Snowmobile Fanatics

Triple Heaven

[size=5]EFI Parts[/size=5]
*Keep in mind this is a work in progress, I will continue to update and add as I find information.*

1.Throttle Bodies

-These are individual bodies that are assembled as a unit to control the amount of air entering the engine. Each throttle body controls the air intake for one cylinder using a throttle plate in the throttle body bore. The throttle plates move in response to the movement of the throttle on the handlebars. Adjustment screws on the throttle plate shafts are used to synchronize throttle plate movement so all cylinders perform equally. AKA, equivilent to syncing your carbs.

A throttle position sensor(TPS) is located on the side of the mag side throttle body. The ECU measures the voltage from the TPS to determine the position of the throttle shaft.

2. Fuel Pump
The fuel pump is located on the bulkhead nearest the mag side throttle body. The pump is a roller vane type and uses the fuel it supplies to cool and lubricate itself. There should be a small mesh screen on the inlet of the pump that prevents large contaminants from entering the pump.

3. Fuel Pressure Regulator (Refer to Thottle Body Diagram_Part #2)

-The fuel pump supplies pressurized fuel to the fuel injector at a constant pressure due to the fuel pressure regulator located at the end of the rail. The pressure regulator keep a constant fuel pressure of 36 psi. If the pressure is greater than the 36 psi then the regulator opens and the fuel passes to a fuel return line until the pressure is back to 36 psi. The fuel in the return line travels back to the fuel tank.

There is a vaccuum hose that connects the fuel pressure regulator to throttle body bore and to the adjacent throttle body. Changes in the throttle body vaccum, like WOT, change the regulator setting. Change in the fuel pressure results in a change of air-fuel mixture to gaurd against extreme rich and lean conditions.

4. Electronic Control Unit (Refer to EFI Parts_Part #1)
-The ECU control the injectors and can determine how long they remain open to keep the engine running at optimum performance under all conditions. The ECU uses sensors scattered throughout the sled to determine engine temperature, intake air temperature, and throttle position. The ECU also monitors engine speed through the ignition CDI module. Al barometric pressure sensor helps the engine determine the pressure allowing it to compensate for altitude changes.

The ECU also monitors the working order of the sensors while the sled is running. If the voltage from a sensor isn't correct, the ECU determines that there is a problem and it may enter a "fail-safe" mode that will run the sled extremely rich. Or the ECU can even shut the sled down via a relay which will ground the ignition system. The ECU will also keep the malfunctioning component in it's memory in the form of a trouble code. The ECU will display the code in the form of a blinking LED on the side of the ECU case in a coded sequence of long and short pulses.

5. Throttle Position Sensor(Refer to Throttle Body Diagram_Part #3)
-The TPS senses the position of the throttle shaft which runs through all three throttle bodies and connects all three throttle plates. The TPS is a variable resistance component. As the throttle position changes the sensor changes resistance to reflect this. Then the reading is send back to the ECU.

6. Intake Air Temperature Sensor (Refer to EFI Parts_Part #2)

-Located in the air box the intake air temperature sensor works the same as the TPS in that it is a variable resistance device. As the temperature changes the sensors resistances changes and a voltage is dropped across it. Then the ECU determines the reading based on the drop. The sensor reading allows the ECU to better determine the time the injector should be open.

7. Barometric Pressure Sensor

-The Barometric pressure sensor is located in the ECU box and cannot be repaired or altered. The sensor measures the air pressure, the reading is used to allow the ECU to change the mixture based on altitude.

8. Crankcase Temperature Sensor
-The crankcase temperature sensor is another resistance variable sensor that is located on the top half of the crankcases on the mag side of the motor. This reading is sent to the ECU. Guessing the purpose maybe to prevent damage to the engine if the sensor reading is high, maybe involved with shutoff relay.

9. Coolant Temperature Sensor -The coolant temperature sensor is again a variable resistance sensor. It is located on the underside of the coolant manifold immediately under the coolant cap. Was used on some RXL models, but not all. Used to change the fuel mixtue richer if the sensor indicates a hot condition. It does this to try and cool the engine. May also be involved with preventing damage to the motor by shutting down the sled when it gets beyond a certain point.

10. Fuel Injector -The injectors are operated by a pulse from the ECU. This pulse activates a solenoid which pulls a needle upward and allows the pressurized fuel to flow. This injector is a pintle type.

11. Dropping Resistor
-The resistors drop the pulsing voltage going to the injectors. The resistors are group together in an assembly that sits on a bulkhead near the battery box. Allows 5 volts to pass to injectors at the most.

12. Enrichment Switch
-This switch was used on later RXLs. it is a pushbutton switch located on the console. When pressed it cuts power to the ECU and recylces it as if the engine is being started. This causes more fuel to be added to the mixture upon startup. Recommended use is for high altitude starts.
Conditions

1. Engine is Flooded
Hold the throttle all the way open, this will overide the ECU and not open the injectors. The injectors will begin to open at 800 RPM as the ECU sees this as the motor running.

2. Engine Running Hot
When coolant temperature sensor sees a overheating situation the ECU will keep the injectors open longer to richen the mixture and cool the motor.

1.

RXL Throttle Body

91' RXL EFI

90'-91' RXL Wire Diagram

RXL Cases

[font=Arial][u]1.  Throttle Body Diagram[/u]   [u]2.  EFI Parts Diagram[/u]       [u]3.  Wiring Diagram[/u]       [u]4.  Crank Cases[/u][/font=Arial]

Trouble Shooting Codes:
11. is the throttle position sensor
12. is the crankcase temp sensor
13. is the intake air temp. sensor
*14. is the atmospheric pressure sensor (rxl only)
14. is he water temp sensor
15. is the atmospheric pressure sensor
21. is the flywheel side injector
22. is the center injector (3-cyl)
22. is the Pto side injector (2-cly)
*23. is the Pto side injector (rxl)
31. is low battery voltage
32. is low charging system output
33. is CDI output

(*Note 31, 32, 33 are not used on the RXL.)
(* indicates that this codes is only used on the RXL Model)

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