Propane Autogas
Engine Mechanical and Fuel
Components Service Manual

DSM.0052 Ver. 1.0
May 27, 2022
PRINTED AND DOWNLOADED COPIES ARE UNCONTROLLED

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

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Page 2 of 117

Preface
This manual is designed as a support document for trained technicians in the maintenance and repair procedures
of the 488LPI™ propane autogas engine and fuel system 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.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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Table of Contents
Preface
Acronyms and Application Codes
Safety
Warning and Signal Words Used in this Manual
Qualified Personnel
Inspection and Repair Procedures
Air Compressor Replacement
Air Compressor Belt Replacement
Air Compressor Bracket Replacement
Air Conditioning Compressor Removal
Air Intake Tube Replacement
Alternator Removal
Belt Tensioner Replacement
Block Heater Replacement
Camshaft Inspection and Replacement
Crankshaft Front Oil Seal Replacement
Crankshaft Inspection
Crankshaft Rear Oil Seal Replacement
Cylinder Head Inspection and Replacement
Dual Air Conditioning (A/C) Accessory Bracket Replacement
Engine Front Cover and Crankshaft Front Oil Seal Replacement
Engine Removal and Replacement
Exhaust Backpressure Test
Exhaust Manifold Inspection and Replacement
Flexplate and Transmission Adaptor Replacement
Front End Accessory Drive Components Replacement incl. Tensioner / Pulley
Front Engine Mount Replacement
Fuel Distribution Block Replacement
Fuel Injector Replacement
Fuel Injector Tube Replacement
Fuel Pressure Test Procedure
Fuel Rail Fittings Replacement
Fuel Rail Replacement
Fuel Rail Supply and Fuel Return Line Replacement
Fuel System Pressurization Procedure
Harmonic Damper Replacement
Lower Intake Manifold Replacement
Main Front End Accessory Drive Bracket Replacement
Oil Pan Replacement
Oil Pump Drive Inspection and Replacement
Oil Pump Replacement
DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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Power Steering Pump Pulley Replacement
Pushrod Inspection and Replacement
Roller Rocker Arm Replacement
Roller Rocker Arm Valve Lash Adjustment
Single Air Conditioning (A/C) Accessory Bracket Replacement
Thermostat Replacement
Throttle Body Replacement
Timing Chain and Sprocket Replacement
Upper Intake Manifold Replacement
Valve Cover and Gasket Replacement
Valve Lifter Replacement
Water Pump Replacement
References
Engine Mechanical Torque and Clearance Specifications
Front End Accessory Drive (FEAD) Torque Specifications

Acronyms and Application Codes
A

air brakes

A/C

air conditioning

CKP

crankshaft position sensor

CMP

camshaft position sensor

D

Dual air conditioning

ECM

engine control module

ETC

electronic throttle control sensor

ECT

engine coolant temperature sensor

EVAP

evaporative emissions

FEAD

front end accessory drive

FPT

fuel pressure/temperature sensor

LPG

liquid propane gas

LPI

Liquid Propane Injection

MAP

manifold absolute pressure sensor

MAF

mass air flow sensor

N

No air conditioning

NFPA
S

National Fire Protection Association
single air conditioning

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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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.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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Air Compressor Belt Replacement
REMOVAL PROCEDURE

1

1. Secure vehicle and verify engine is off
and cool.
2. Insert a 1/2-in drive breaker bar into
square socket (1) on Belt Tensioner (2)
to relieve tension on Main Accessory
Drive Belt. Figure 1
3. Remove Main Accessory Drive Belt
(not shown).
4. Use Stretch Belt Installation Tool
(Figure 3) to carefully slip Air
Compressor Belt (6) off Air
Compressor Pulley (4). Figure 2

2
Figure 1:
Belt Tensioner (2) and Drive Socket (1)

INSTALLATION PROCEDURE

4

1. Route Air Compressor Belt (6) around
crankshaft Harmonic Damper Pulley
(5).

2.
3.

4.
5.

Harmonic Damper Pulley is the fourgroove, smaller diameter pulley,
closest to engine block. Figure 2
Route Air Compressor Belt (6)
between Idler Pulleys at location (3).
Figure 2
Use Stretch Belt Installation Tool
(Figure 3) to install Air Compressor
Belt (6) on Air Compressor Pulley (4).
Figure 2
Install Main Accessory Drive Belt.
Refer to OEM service manual for
procedure and proper routing.
Verify proper operation.

DSM.0052 Ver. 1.0 05/27/2022

6

5

3

Figure 2:
Air Compressor Belt (6) routing: Harmonic
Damper Pulley (5); between Idler Pulleys at
location (3); Air Compressor Pulley (4)

Figure 3:
Stretch Belt Installation Tool

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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Air Compressor Bracket Replacement
REMOVAL PROCEDURE

1

1. Secure vehicle; verify engine is off and cool.
2. Remove Air Compressor (not shown). Refer
to Air Compressor Replacement.
3. Disconnect Oil Drain Line (3). Figure 1

4.
5.
6.

7.

Collect any excess oil for reuse or
proper disposal.
Remove Air Compressor Coolant Line
Retaining Clip Bolt (4). Figure 1
Remove lower Idler Pulley Bolt (5) and set
lower Idler Pulley (6) aside. Figures 1 & 2
Remove two (2) Air Compressor Bracket
Retaining Bolts (2) from face of Main
Accessory Drive Bracket and one (1) Bolt
(2) from below Air Compressor Bracket.
Figures 1 & 2
Remove Air Compressor Bracket (1)
from Main Accessory Drive Bracket (7).
Figure 2

2

4
5

3

Figure 1:
Air Compressor Bracket (1), Retaining Bolts (2),
Oil Drain Line (3), Idler Pulley Bolt (5),
Coolant Line Retaining Clip Bolt (4)

Store Air Compressor to Bracket Alignment
Pins (not shown) for reuse.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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INSTALLATION PROCEDURE
1. Install Air Compressor Bracket (1) on Main
Accessory Drive Bracket (7) using Air
Compressor Bracket Retaining Bolts (2).
7
Figure 2
6
2. Torque Air Compressor Bracket Retaining
Bolts (2). Refer to Front End Accessory Drive
2
(FEAD) Torque Specifications. Figure 2
3. Install Idler Pulley (6) with Bolt (5). Figure 2
4. Torque Idler Pulley Bolt (5). Refer to Front
5
1
2
End Accessory Drive (FEAD) Torque
Specifications. Figure 2
5. Connect Oil Drain Line (3). Figure 1
Figure 2:
6. Install Coolant Line Retaining Clip Bolt (4).
Main Accessory Drive Bracket (7),
Figure 1
Air Compressor Bracket (1),
Air Compressor Bracket Retaining Bolts (2),
7. Install Air Compressor. Refer to Air
Idler Pulley (6), Idler Pulley Bolt (5)
Compressor Replacement.
8.

Check engine oil level; refer to
488LPI™ Owner Manual for
specification and procedure.
9. Verify proper operation.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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Air Compressor Replacement
REMOVAL PROCEDURE

Clean all hose and pipe connections prior to
servicing to prevent debris from entering
the coolant or oiling passages.
1. Secure vehicle and verify engine is off
and has had time to cool.
2.

3.
4.
5.

6.
7.
8.

1

Carefully relieve engine cooling
system pressure by slowly
loosening Coolant Reservoir
Pressure Cap.
Partially drain coolant from radiator.
Follow OEM procedure.
Drain all air tanks. Refer to OEM Air
Brake Reservoir Service.
Insert a 1/2-in drive breaker bar into
square socket (1) on Tensioner (2) to
relieve tension on Main Accessory
Drive Belt. Figure 1
Remove Main Accessory Drive Belt.
Remove Air Compressor Belt. Refer to
Air Compressor Belt Replacement.
Disconnect Air Inlet and Air Discharge
Hoses from Air Compressor (7) ports
(3, 4). Figure 3

2
Figure 1:
Belt Tensioner (2) and Drive Socket (1)

6

4

3

5

7

8
Collect any coolant from Air
Compressor cylinder head for reuse
or proper disposal.
9. Disconnect Water Inlet and Outlet
Hoses from Air Compressor (7) ports
(5, 6). Figure 3

9
Figure 2:
Air Compressor (7) port locations:
Air Inlet (3), Air Discharge (4),
Water Inlet (5), Water Outlet (6);
Pulley (9), Pulley Castle Nut (8)

Collect any coolant from Air
Compressor cylinder head for reuse
or proper disposal.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

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10. Disconnect Oil Supply Line (not
shown) at rear of Air Compressor.
11. Remove Air Compressor Pulley Castle
Nut (8). Figure 3
12. Use a special tool to remove Air
Compressor Pulley (9) Figure 3
If pulley is bent during this process,
replace the pulley with a new part.
13. Remove four (4) Air Compressor
Retaining Bolts (10) from Air
Compressor Bracket (not shown).
Figure 3.
14. Remove Air Compressor from vehicle
taking care not to misplace Air
Compressor Bracket Alignment Pins
(11). Figure 3
15. Discard used Air Compressor Base
Gasket (12). Figure 3

10

7
12
11
Figure 3:
Air Compressor (7), Retaining Bolts (10),
Bracket Alignment Pins (11),
Air Compressor Gasket (12)

INSTALLATION PROCEDURE
1. Verify Air Compressor Bracket
alignment pins (11) are in place.
Figure 3
2. Install new Air Compressor base
gasket (12) on Air Compressor bracket
(not shown). Figure 3
3. Install Air Compressor on Base Gasket
(12) and tighten four (4) Air
Compressor Retaining Bolts (10) in a
cross pattern. Figure 4. Refer to Front
End Accessory Drive Torque
Specifications.
4. Press Air Compressor Pulley (9) on Air
Compressor (7). Figure 2
Verify Pulley Keyway is properly
aligned.
5. Torque Air Compressor Pulley
Retaining Nut (8). Figure 2. Refer to
Front End Accessory Drive Torque
Specifications.

DSM.0052 Ver. 1.0 05/27/2022

488LPI Propane Autogas Engine Mechanical
and Fuel Components Service Manual

Figure 4:
Air Compressor Retaining Bolt
Tightening Sequence

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6. Install Water Inlet and Outlet Hoses on
Air Compressor (7) at locations (5) and
(6) and tighten clamps. Figure 2
7. Install Air Inlet and Discharge Hoses
on Air Compressor (7) at locations (3)
and (4) and tighten clamps. Figure 2
8. Connect Oil Supply Line (not shown) to
Air Compressor. Refer to Front End
Accessory Drive (FEAD) Torque
Specifications.