Delphi EFI System: Troubleshooting and Maintenance

[SpudRider]

Electronic fuel injection has seven basic advantages.

1. Improved Fuel Mileage of 10% to 15%
2. Improved starting and cold engine performance without engine warm-up
3. Improved acceleration and smoother throttle performance
4. ECU protects engine components while operating at high engine temperatures and rpms
5. Improved engine performance with varying temperatures and elevations
6. ECU provides diagnostic trouble codes to facilitate troubleshooting of engine problems
7. Cleaner engine emissions

Delphi EFI System Design

Delphi EFI employs 5 sensors to monitor engine performance.

1. Crankshaft Position Sensor
2. Coolant Temperature Sensor
3. Oxygen Sensor
4. Throttle Position Sensor
5. Manifold Air Pressure/Manifold Air Temperature (MAP/MAT) Sensor

Delphi EFI employs the following system components.

1. MT05 Engine Control Unit (ECU)
2. Fuel Pump
3. Multec 3.5 Fuel Injector
4. Idle Speed Control Valve (Idle Stepper Motor)
5. Multec Ignition Coil
6. Fuel Vapor Canister Purge Valve

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Diagnostic Process for Solving Typical Engine Problems

Diagnosis of engine problems is facilitated by using either an engine scan tool, or PCHUD software on a laptop computer.

Compatible Scan Tools for Delphi MT05 ECU

1. Delphi Scan Tool KF90121
2. ED100 Motorcycle Scan Tool

Connect the scan tool/computer to the diagnostic port, and check the system with the engine off. Check the following values.

ENGINE OFF VALUES

Throttle Position

The closed throttle position should read zero. The wide open throttle position should read 100. Throttle position values should smoothly transition from closed throttle, to the wide open throttle position.

Barometric Pressure

With the engine off, the barometric pressure should read the actual atmospheric pressure.

Battery Voltage

The battery voltage should normally read between 12.5 volts to 13.0 volts, with the engine off.

Coolant Temperature

With the engine off, the coolant temperature should read the value of the ambient air temperature. If the reading is different, recheck the reading after changing the coolant temperature sensor.

Intake Air Temperature

With the engine off, the intake air temperature should read the value of the ambient air temperature. If the reading is different, recheck the reading after changing the MAP/MAT sensor.

Desired Motor Step

With the engine off, the desired motor step should read 135. Otherwise, turn off the engine for 15 seconds, and recheck the value. If the value is still incorrect, recheck the value after changing the idle stepper motor.

Current Fault Code

The current fault code should be zero.

Historic Fault Code

The historic fault code should be zero.

Otherwise, clear the fault codes. If a fault code reappears after clearing the fault codes, fix the problem, or change the faulty component. Then recheck the fault codes.

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Verify Proper Engine Operation

Start the engine and check the following values. Engine rpms should increase, and decrease with throttle movement. After coolant temperature reaches 50 degrees Celsius, the engine should idle smoothly at 1600 rpm, without dying.

While riding, the transmission should shift smoothly, and the top speed should meet, or exceed 75 mph. When slowing to a stop, release the throttle, and engage the clutch. The engine rpms should decrease smoothly, and the engine should not stall.

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DIAGNOSING TYPICAL ENGINE PROBLEMS

Insufficient Fuel Supply

Turn the engine off for 15 seconds. Turn on the ignition, and listen for the fuel pump to build pressure in the fuel system.

Remove the fuel injector from the throttle body, and press the starter button. The injector should spray fuel.

Turn off the ignition. Connect a fuel pressure meter to the fuel pump. Turn on the ignition. The meter should read a fuel pressure of 36 psi. If the pressure deviates more than 3 psi, either high or low, replace the fuel pump.

Ignition Problems

Disconnect the wiring plug from the fuel injector. Pull the spark plug wire, and verify spark from the plug wire to the spark plug.

Engine Stalling While Decelerating

Check the battery voltage. Check electrical connections to the MAP/MAT sensor, idle stepper motor, and throttle position sensor. Verify the emission canister purge valve is functioning correctly. Check both of the purge valve hoses for leaks. Check the intake manifold and throttle body for air leaks.

Connect the EFI scan tool/computer, and check for diagnostic trouble codes (DTC).

Check the valve lash.

Clean the throttle body and idle stepper motor with brake cleaner. Clean the MAP/MAT sensor.

Poor Acceleration

Check the fuel filter. If the fuel filter is blocked, replace it.

Turn off the ignition. Connect a fuel pressure meter to the fuel pump. Turn on the ignition. The meter should read a fuel pressure of 36 psi. If the pressure deviates more than 3 psi, replace the fuel pump.

Verify the exhaust system is not blocked.

Clean the MAP/MAT sensor, and check its electrical connector.

Connect the EFI scan tool/computer, and check for diagnostic trouble codes (DTC).
Check the throttle position sensor (0-100 values) and its electrical connector.
Check the O2 Voltage while the engine is idling (100mv – 800mv values), and the electrical connector for the oxygen sensor.

If either sensor is bad, replace the sensor.

Poor Fuel Mileage

Connect the EFI scan tool/computer, and check for diagnostic trouble codes (DTC).
Check the throttle position sensor (0-100 values) and its electrical connector.
Check the O2 Voltage while the engine is idling (100mv – 800mv values), and the electrical connector for the oxygen sensor.

Check the coolant temperature sensor, and the MAP/MAT sensor.

If any sensor is bad, replace the sensor.

Check the fuel injector system for leaks.

Check the emissions carbon canister for blockage, and check the canister purge valve.

Inspect, and clean the air filter. Check the valve lash.

Difficulty Starting the Engine

Inspect the valve lash.

Check the fuel filter. If the fuel filter is blocked, replace it.

Turn off the ignition. Connect a fuel pressure meter to the fuel pump. Turn on the ignition. The meter should read a fuel pressure of 36 psi. If the pressure deviates more than 3 psi, replace the fuel pump.

Clean the fuel injector.

Disconnect the wiring plug from the fuel injector. Pull the spark plug wire, and verify spark from the plug wire to the spark plug. In necessary, change the spark plug.

Clean the throttle valve body with brake cleaner.

High Idle Speed, High RPMS While Shifting or Disengaging Clutch

Connect the EFI scan tool/computer, and check for diagnostic trouble codes (DTC).

Inspect the throttle body and throttle cable.

Electrical System Problems

Check the battery voltage (12.5 V) and connections.

Turn on the ignition key, and verify the fuel pump is operating.

If the electrical system is not activated, check the ignition switch, engine kill switch, and clutch safety switch.

Check all electrical connections and fuses.

Note: Whenever checking for sufficient spark, always disconnect the electrical connector from the fuel injector. Always turn off the ignition before removing any parts from the electrical system.

[SpudRider]

Rebooting the ECU

Perform the following steps to reboot the ECU.

1. Turn off the ignition for 15 seconds.
2. Turn the ignition on/off for 5 cycles. Make sure each cycle lasts about ½ second, verifying the start of the fuel pump for each cycle. If the fuel pump doesn't start during any cycle, begin the entire reboot procedure from the beginning.
3. Turn off the ignition for 15 seconds.

[SpudRider]

The following video was produced by Zongshen, and it is the source for much of the text in this thread.

[SpudRider]

Using the Digital Dashboard to Decipher EFI Trouble Codes

In addition to the diagnostic scan tools, you can use the engine warning light of the Siemens dashboard to diagnose EFI problems. The digital dashboard receives signals from the MT05 ECU, and the engine warning light will flash a diagnostic trouble code (DTC) if the ignition key is switched on/off for three cycles.

When you turn on the ignition, the engine warning light will illuminate, which indicates the EFI system is operational. After the engine is started, the engine warning light will extinguish if the EFI system is working properly. However, if the engine warning light remains illuminated, it indicates the EFI system is not working properly, and there is a system component failure.

Deciphering Diagnostic Trouble Codes

To read the diagnostic trouble code (DTC), open and close the ignition key three times in rapid succession, as follows: open/close—open/close—open. At this point the engine warning light will flash a DTC which indicates the fault in the EFI system. Refer to the fault code table below to identify the corresponding problem.

The engine warning light will emit a sequence of flashing lights. If the light flashes 10 times, the translated number is 0. If the light flashes one time, the translated number is 1, et cetera. For example, if the MAP/MAT sensor is disconnected, or the connector is shorted to ground, the engine warning light will flash in the following manner.

The engine warning light will flash 10 times: The first number of the DTC is 0

After an interval of 1.2 seconds, the engine warning light will flash 1 time: The second number of the DTC is 1

After an interval of 1.2 seconds, the engine warning light will flash 10 times: The third number of the DTC is 0

After an interval of 1.2 seconds, the engine warning light will flash 7 times: The fourth number of the DTC is 7


The resulting DTC is P0107. Referring to the chart below, we see this error code indicates a problem with the MAP/MAT sensor.

If there are other fault codes, the engine warning light will flash the next code in 3.2 seconds after finishing P0107. After all existing fault codes are flashed, the engine warning light will repeat the fault codes, in sequence, until the ignition key is turned off.

[SpudRider]

After EFI problems are resolved, the engine fault codes will remain in ECU memory for about a week, after which they will be automatically erased. However, if you wish to erase the fault codes sooner, you can reboot the ECU following the steps outlined in post #5 of this thread. You can also erase the fault codes using either of the following, diagnostic scan tools.

1. Delphi Scan Tool KF90121
2. ED100 Motorcycle Scan Tool

[SpudRider]

Many Yamaha motorcycles also employ electronic fuel injection. Although the Yamaha EFI systems are different from the Delphi EFI system, one can learn a lot about EFI operation by watching the following Yamaha video.