© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 31 Fuel Injection System Diagnosis and Service

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. FI Diagnosis FI systems are integrated into engine control systems Self-test modes may be available Performance complaint may be caused by something unrelated to the fuel system

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Battery condition Proper starting and charging system operation Condition of all fuses Wiring harness routing and condition Vacuum hose routing and condition MIL is working correctly Preliminary Checks

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Air induction and exhaust systems for leaks Emission control device operation and condition Cooling system condition Ignition system operation Engine mechanical condition Gasoline quality Preliminary Checks

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Relieve fuel pressure before disconnecting components Never turn the ignition on with fuel system components disconnected Use the proper test equipment Turn off the ignition switch before connecting test equipment Service Precautions

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Disconnect both battery cables before arc welding an computer-controlled vehicle Never disconnect the battery while the engine is running Avoid static electricity charges when handling electronic components Isolate or disable high-voltage systems before testing or servicing the fuel system Service Precautions (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Basic EFI System Checks FI problems usually result in no-start or poor driveability problems Check MIL first No MIL or no DTC does not mean the system is operating normally Fuel trim should be observed regardless of if a DTC is set

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Trim

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Trim Following O2 Output

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Short-Term Fuel Trim (STFT) – The computer makes small corrections based on oxygen sensor information – Is shown on a scan tool in percent of increase or decrease Adaptive Fuel Control

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Long-Term Fuel Trim (LTFT) – The computer makes corrections if a condition continues to exist – Is shown on a scan tool in percent of increase or decrease Adaptive Fuel Control

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Trim The fuel trim monitor looks at the sum of the STFT and LTFT If the PCM detects an extreme change in fuel strategy, a DTC will set A fuel system DTC does not mean the fuel system is at fault

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Trim (Cont.) STFT adjustments are temporary and are not stored in PCM memory LTFT adjustments are stored and influence base timing and injector pulse width

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Trim (Cont.) STFT responds to O 2 S information Once a certain engine temperature is reached, the PCM starts updating LTFT This is based on engine speed and STFT If STFT shifts 3% and stays there, the PCM adjusts LTFT to bring STFT close to 0% correction

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Since V-type motors have two sets of O 2 S, a pair of STFT and LTFT numbers will show on scan tool Both can vary in correction from bank to bank Other systems can cause fuel trim to be out of range: – Air induction, PCV, ECT, ignition, exhaust, and O 2 or A/F sensors Fuel Trim (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Oxygen Sensor Diagnosis Signal should vary between 0 and 1 volt Activity is best checked with a scope Voltage should switch quickly - A and C

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Knowledge Check How does oxygen sensor data affect fuel trim?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. A/F Sensors Voltage toggling does not occur Scan tools not designed to read A/F sensors will display voltage similar to an HO 2 S – Sensor voltage stays around 0.66 volts – If lean, voltage increases to about 0.8 volts Scan tools designed for A/F sensors will show a range of 2.4 to 4.0 volts – Voltage increases when lean and drops when rich

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Air Induction System Checks All air entering the engine must be accounted for, especially on MAF equipped engines Perform a careful inspection of all hoses Vacuum leaks will not affect speed-density systems as much as MAF system

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Vacuum Leak

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Check for Leaks

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Airflow Sensors MAF sensors measure intake air before the throttle plate Air bypassing the MAF will cause a lean condition A hot wire MAF can become dirty or contaminated, also causing a lean condition

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Increased manifold pressure (lower vacuum) causes increased injector pulse width Reason for increased manifold pressure - open throttle, vacuum leak, restricted exhaust, does not matter Vacuum leaks with MAP sensors decreases idle air control counts Manifold Absolute Pressure (MAP) Sensors

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. MAP Data

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Throttle Body Designed to allow a certain amount of air to pass at a particular amount of throttle opening Deposits reduce air flow Some throttle bodies have a special coating and should not be cleaned with chemicals

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Knowledge Check Technician A says a vacuum leak can make the engine run lean. Technician B says a vacuum leak has no effect on a MAF equipped engine. Who is correct?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel System Checks Check fuel delivery – Low pressure can cause a lean condition or no-start – High pressure can cause a rich condition

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel System Checks (Cont.) Check fuel pressure and how long pressure holds with the key off Inspect regulator for leaks

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. At Rest Test – Determines causes of system not holding pressure Power Test – Uses a voltmeter or Noid light to determine if the injector is receiving power and is being pulsed to ground Injector Tests

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuel Injector Control Test

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Injector Tests (Cont.) Resistance Test – Uses an ohmmeter to check condition of injector coils

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Balance Test – Helps isolate a clogged or dirty injector Sound Test – Uses a stethoscope to listen for clicking of injector Flow Test – Checks injectors after removing them from the engine Oscilloscope Tests Injector Tests (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Injector Balance Test

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Conventional Injector Waveform

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Peak and Hold Injector Waveform

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Pulse Modulated Injector

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Injector Tests (Cont.) For all injector types, there should be a clean, sudden drop in voltage when turned on Check voltage spike levels High coil resistance or a shorted coil will reduce inductive kick when turned off Current ramping can be used to compare current flow and voltage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Injector Cleaning Never soak an injector in cleaning solvent Never use a wire brush, pipe cleaner, toothpick, or other tool to clean opening Injector cleaning runs a chemical through the injector to remove deposits

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

When removing and reinstalling components, lightly lubricate O-rings with engine oil or transmission fluid Cap injector openings in the intake to prevent the entry of dirt or debris Cap all fuel rail and injector openings Do not use compressed air to flush or clean the fuel rail or injectors Fuel Rail, Injector, and Regulator Service

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Special GDI Checks Use an ohmmeter to check for opens or shorts in windings Typical fuel volume tests cannot be done due to high fuel pressures Scan tool will display fuel pressure

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Technician A says a restricted fuel injector can cause a lean condition. Technician B says an injector balance test may locate a restricted injector. Who is correct?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electronic Throttle Controls No idle speed adjustment necessary Idle speed can be monitored with a scan tool PCM must know base throttle position Follow learn/relearn procedures exactly Does not need to relearn after battery disconnect

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. ETC Data

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Idle Speed Checks – Non ETC Check linkage and vacuum lines Many different inputs will affect IAC: – Lower than normal TP signal – Higher than normal TP signal – Incorrect ECT signal – Stuck closed A/C switch

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Check IAC counts with a scan tool: – If counts are low or zero, look for a vacuum leak – If counts are higher than normal, look for a dirty or restricted throttle body – Look for count change while performing a wiggle test – Counts should be steady IAC System Tests

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Carbon Buildup

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Checking the Extension of an IAC

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Servicing the IAC Motor Some vehicles allow for IAC control via a scan tool If the IAC does not respond, further testing is required Carbon deposits in IAC passage can cause erratic idle speeds and stalling