear. Set intact
Isolator aside for reuse or obtain
replacement for damaged or
missing Isolator from Hexagon
Agility.

Fuel Line

Fuel Line

6

Figure 3:
Fuel Filter (1), inlet port (2), outlet port (3).
NOTE: P-clamps (6)shown.
5

FRONT

9

1

10

Figure 4:
C2 Propane Fuel Tank (5), Inline Fuel Filter (1),
Fuel Filter Mounting Plate (9), fasteners (10)
6

1

FRONT
Figure 5:
C2 Propane Inline Filter (1), P-clamps (6)
7

1
8

Figure 6:
C2 Propane Fill Filter (1), Block Clamp (6),
Isolator (8)

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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c. S2G Inline Filter
 Loosen P-clamps (6) to remove Fuel
Filter (1). Figure 7
d. S2G Fill Filter
 Remove two fasteners securing Block
Clamp to plate (not shown). Figure 8
 Remove (1) Fuel Filter from (7) Block
Clamp and (8) Isolator. Figure 8

6

1

Figure 7:
Fuel Filter (1), (6) P-clamps

Inspect Isolator for wear. Set intact
Isolator aside for reuse or obtain
replacement for damaged or missing
Isolator from Hexagon Agility.

7
1

INSTALLATION PROCEDURE

8

1. Install Fuel Filter in mount as follows:
a. (6) P-clamps Figure 7
b. (7) Block Clamp, (8) Isolator Figure 8
Verify Inline Fuel Filter is installed in the
proper direction as indicated by flow arrow
on the label.
2. C2 Propane Inline Filter ONLY: Install Fuel
Filter Mounting Plate on Fuel Tank.

Figure 8:
Fuel Filter, (8) Block Clamp, (7) Isolator

Torque bolts to 7 ft-lbs (9.5 Nm).
3. Install Fuel Lines on Fuel Filter (1) inlet and
outlet ports (2) and (3). Figure 3
4.

Check for fuel leaks. Refer to Fuel System
Leak Detection Procedure.
5. Verify proper operation.

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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Fuel Line Drain Procedure
DESCRIPTION AND OPERATION
Chassis mounted 488LPI™ Fuel Lines supply liquid propane to the engine and return fuel back
to the Fuel Tank. When performing fuel system repairs and maintenance, it is sometimes
necessary to drain propane from the Fuel Lines.

Fuel Line pressure can exceed 250 psi (17 bar). Exercised caution when performing fuel
system service.
REMOVAL PROCEDURE
1. Secure vehicle outdoors in a safe location.
5

2.

Bleed Fuel Lines per NFPA 58 and any
organizational or AHJ regulations.
3. Remove Fuel Drain Valve Cap (2) from Fuel
Drain Valve (1). Figure 1
4. Connect Fuel Transfer Hose (not shown) to
Fuel Drain Valve (1). Figure 1
5. Connect other end of Fuel Transfer Hose (not
shown) to Fill Receptacle of Fuel Recovery
Tank. Figure 2

3
4
1

6.

Perform Static Fuel Discharge per NFPA 58
and any organizational AHJ regulations.
7. Repeat Step 6 until no fuel pressure remains
in both lines.

2

Figure 1:
Fuel Tank (5), Fuel Drain Valve (1), Fuel Drain
Valve Cap (2), Fuel Return Manual Shutoff Valve
(3), Fill Valve Adaptor 90-degree elbow (4)

Both Fuel Supply and Fuel Return Lines
must be drained to ensure all pressure is
removed from Fuel Rails.
8. Disconnect Fuel Supply Line from Fuel Supply
Manual Shutoff Valve (6) and Fuel Return Line
from Fuel Return Manual Shutoff Valve (7).
Figures 3 & 4
Cover Fuel Line openings to prevent
moisture or FOD intrusion.

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

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INSTALLATION PROCEDURE
1. Install Fuel Supply Line on Fuel
Supply Manual Shutoff Valve (6) and
Fuel Return Line on Fuel Return
Manual Shutoff Valve (7). Refer to
Fuel Line Replacement. Figures 3 & 4
2. Slowly open Fuel Supply and Return
Manual Shutoff Valves (6) & (7) by
turning knobs counterclockwise.
Figures 3 & 4

Figure 2:
Fuel Recovery Tank

3.

Check for fuel leaks. Refer to Fuel
System Leak Detection Procedure.
4. Verify proper operation.

7

6
Figure 3:
Tank Side Fuel Supply Manual Shutoff Valve (6)
and Tank End Fuel Return Manual Shutoff Valve (7)
locations

6

7

Figure 4:
Tank End Fuel Supply Manual Shutoff Valve (7) and
Fuel Return Manual Shutoff Valve (6) locations

DSM.0054 Ver. 1.0 05/27/2022

488LPI Propane Autogas
Fuel Storage and EVAP System

Page 10 of 35

Fuel Pump Replacement
DESCRIPTION AND OPERATION
The 488LPI™ Fuel Pump is specially designed for use on propane fuel systems. The Fuel Pump
is controlled by a relay which is controlled by the Electronic Control Module (ECM) using a ground
side driver. The ECM ground the Fuel Pump Relay which in turn supplies power to the Fuel Pump
and the Fuel Supply Solenoid. The Fuel Pump is powered on during the fuel purge cycle and
anytime the engine is running.
The Fuel Pump provides boost pressure to the fuel system above tank pressure which varies
depending on temperature. Tank pressure is directly proportional to tank temperature, meaning
that when temperature goes up the tank pressure goes up. Normal boost pressure should be at
least 55 psi (3.8 bar) more than tank pressure. Boost pressure is necessary to ensure liquid
propane does not vaporize until it is injected by the Fuel Injectors. Fuel boost pressure readings
less than 55 psi (3.8 bar) above tank pressure must be diagnosed and repaired, as low boost
pressure may lead to poor engine performance and the setting of ECM fault codes. If the Fuel
Pump is deemed defective it should be replaced.

Fuel Line pressure can exceed 250 psi (17 bar); exercise caution when performing fuel
system service.
REMOVAL PROCEDURE
1. Secure vehicle outdoors in a safe location.
2. Bleed Fuel Lines per NFPA 58 and any
organizational or AHJ regulations.
3. Drain Fuel Tank. Refer to Fuel Tank Drain
Procedure.
4. Remove Fuel Tank (8) Access Cover (1)
Retaining Bolts (2). Figure 1
5. Remove Fuel Tank Access Cover (1). Figure 1
6. Remove Fuel Tank Access Cover (1) O-ring (3).
Figure 1
7. Disconnect Fuel Pump Supply Line Quick
Connect Adaptor (7). Figure 2
8. Disconnect Fuel Pump Electrical Connector (6).
Figure 2
9. Remove Fuel Pump Retaining Nuts (5). Figure 2
10. Remove Fuel Pump Assembly from Tank (8)
through Access Opening (4). Figures 1 & 2

DSM.0054 Ver. 1.0 05/27/2022

4

3
1

8

2

Figure 1:
Fuel Tank (8), Access Cover (1), Access Cover
Retaining Bolts (2), Access Cover O-ring (3),
Access Opening (4)

488LPI Propane Autogas
Fuel Storage and EVAP System

Page 11 of 35

INSTALLATION PROCEDURE
1. Install new Fuel Pump (10) into Fuel Tank
(8) through Access Opening (4). Figures 1
&2
2. Connect Fuel Pump Electrical Connector
(6). Figure 2
3. Install two (2) Fuel Pump Retaining Nuts
(5). Refer to Fuel System Torque and
Tightening Specifications.
4. Connect Fuel Pump Fuel Supply Line to
Quick Connect Adaptor (7).
Gently pull on Fuel Line to ensure
Quick Connector is seated.
5. Install new Fuel Tank Access Cover O-ring
(3). Figure 1
6. Install Fuel Tank Access Cover (1). Figure
1
7. Install Fuel Tank Access Cover Retaining
Bolts (2).
Tighten Bolts using a star pattern.
Refer to Fuel System Torque and
Tightening Specifications. Figure 1
8. Fill Fuel Tank with propane removed
during Fuel Tank Drain Procedure.
9. Install Fuel Supply and Fuel Return Lines.
Refer to Fuel Line Replacement.

10

8

5
6

7

9
4

Figure 2:
Cutaway of Fuel Tank (8) showing Access
Opening (4), Fuel Pump Retaining Bolts (5),
Fuel Pump Electrical Connector (6), Fuel Supply
Line Quick Connect Adaptor (7); Fuel Supply
Line (9)

10.

Check for leaks with an approved LPG