Snowmobile Arctic Cat (2004 year). Manual - part 50

4-35

4

Introduction

The batteryless EFI system is lightweight in design
and is made up of a number of components which are
explained in this sub-section. The batteryless EFI sys-
tem eliminates the worry of battery maintenance or
changing main jets to compensate for altitude or tem-
perature. This EFI system will provide quick and easy
starting under all conditions.

The electrical control unit (ECU) has a self-diagnostic
mode built in. It is a very valuable factor in trouble-
shooting. Once the problem area has been determined
from the trouble code flashed by the LED (light emit-
ting diode) located under the left end of the ECU
(check engine light in the speedometer/tachometer on
“Laydown” engine models), follow the troubleshoot-
ing procedure in this sub-section.

When troubleshooting the batteryless EFI system, spe-
cial tools are required. These special tools are the fol-
lowing.

A. EFI Analyzer (p/n 0644-342)

B. Compression/Pressure Tester Kit (p/n 0644-

366)

C. Fluke Model 73 Multimeter (p/n 0644-191)

D. EFI Analyzer Update Kit (p/n 0637-243)

„

NOTE: Troubleshooting EFI engines with the

APV system should be done with the Arctic Cat
EFI Analyzer (p/n 0644-342). To update your exist-
ing EFI Analyzer, order Kit (p/n 0644-341).

AE131

0644-366

AE114

AE141

Arctic Cat Batteryless 

EFI System

The Arctic Cat Batteryless EFI System operates off a
series of coils located on the stator.

The batteryless EFI system is made up of the follow-
ing components.

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

stator provide AC voltage to operate the CDI unit.
The CDI unit is located within the ECU. The AC
voltage is converted to DC voltage within the
ECU.

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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 operate accessories and the lighting
system.

5. An electrical control unit (ECU) calculates input

from five sensors (intake air temperature sensor,
water temperature sensor, throttle position sensor,
ignition timing sensor, barometric pressure 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

0729-325

OPTIONAL STARTING PROCEDURE 
(STD Models)

1. To start an engine for the first time or after

performing service work on the fuel system, place
the emergency stop switch and the ignition switch
in the ON position. Disconnect the yellow water
temperature sensor lead wire at the ECU. Crank
the engine over 6-8 times with the recoil starter.
With the water temperature sensor lead
disconnected, the fuel system will call for
maximum mixture and the system will charge
faster. After 6-8 brisk pulls on the recoil starter
rope, reconnect the yellow sensor lead. The engine
should start in 2-3 additional pulls. After charging
the fuel system, the engine should start in 3-4 pulls
when cold.

2. Start the engine without compressing the throttle.

When the engine starts for the first time, do not
touch the throttle. It will idle slowly and may stop.
Repeat this procedure until the engine starts and
builds RPM on its own. This may require 3-4
restarts. Once the engine has been started and run,
the next cold start should occur in 2-3 pulls of the
recoil starter rope.

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 *

7. Throttle body assembly

8. Injectors

9. Fuel return hose (600 cc STD)

10. ECU

* On the 600/700 cc “Laydown”/800/900 cc, the regu-
lator is in the fuel pump.

! 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.

! CAUTION

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

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4

These components are grouped into the fuel handling
system. They work together along with five electrical
sensors (following list) and the ECU to provide the
engine with a precise fuel mixture for combustion. The
five sensors are the following.

1. Ignition Timing Sensor

2. Intake Air Temperature Sensor

3. Water Temperature Sensor

4. Throttle Position Sensor

5. Barometric Pressure Sensor

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. If pressure exceeds this
amount, the regulator opens and returns excess fuel to
the gas tank through the fuel return hose (600 cc STD).

With the fuel pressure maintained at a constant psi, the
ECU evaluates the information it receives from the
five electrical sensors and opens the injectors for pre-
cise 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 five
sensor inputs to determine the correct fuel/air ratio for
the engine given the existing conditions of altitude and
temperature.

AO152D

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 light emitting diode
(LED) on standard models or with a check engine light
in the speedometer/tachometer on “Laydown” engine
models, which will flash a series of pulses when a
problem exists with any of the sensors. By observing
the code, the technician can determine the problem
sensor by comparing the code flashed with the trouble
code chart (see Diagnostic Codes in this sub-section).

AO153D

„

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 capacitor charge coil which
operates the CDI within the ECU, the injector coil
which operate the injectors, the fuel pump coil which
operate the fuel pump, and the lighting coil which
operates all accessories and the lighting system. Refer
to the wiring diagram in this sub-section.

AO132D

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INTAKE AIR TEMPERATURE SENSOR

AO135D

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.

WATER TEMPERATURE SENSOR

AO069

The water temperature sensor is located on the bottom
of the thermostat manifold. This sensor is very sensi-
tive to temperature change. The ECU measures the
current flow through the sensor to ground. From this
measurement, the ECU can determine the engine cool-
ant temperature and calculate the correct fuel/air mix-
ture 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 is fully
closed which 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

AO136D

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

0729-627

This sensor is located on the top of the magneto case
near the cylinder on some models. On other models the
sensor is located inside the magneto case next to the
flywheel, and on these models, 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.