LEARNING OUTCOME 3

Fitting Fuel Injection System Components/Devices: Testing

1. Injector Pump Tests (Primarily for Diesel Systems):

Pressure Testing:

• Connect a high-pressure gauge to the injector pump's output.
• Measure the pump's delivery pressure at various engine speeds.
• Compare readings to manufacturer specifications.
• This test verifies the pump's ability to generate the required pressure.

Delivery Volume Testing:

• Measure the amount of fuel delivered by the pump over a specific time period.
• Compare the measured volume to manufacturer specifications.
• This test verifies the pump's ability to deliver the correct amount of fuel.

Timing Checks:

• Verify the injection timing using appropriate tools and procedures.
• This ensures that fuel is injected at the correct point in the engine's cycle.

Leakage Tests:

• Check for fuel leaks around the pump's body, seals, and connections.
• This prevents fuel loss and potential fire hazards.

Electronic Control Tests (if applicable):

• Use a scan tool or diagnostic equipment to check the operation of the pump's electronic controls.
• Verify that the pump is responding correctly to control signals.

2. Injector Tests (Gasoline and Diesel):

Spray Pattern Testing:

• Remove the injectors and observe the spray pattern.
• A good injector will have a fine, even mist.
• A poor spray pattern indicates a clogged or damaged injector.

Resistance Testing:

• Use a multimeter to measure the resistance of the injector coil.
• This checks for open or shorted circuits.
• Compare readings to manufacturer specifications.

Pulse Testing (Gasoline):

• Use a noid light or oscilloscope to check for electrical pulses to the injectors.
• This verifies the ECU's control of the injectors.

Leakage Testing:

• For diesel injectors, high pressure pop off testing is used to check for internal leakage, and proper opening pressure.
• For gasoline injectors, check for fuel dripping from the injector tip.

Volume Testing:

• Measuring the amount of fuel delivered by each injector over a set period of time. This can be done with specialized injector testing equipment.

3. Fuel Pump Tests (Gasoline and Diesel):

Pressure Testing:

• Connect a fuel pressure gauge to the fuel line near the engine.
• Measure the pump's delivery pressure at various engine speeds.
• Compare readings to manufacturer specifications.

Delivery Volume Testing:

• Measure the amount of fuel delivered by the pump over a specific time period.
• Compare the measured volume to manufacturer specifications.

Electrical Testing:

• Check the pump's voltage and amperage draw.
• This verifies the pump's electrical integrity.

Leakage Tests:

• Check for fuel leaks around the pump's body, seals, and connections.
• Check for leaks in the fuel lines.

Noise Testing:

• Listen for unusual noises from the fuel pump. Excessive noise can indicate a worn or failing pump.

Test Running Engine

1. Initial Start-Up:

• Start the engine and listen for any unusual noises.
• Observe the idle speed and smoothness.
• Check for any fuel or fluid leaks.
• Monitor the exhaust for unusual smoke or odors.

2. Warm-Up Phase:

• Allow the engine to reach operating temperature.
• Observe the engine's behavior during warm-up.
• Check for smooth acceleration and deceleration.
• Monitor the engine temperature gauge.

3. Road Test (If Applicable):

• Drive the vehicle under various conditions:
  • City driving (stop-and-go).
  • Highway driving (constant speed).
  • Acceleration and deceleration.
• Observe engine performance, fuel economy, and overall vehicle behavior.
• Listen for any unusual noises or vibrations.

4. Final Inspection:

• Check for any leaks or loose connections.
• Re-check fluid levels.
• Use a scan tool to check for any new DTCs.

Faults and Remedies

Poor Idle:

• Fault: Vacuum leaks, faulty idle air control (IAC) valve, incorrect idle mixture.
• Remedy: Check for vacuum leaks, replace IAC valve, adjust idle mixture.

Misfires:

• Fault: Faulty injectors, ignition problems, low fuel pressure.
• Remedy: Test and replace injectors, check ignition system, check fuel pressure.

Poor Acceleration:

• Fault: Clogged fuel filter, faulty MAF/MAP sensor, low fuel pressure.
• Remedy: Replace fuel filter, test and replace MAF/MAP sensor, check fuel pressure.

Engine Stalling:

• Fault: Faulty fuel pump, faulty crankshaft position sensor, vacuum leaks.
• Remedy: Test and replace fuel pump, test and replace crankshaft position sensor, check for vacuum leaks.

Increased Fuel Consumption:

• Fault: Faulty oxygen sensor, leaking injectors, incorrect air/fuel mixture.
• Remedy: Test and replace oxygen sensor, test and replace injectors, adjust air fuel mixture.

Excessive Smoke:

• Blue smoke: oil burning.
• Black smoke: rich fuel mixture.
• White smoke: coolant burning.
• Remedy: Diagnose and address the specific cause of smoke.

Check engine light illumination:

• Fault: various sensor or actuator failures.
• Remedy: scan for diagnostic trouble codes, and repair the related components.

Trip Computer

Function:

• A trip computer provides information about fuel economy, average speed, distance traveled, and other driving data.
• It can be used to monitor fuel consumption and detect changes in engine performance.
• It gives the driver feedback about the efficiency of the engine.

Role in Testing:

• During a road test, the trip computer can provide real-time feedback on fuel economy, helping to identify any issues with fuel delivery or engine efficiency.
• Changes in fuel economy can indicate problems with the fuel injection or carburetor system.

Limitations:

• Trip computer readings can be affected by driving conditions, such as traffic, terrain, and driving style.
• They should be used as a general guide and not as a substitute for accurate diagnostic testing.

Clearing Fault Codes

1. Repair the Underlying Issue:

• Crucial Step: Clearing fault codes without addressing the underlying problem is pointless. The codes will simply reappear.
• Diagnostic Process: Use a scan tool, multimeter, or other diagnostic equipment to identify the root cause of the fault code.
• Repair: Perform the necessary repairs, such as replacing a faulty sensor, repairing a wiring issue, or fixing a vacuum leak.

2. Use a Scan Tool:

• Connection: Connect a scan tool to the vehicle's OBD-II port.
• Access Codes: Turn on the ignition (engine off) and use the scan tool to access the stored fault codes.
• Clear Codes: Select the "Clear Codes" or "Erase Codes" function on the scan tool.
• Verification: After clearing the codes, use the scan tool to verify that they have been successfully erased.

3. Battery Disconnection (Less Common):

• Older Vehicles: In some older vehicles, disconnecting the battery (negative terminal first) for a period of time (typically 15-30 minutes) can clear fault codes.
• Modern Vehicles: This method is less reliable in modern vehicles and can sometimes cause other issues, such as resetting learned engine parameters or triggering security systems.
• Not Recommended: It is generally recommended to use a scan tool to clear fault codes.

4. Drive Cycle (If Required):

• Readiness Monitors: After clearing fault codes, the ECU may need to perform a drive cycle to complete readiness monitors.
• Drive Cycle: A specific sequence of driving conditions that allows the ECU to test various systems.
• Verification: Use a scan tool to check the status of readiness monitors.
• Inspection/Emissions: some inspections and emissions testing require that the readiness monitors be complete.

OBD Codes (On-Board Diagnostics Codes)

• Standardized Codes: OBD-II codes are standardized, meaning that the same code generally refers to the same fault across different vehicle manufacturers.
• Structure: OBD-II codes consist of a five-character alphanumeric code, such as P0300.
  • First Character:
    • P: Powertrain (engine, transmission)
    • B: Body (interior, exterior)
    • C: Chassis (brakes, suspension)
    • U: Network (communication)
  • Second Character:
    • 0: Standardized OBD-II code
    • 1, 2, 3: Manufacturer-specific code
  • Third Character:
    • Indicates the specific system:
      • 1: Fuel and air metering
      • 2: Fuel and air metering (injector circuit)
      • 3: Ignition system or misfire
      • 4: Auxiliary emissions controls
      • 5: Vehicle speed control and idle control system
      • 6: Computer output circuit
      • 7: Transmission.
      • 8: Transmission.
      • 9: Transmission.
      • 0: high voltage battery.
  • Fourth and Fifth Characters:
    • Indicate the specific fault within the system.
• Importance:
  • Diagnosis: OBD codes provide valuable information for diagnosing vehicle problems.
  • Troubleshooting: They help technicians pinpoint the source of a fault and guide them through the repair process.
  • Emissions Compliance: OBD-II systems are designed to monitor emissions-related systems and ensure compliance with regulations.