TOYOTA CAMRY 2000 Service Repair Manual

NEW FEATURES Ð 5S-FNE ENGINE 8
FEATURES OF 5S-FNE ENGINE
Features of the 5S-FNE engine are listed below.
Item
Features
Performance
wHigh compression ratio is used.
wHigh lift camshaft is used.
wLow back pressure muffler is used.
Fuel Economy
wHigh compression ratio is used.
wValve spring load has been reduced.
wLow-friction, TiN (titanium nitride) coated valve lifters has been
adopted.
Low Emission
wA fuel injection system containing gas injectors has been adopted.
wBecause the fuel is in the gaseous state, it does not come in contact with
the wall surface, making optimal air-fuel ratio control possible immedi-
ately after the engine has been started.
wPrecision air-fuel ratio feedback control that uses an air-fuel ratio sensor
and a heated oxygen sensor has been adopted.
wTwo catalytic converters designed exclusively for the natural gas engine
have been adopted: the WU-TWC (Warm Up Three-Way Catalytic Con-
verter) and the TWC (Three-Way Catalytic Converter).
Other Features
wHighly rigid pistons have been adopted to accommodate the high com-
pression ratio.
wA CNG (Compressed Natural Gas) pressure regulator that precisely reg-
ulates the CNG has been adopted.
wA large-bore delivery pipe and fuel hose with minimal internal conduit
resistance have been adopted.
wThe electro magnetic fuel shut off valve is added on the delivery pipe.
wA fuel pressure sensor that corrects the fuel injection volume and a fuel
temperature sensor have been provided on the delivery pipe.
wThe starting performance of the engine at low temperatures has been en-
sured by increasing the volume of the airflow of the IAC (Idle Air Con-
trol).
wMaterials that excel in wear resistance have been adopted on the valves
and valve seats for both the intake and exhaust.
wRust-resistant spark plugs have been adopted.
wAluminum lining and carbon fiber have been adopted in the fuel tank.
wFor the fuel gauge, a fuel tank fuel temperature sensor and a fuel pipe fuel
pressure sensor have been adopted.

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NEW FEATURES Ð 5S-FNE ENGINE9
ENGINE PROPER
1. General
The cylinder head and the pistons have been changed for the CNG application.
2. Cylinder Head
Materials that excel in wear resistance have been adopted on the valve seats for both the intake and
exhaust.
The shape of the holes into which the injectors mount has been changed to accommodate the injectors
designed exclusively for the CNG application.
The shape of water jacket around plug has been modified to prevent the deformation.
3. Piston
To achieve a high compression ratio, the shape of the top of the piston has been changed and pin boss
hole with taper has been adopted.
An additional surface treatment has been provided to improve heat resistance.
The material has been changed to increase rigidity.
167CN03
167CN02
5S-FNE Engine 5S-FE Engine

NEW FEATURES Ð 5S-FNE ENGINE10
VALVE MECHANISM
1. Camshaft
To recover the reduction of engine performance, the intake valve timing and the amount of lift of the intake
and exhaust valves have been changed from those of the base 5S-FE engine.

Specifications 
Valve TimingValve Lift mm (in.)
EngineIntakeExhaustIntakeExhaustEngine
OpenCloseOpenCloseIntakeExhaust
5S-FNE35 BTDC385 ABDC455 BBDC35 AT D C7.9 (0.311)8.25 (0.325)
5S-FE435 ABDC7.7 (0.303)7.7 (0.303)
2. Intake and Exhaust Valves
To improve their wear resistance, the intake valves have undergone special heat treatment, and the material
of the exhaust valves has been changed.
The shape of the stem to which the keepers attach has been changed to accommodate the adoption of
the cam with a high lift and of the inner shim type valve adjusting shims.
3. Valve Lifter and Adjusting shims
TiN (titanium nitride) coated valve lifter is used to reduce the friction.
To accommodate the high lift, inner shim type valve adjusting shims are used.
Intake Valve
167CN04
Valve LiftersAdjusting Shims
Exhaust Valve
4. Valve Spring
The valve springs for both the intake and exhaust sides accommodate the adoption of the cam with a high
lift and of the inner shim type valve adjusting shims. In addition, their spring rate has been optimized to
reduce friction.

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NEW FEATURES Ð 5S-FNE ENGINE11
INTAKE AND EXHAUST SYSTEM
1. Throttle Body
The throttle body is basically the same as that of the 5S-FE engine. However, to ensure the starting perfor-
mance at low temperatures, the air passage for the IAC (Idle Air Control) has been increased on the 5S-FNE
engine. The IAC valve is a 1-coil type with a built-in driver.
2. Exhaust Manifold
As in the California specification 5S-FE engine,
the stainless steel exhaust manifold and WU-TWC
(Warm Up Three-Way Catalytic Converter) have
been integrated to improve the warm-up perfor-
mance of TWC, thus reducing exhaust emissions.
However, the 5S-FNE engine uses a catalytic con-
verter that has been designed exclusively for the
CNG application, in which the loading of the noble
metal has been increased.
3. Exhaust Pipe
General
To secure sufficient luggage compartment capacity, the main muffler has been relocated below the rear
seat. Furthermore, the muffler capacity has been increased.
A 2-way exhaust control system has been adopted to improve engine performance and reduce
the exhaust noise.
Similar to the WU-TWC, the TWC (Three-Way Catalytic Converter) has been designed exclusively for
the CNG application, in which the loading of the noble metal has been increased.
Main Muffler
167CN06TWCSub Muffler
p12WU-TWC
167CN05

NEW FEATURES Ð 5S-FNE ENGINE 12
2-Way Exhaust Control System
1) General
A 2-way exhaust control system reduces the back pressure by opening and closing two control valves
that are enclosed in the main muffler, thus varying the exhaust gas passage.
The valves open steplessly in accordance with the operating condition of the engine, thus enabling
a quieter operation at low engine speeds, and reducing back pressure at high engine speeds.
2) Operation
The control valves are closed at low engine speeds because the pressure in the main muffler is low.
Therefore, the exhaust gas flows as indicated by the black arrow below, thus reducing the exhaust noise.
The control valves open at high engine speeds because the exhaust gas pressure increased. Therefore,
the exhaust gas flows as indicated by the white arrow below to reduce the back pressure, thus improving
the engine's power output.
: Low Engine Speed
: High Engine Speed
167CN07
Exhaust Gas
Control Valve
Control Valve

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NEW FEATURES Ð 5S-FNE ENGINE13
FUEL SYSTEM
1. General
The compressed gas [maximum pressure approximately 250 kg/cm2 (3600 psi, 24.8 MPa) @215C (705F)]
from the CNG fuel tank located in the rear section of the vehicle is routed via a fuel filter to the engine
compartment. The pressure of the fuel is then reduced to 8 kg/cm
2 (114 psi, 785 kPa).
A pressure regulator and injectors designed exclusively for CNG application have been adopted.
A fuel pressure sensor and a fuel temperature sensor that are used for the correction of the fuel injection
volume are located on the delivery pipe.
The fuel tank, pressure regulator, and the delivery pipe are provided with shutoff valves that shut off
the fuel when the ignition switch is turned OFF.
In addition, these valves shut off the fuel when the engine stalls, the SRS airbag is deployed, or the
pressure in the main pipe becomes abnormally low.
A fuel temperature sensor for the fuel gauge is mounted on the tank valve assembly, and a fuel pressure
sensor is mounted immediately upstream of the pressure regulator.

Fuel System Diagram 
167CN12
Discharge
Valve
Fuel
Pressure
SensorFuel Temp.
SensorFuel
Pressure
RegulatorFuel Shutoff ValveFuel TankFuel Shutoff Valve
Relief Valve
Inlet Check
Valve
Fuel Temp.
Sensor
Coupler
Tank Valve Assembly
Vent Tube Manual
Shutoff
Valve Fuel
Filter
Fuel
Pressure
Sensor
Fuel Shutoff Valve Injectors
Delivery Pipe

NEW FEATURES Ð 5S-FNE ENGINE 14
2. Fuel Tank
A fuel tank made with carbon fiber and alumi-
num lining has been adopted to prevent weight
increase.
Because the fuel tank expands along with the
increase in the pressure of the compressed gas,
the tank bands contain coil springs to accommo-
date the fluctuation in the perimeter of the tank.
The fuel tank is provided with a tank valve as-
sembly.
3. Tank Valve Assembly
General
The tank valve assembly is mounted on the tank
and consists of a fuel shutoff valve, inlet check
valve, relief valve and two manual cutoff valves.
167CN08
Coil Springs
Tank Valve
AssemblyTank Band
167CN26
Fuel
Temperatur
Sensor
Tank Valve Assembly

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NEW FEATURES Ð 5S-FNE ENGINE15
Fuel Shutoff Valve for Fuel Tank
This valve uses an solenoid valve. The main pipe that supplies compressed gas to the engine is connected
to this valve, which opens when the ignition switch is turned ON. If the engine stalls, this valve automatical-
ly shuts off the fuel even if the ignition switch is turned ON. The valve reopens upon restarting the engine.
Also, this valve shuts off the fuel if the SRS airbag is deployed in a collision or if the pressure in the
main pipe becomes abnormally low.
Inlet Check Valve
Connected to a filler pipe that guides the fuel that fills through the coupler, the inlet check valve shuts
off by the force of a spring and by the pressure of the gas in the tank.
During filling, the pressure of the filling gas opens the inlet check valve.
Relief Valve
A vent tube is connected to this valve.
If the fuel tank is exposed to an abnormally high temperature, this valve opens (by melting) to discharge
the CNG at a predetermined temperature, thus preventing the fuel tank from bursting due to the increase
in gas pressure.
The discharged CNG is guided under the floor through a vent tube and is released outside of the vehicle.
4. Coupler
The coupler allows the fuel to be filled when it is connected with a fuel filling nozzle. The coupler has
a built-in check valve to prevent the CNG from flowing backward.
5. Manual Shutoff Valve
This valve is mounted below the vehicle floor.
When servicing the vehicle, this valve can be manu-
ally turned 90 degrees to shut off the main pipe.
167CN09

NEW FEATURES Ð 5S-FNE ENGINE 16
6. Fuel Filter
Mounted below the vehicle floor, the fuel filter re-
moves any moisture or oil from the fuel.
7. Fuel Pressure Regulator
The fuel pressure regulator regulates the fuel pressure by reducing the pressure of the compressed natural
gas from the fuel tank to the fuel injection pressure, which is 8 km/cm
2 (114 psi, 785 kPa).
Similar to the fuel shutoff valve for the fuel tank, a fuel shutoff valve is provided on the fuel inlet side
of the fuel pressure regulator to shut off the supply of fuel when the engine is stopped or during abnormal
conditions.
An oil separator that traps the moisture and oil in the fuel is provided on the low pressure side.
A built-in relief valve is provided to protect the parts located on the low pressure side.
While the fuel pressure is being reduced by the fuel pressure regulator, the Joule-Thomson effect associat-
ed with the expansion of the gas causes the fuel pressure regulator to be cooled excessively, exerting
unfavorable influence on the rubber parts such as diaphragms and fuel hoses.
Therefore, to raise the gas temperature, a water passage is provided in the fuel pressure regulator to
allow the engine coolant to warm the regulator.
Oil
Separator
Water Passage
Fuel
Shutoff
Valve
Relief Valve
167CN24 167CN25167CN10

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NEW FEATURES Ð 5S-FNE ENGINE17
8. Delivery Pipe
A delivery pipe with a wide passage that enables a large volume of gas to flow responsively has been
adopted to minimize the pressure loss.
A fuel pressure sensor and a fuel temperature sensor that help correct the fuel injection volume are mounted
on the delivery pipe.
Similar to the fuel shutoff valves for the fuel tank and the fuel pressure regulator, a fuel shutoff valve
is provided on the fuel inlet side of the delivery pipe to shut off the supply of fuel when the engine
is stopped or during abnormal conditions.
To discharge the fuel out of the delivery pipe during service, a discharge valve is provided.
Injector
167CN13
Discharge
ValveFuel Pressure Sensor
Fuel Temp. Sensor
Delivery Pipe
CNG
Fuel Shutoff
Valve
9. Injector
For the injection of fuel in the gaseous state, injectors that allow the flow of a large volume of fuel and
provide improved sealing performance have been adopted.
These injectors are actuated by the voltage (150V) that has been increased by the voltage booster circuit
provided in the ECM.
ECM
167CN14
167CN23
Rubber Sheet
12V
+B
Voltage
Booster
Circuit#10+
#10Injector