Snowmobile Arctic Cat (2008 year). Manual - part 75

4-16

Fuel System

(EFI)

This sub-section has been organized for servicing EFI

fuel systems; however, some components may vary

from model to model. The technician should use dis-

cretion and sound judgment when removing/ disas-

sembling and assembling/installing components.

„NOTE: Some illustrations and photographs used
in this section are used for clarity purposes only
and are not designed to depict actual conditions.

Fuel System

(EFI)

Table of Contents

Introduction ........................................................... 4-16
Arctic Cat EFI System ........................................... 4-16
Individual EFI Components ................................... 4-17
Self-Diagnostic EFI System/Codes ....................... 4-19
Testing Individual Components ............................. 4-21
EFI Analyzer/Diagnostic Tool ................................ 4-24
Throttle Body Assembly ........................................ 4-24
Throttle Body Flange............................................. 4-25
Throttle Cable........................................................ 4-25
EFI Component Voltage/Resistance Chart - 

Air Temperature ................................................. 4-27

EFI Component Voltage/Resistance Chart - 

Water Temperature ............................................ 4-28

Troubleshooting Fuel System................................ 4-29

Introduction

The EFI system is lightweight in design and is made

up of a number of components which are explained in

this sub-section. The EFI system eliminates the worry

of changing main jets to compensate for altitude or

temperature. This EFI system will provide quick and

easy starting under all conditions.

When troubleshooting the EFI system, special tools

are required (see page 2 in this section).

Arctic Cat EFI System

The Arctic Cat EFI System operates off a series of

coils located on the stator.

The EFI system is made up of the following compo-

nents.

1. Charge coils (1 and 2) which are located on the

stator provide AC voltage to the ECU/CCU where

AC voltage is converted to DC voltage.

2. A fuel pump coil located on the stator operates the

low voltage, high output fuel pump. At cranking

speed, the high output fuel pump provides enough

fuel to charge the fuel rail.

3. An injector coil located on the stator provides the

injectors with DC voltage for operation through

the ECU.

4. A lighting coil located on the stator plate provides

output to the CCU to operate accessories and the

lighting system.

5. An electrical control unit (ECU) calculates input

from sensors (intake air temperature sensor, cool-

ant temperature sensor, throttle position sensor,

ignition timing sensor, barometric pressure sensor,

and on the 800 cc, a knock sensor) to provide the

engine with the correct fuel mixture and timing for

optimum operation.

EFI FEATURES

1. Automatic compensation for temperature.

2. Automatic compensation for altitude.

3. Optimum throttle response through high pressure

injection.

4. Quick starting in every condition.

5. Improved fuel efficiency with maximum mileage

in every condition.

6. Engine RPM more stable in every condition.

PRECAUTIONS

! WARNING

Whenever working on the fuel system if a fuel hose
is removed from any component, slowly bleed the
pressure from the hose into an absorbent towel
before removing the hose from the component.

! WARNING

 Always tighten fuel hose clamps securely.

4

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0729-325

FLOODED ENGINE

If the engine should become flooded, set the brake

lever lock, compress the throttle lever to the full-open

position, and crank the engine over until it starts and

clears itself. Release the brake lever lock.

FUEL SYSTEM

The EFI fuel system consists of the following compo-

nents.

1. Gas tank

2. Electric high output fuel pump

3. Two pick-up valves with micron screens

4. High-pressure fuel hose

5. Fuel rail

6. Fuel pressure regulator located in the fuel pump

7. Throttle body assembly

8. Injectors

9. ECU

These components are grouped into the fuel handling

system. They work together along with electrical sen-

sors (following list) and the ECU to provide the engine

with a precise fuel mixture for combustion. The sen-

sors are the following.

1. Ignition Timing Sensor

2. Intake Air Temperature Sensor

3. Coolant Temperature Sensor

4. Throttle Position Sensor

5. Barometric Pressure Sensor

6. Knock Sensor (800 cc)

The fuel is first drawn into the electric fuel pump

through two pick-up valves and hoses. The fuel is then

routed through a high-pressure fuel hose to the fuel

rail.

The fuel pressure is maintained specified psi in the

fuel rail by the fuel regulator.

With the fuel pressure maintained at a constant psi, the

ECU evaluates the information it receives from the

electrical sensors and opens the injectors for precise

periods of time (pulse widths) to meet engine

demands.

„NOTE: The entire EFI system depends on all
coils functioning properly on the stator.

Individual EFI 

Components

ECU

The ECU is the brain of the EFI system. It uses sensor

inputs to determine the correct fuel/air ratio for the

engine given the existing conditions of altitude and

temperature.

If any of the sensors should fail while the engine is

running, the ECU will sense a problem and go into a

“fail safe” mode. This is an over-rich condition and

will greatly reduce performance. However, the engine

will be protected from a possible lean condition and

engine damage.

The ECU is equipped with a self-diagnostic system

which utilizes the service icon in the speedometer/

tachometer and remains illuminated when a problem

exists with any of the sensors. The technician can

determine the problem sensor by reading the code

shown on the readout screen and applying it to the

ECU Diagnostic Codes chart (see Self-Diagnostic EFI

System in this section).

„NOTE: There are no repairs that can be made to
the ECU.

If the ECU is not receiving current from one of the

output coils on the stator, that circuit will not operate.

Coils on the stator are the charge coils which operate

the ECU, the injector coil which operates the injectors,

the fuel pump coil which operates the fuel pump, and

the lighting coil/chassis control unit which operates all

accessories and the lighting system.

! CAUTION

Always use resistor-type spark plugs and spark plug
caps. Non-resistor components will cause the ECU
to malfunction.

4-18

INTAKE AIR TEMPERATURE 
SENSOR

The intake air temperature sensor is mounted on the

front of the air-intake silencer. Its purpose is to sense

air temperature entering the air-intake silencer and

engine. The ECU sends current to this sensor, and

(depending on the temperature) the sensor will pass a

certain amount of current through the sensor to

ground. The ECU measures how much current passes

through the sensor to ground. From this measurement,

the ECU determines the air temperature and calculates

the fuel/air mixture ratio. This sensor is very sensitive

to temperature change. Resistance will drop as the

temperature rises.

COOLANT TEMPERATURE SENSOR

The coolant temperature sensor is located on the lower

crankcase. This sensor is very sensitive to temperature

change. The ECU measures the current flow through

the sensor to ground. From this measurement, the ECU

can determine the engine coolant temperature and cal-

culate the correct fuel/air mixture ratio.

„NOTE: If the coolant temperature rises above
80° C (176° F), the temperature sensor starts to
richen the fuel mixture. At this time, the check
engine light will flash constantly. Once the engine
coolant temperature reaches the specified temper-
ature 93° C (200° F), the temperature sensor will
signal the ECU to go into the rich mode to protect
the engine from overheating. At this time, the
check engine light will be constantly on.

THROTTLE POSITION SENSOR

The throttle position sensor, located at the end of the

throttle shaft, is a potentiometer (a potentiometer is,

essentially, a voltage divider). This sensor transforms

the throttle-valve position into output voltage to the

ECU. In addition, the sensor detects the opening or

closing speed of the throttle valve and feeds that rate

of voltage change to the ECU.

„NOTE: The input from the throttle position sen-
sor is one of the main inputs for the ECU calcula-
tion of fuel/air mixture ratio.

IGNITION TIMING SENSOR

This sensor is located inside the magneto case next to

the flywheel, and the recoil starter and the flywheel

must be removed to access the sensor.

This sensor is triggered by a small metal disc precisely

mounted to the flywheel flange. Each time the metal

disc rotates past the sensor, a signal is sent to the ECU.

From this signal, the ECU determines ignition and

injection timing and RPM.

BAROMETRIC PRESSURE SENSOR

This sensor is located inside the ECU and is part of the

ECU unit. Its purpose is to sense atmospheric pressure.

From this information, the ECU determines the correct

fuel/air mixture ratio.

„NOTE: This sensor is not replaceable. If it
should fail, the ECU must be replaced.

FUEL INJECTORS

The fuel injectors are positioned in the top of each

throttle body. O-rings seal the top and bottom of each

injector, and they are held in position by a locking

plate secured to the fuel rail.

The fuel injector is an electromagnetic injection valve

controlled by a signal from the ECU. The coil used in

the injector is a high-pressure resistance type. The

ECU determines the optimum fuel injection time and

duration based on signals from the five sensors.

When voltage is sent to the fuel injector, it energizes

the coil and opens the needle valve, thereby injecting

fuel. Because the fuel pressure (pressure differential

between fuel line and manifold) is kept constant, the

amount of fuel injected is determined by the duration

of time the valve is open.

The injectors are coded with symbols (

Q

-

O

-

V

) and are

color-coded yellow and green. When replacement of a

fuel injector is necessary, the injector must be replaced

with an injector of the same code symbol and color.

FS025A

FUEL PRESSURE REGULATOR

The fuel pressure regulator is located in the fuel pump.

The fuel pressure regulator maintains the fuel pressure

at a constant specified level.

! CAUTION

Do not replace an injector with one of a different
code symbol or color. Severe engine damage may
occur.

4

4-19

FUEL PUMP CIRCUIT

The fuel pump and its circuit are provided with current

from the fuel pump coil on the stator.

For this circuit to function correctly, five components

must be in good working order.

Check the following components before considering

the fuel pump assembly to be defective.

A. Fuel pump coil - see coil test procedure.

B. Emergency stop switch and ignition switch

must be ON and in good working order.

C. Fuel pump - see fuel pump test procedure.

D. Wiring harness and connectors - clean the con-

nectors and test the harness.

E. ECU.

Self-Diagnostic

EFI System/Codes

„NOTE: For testing the 800/1000 cc EFI system,
refer to the EFI Diagnostic System Manual, which
accompanies Laptop Diagnostic Tool and Laptop
Diagnostic Test Kit. 

INTRODUCTION

The Service Icon is controlled by the CCU/ECU and

may illuminate for a number of reasons. The icon

should illuminate each time the engine is started, and it

should go out after a few seconds. If the icon stays illu-

minated while the engine is running, the CCU/ECU is

receiving input that is outside of its established param-

eters.

FZ001D

FZ003B

„NOTE: If the icon illuminates and a code is dis-
played on the readout screen, the ECU is receiving
input that is outside of its established parameters.
Refer to the ECU Diagnostic Codes chart.

* On certain models.

„NOTE: For codes ECU 16 and ECU 18, see Servo-
motor Test in Section 5.

The fuel system and the ignition system remain two

separate systems. In a no-start situation, first deter-

mine if the problem is caused by lack of spark or by a

fuel delivery problem or by an internal engine condi-

tion (low cylinder compression for example).

Once the problem area has been determined, check the

components involved using the Fluke Model 73 Multi-

meter or the EFI Analyzer depending on which test is

being made.

TROUBLESHOOTING INDIVIDUAL 
COMPONENTS

„NOTE: To aid in testing the EFI system, refer to
the EFI Analyzer Usage Manual, which accompa-
nies EFI Analyzer Kit.

ECU Diagnostic Codes

Code

Trouble

ECU 12 Failure in ignition coil.

ECU 16* Incorrect adjustment/failure in APV cable.

ECU 17* Failure in exhaust temperature sensor.

ECU 18* Failure in servomotor.

ECU 2 Failure in injector(s).

ECU 21* Failure in knock sensor.

ECU 23* Fail-safe mode activated in knock control system.

ECU 4 Open or short circuit in barometric pressure sensor.

ECU 5 Open or short circuit in intake air temperature sensor.

ECU 6 Open or short circuit in water temperature sensor.

ECU 7 Open or short circuit in throttle position sensor.