Basic EFI

1. Basic EFI

2. Layout Diaphragm Spring Manifold Vacuum Injectors Seat Pintle Fuel Pump Return Line Fuel Tank

3. ECM Controls • To determine the amount of fuel required, the ECM needs to know how much air is entering the engine • Two methods for measuring airflow • Speed-Density • Mass Airflow

4. Speed-Density • The ECM receives input from • MAP (engine vacuum) • TPS (throttle position) • CTS (coolant temperature) • IAT (air temperature) • O2 (rich/lean indicator) • CKP (engine RPM)

5. Speed-Density • Based on the engine vacuum, engine rpm, intake air temperature, and the pre-programmed volumetric efficiency of the engine, the computer calculates the amount of air entering the engine • Engine operating temperature, throttle position, and rich/lean indications from the O2 are then used to calculate/adjust the required amount of fuel

6. Speed Density O2 CTS TPS MAP Airflow ECM ECM CKP IAT Injectors

7. Mass Airflow • Based on the airflow data received from the MAF engine operating temperature, throttle position, and rich/lean indications from the O2 are used to calculate/adjust the required amount of fuel

8. Mass Airflow O2 CTS TPS CKP Airflow ECM ECM MAF Injectors

9. Fuel Injectors • Solenoid type • ECM controls the ground side of the injector circuit • Poppet type • When pressure reaches a predetermined level the injector is forced open • Diesel, CFI, CIS

10. Types of Fuel Injection • Throttle Body Injection (TBI) • Port Fuel Injection (PFI) (MPFI) • Central Point Injection (CPI) • Gasoline Direct Injection (GDI) • Constant Injection System (CIS) • Different manufacturers may call similar systems by different names

11. Throttle Body Injection (TBI) • The throttle body looks similar to a carburetor • The throttle body contains the fuel injectors and usually the pressure regulator • Pressure regulator does not use vacuum to cut back fuel pressure during high vacuum conditions

12. Port Fuel Injection • Throttle body only controls the amount of air entering the engine • Injectors are located in each intake port • One injector per cylinder • May use an additional cold start injector • Intake manifold only has to deliver air therefore problems with fuel puddling are greatly reduced • Injectors may be batch fired or sequentially fired (SFI) • Tuned port injection operates the same as port fuel injection, except the intake manifold is designed for optimal cylinder filling

13. Port Fuel Injection

14. Port Fuel Injection

15. Port Fuel Injection (Batch Fired)

16. Cold Start Injector

17. Central Point Fuel Injection • Used on GM Vortec engines • Central injection assembly located in the lower intake • Fuel flow controlled by electric solenoids in the CPI assembly • May be batch fired or sequentially fired • Pressure regulator located in the CPI assembly • Actual fuel injectors are mechanical • Won’t open unless the specified fuel pressure is present • Operates at a relatively high fuel pressure (55-61 PSI)

18. Central Point Fuel Injection

19. Central Point Fuel Injection Poppet Injector

20. Central Point Fuel Injection CPI Assembly Pressure Line ECM Actuated Solenoid-type Injectors Return Line Pressure Regulator Poppet Injectors

21. Constant Injection System (CIS) • Mechanical injection system • Used extensively by the Germans • Amount of fuel delivered is controlled by altering fuel pressure at the injector rather that injector on time • Uses a air vane to sense engine airflow and change fuel delivery rates

22. Constant Injection System Mechanical Injector Metering Valve Differential Pressure Valve Filter Pump Pressure Regulator Air Vane Tank

23. Constant Injection System (CIS-E)

24. Idle Speed Control • In EFI systems the ECM controls idle speed • Throttle opening control • Throttle Air Bypass • To increase idle speed, more air is bypassed by the throttle blades • To decrease idle speed, less air is bypassed by the throttle blades

25. IDLE SPEED CONTROL • To comply with federal emissions standards, idle speed control systems are used • Idle speed controlled by electronic module • Earlier systems, engines idled in open loop • Idle systems depend on inputs to PCM

26. Throttle Kicker controlled by Vacuum Diaphragm • Electrically controlled by solenoid • Operates during engine warm up, with air conditioning on and engine overheating • Some act as a dashpot 327C

27. Throttle Kicker and Idle Stop Solenoid • Electrically controlled • Vacuum operated throttle kicker for additional load • Allows curb idle speed to be lower • Controlled by PCM • Must be adjusted 327C

28. IDLE SPEED CONTROL MOTOR (ISC) • PCM controlled • Reversible gear drive dc motor • PCM reverses polarity • Has idle tracking switch • Must be adjusted 325C

29. ISC Schematic

30. IDLE AIR CONTROL (IAC) • Used with Fuel Injection systems • PCM controlled Stepper motor • Diverts air around throttle plate • Do not over extend when replacing • Not adjustable

31. Throttle Body IAC Location • Screws into throttle body • Must be careful to not over-tighten • Must keep passages clean • Can use Scanner to diagnose idle problems

32. 508L IAC SCHEMATIC • Contains two motor windings • Can test with ohmmeter (GM are 40 - 80 ohms) • Use IAC Test tool to check operation • Can monitor operation with Scanner

33. IAC SCOPE PATTERNS • Typical patterns • Compare patterns to known good patterns • Some IAC’s operate on 12 volts and others on less voltage • IAC operates with a duty cycle

34. ADJUSTING CURB IDLE(Idle Hardstop or Minimum Idle speed) • Minimum idle rpm is factory adjusted • Idle must be adjusted correctly • Passages must be clean • Some systems, you must adjust TPS also 502L

35. IDLE SPEED ADJUSTMENT • Must shut off idle air to adjust minimum idle speed • Use idle plug on TBI units • Other systems, you just turn a screw to control air flow (idle rpm)

36. Ford Pulse Width Idle Control Motor (Bypass Air Valve) • Depending on the % on time form the ECM the pulse width motor allows more or less air to bypass the throttle blades ICM Throttle Body Intake