This document provides an overview of fuel systems and their components and evolution over time. It discusses the basic parts of all fuel systems including the fuel tank, lines, pump and canister. It then covers the different types of fuel management systems from carbureted to various fuel injection systems. The document concludes with a timeline of fuel system developments and descriptions of key sensors and components involved in engine fuel control systems.

1. Fuel Systems

2. All Fuel Systems Have:
 Fuel Tank
 Fuel Pump
 Fuel Lines
 EVAP lines

3. Charcoal Canister

4. Fuel Pump

5. Fuel Filter

6. Fuel Management Systems
 Non Computer Controlled
 30’s to mid 80’s
 Computer controlled Carburetors
 Mid 80’s – 90’s
 Called OBD I
 Computer Controlled Fuel Injection
 Early 80’s – Current
 After 1996 called OBDII

7. Basic Powertrain Control
Module Operation
PCMInputs Outputs
Reduces 12v
battery voltage to
5v reference
voltage.
Sends digital or analog
voltage signal to PCM
depending on sensor
type.
Sends signal to control
actuator (typically ground).
PCM reads voltage drop from
actuator to verify working.

8. The BIG 5
1. TPS
2. MAP / MAF / VAF
3. ECT / IAT
4. CKP
5. O2 sensor

9. TPS=Throttle Position Sensor
Tells PCM throttle angle

10. How PCM measures airflow
• MAP=Manifold Absolute Pressure sensor
• Measures intake manifold pressure
• MAF=Mass Air Flow sensor
• Senses intake manifold flow electronically
• VAF=Volume Air Flow sensor
• Senses intake manifold flow mechanically

11. ECT=Engine Coolant Temp sensor
Tells PCM Coolant Temperature

12. IAT=Intake Air Temp sensor
Tells PCM intake air temperature

13. CKP=Crank Shaft Position sensor

14. O2 Sensor
Tells PCM Oxygen content in exhaust

15. Types of Fuel Systems
 Carbureted
 Fuel injection
 Throttle Body injection
 Port fuel injection
 Sequential port fuel injection

16. Fuel Systems Timeline

17. Choke Plate
Venturi
Throttle Plate
Idle circuit
Main jet
Float
Air
Air fuel mixture
Off Idle port

18. Various Carburetor types

21. Bosch Electronic Fuel Injection
The First!
 D-Jetronic-Druck or Pressure sensing,
used first on 1967 VW 1600
 K-Jetronic-Kontinuierlich or Continuous
flow, used first on 1974 Porsche 911
 L-Jetronic-Luft or Air pressure sensing,
used first in 1974. Many of todays injection
systems use many of the concepts of the
L-Jetronic system

22. Throttle Body Injection

23. Port Fuel Injection
 Single fuel injector mounted in intake port
near intake valve
 All injectors fire at same time
 Some fuel may puddle behind intake valve
 Electronic system for next level of fuel
control was too expensive then

24. Sequential Port Fuel Injection
 Also has single fuel injector mounted in
intake port near intake valve
 PCM now has ability to control injectors
one at a time to provide accurately timed
pulse just before intake valve opens
 This eliminates puddling of fuel
 Emissions go down, HP goes UP

25. Latest Developments
 Very high pressure pumps (2000psi) and
injectors make direct cylinder injection
possible
 Now have ability to inject fuel into cylinder
at any time, even during compression
stroke for better atomization
 By altering timing, lean burn during warm-
up allows much faster catalyst light-off
 HP takes another leap-over 400HP from
300ci now common from luxury car!!!

26. Fuel Rail

27. Fuel Injector

28. Diagnostic Data Link
 Pre 1996-Can be located anywhere
 Post 1996-Under dash by steering wheel

29. Scan Tool Data
 Codes (DTC’s)
 Freeze Frame Data (OBDII)
 Parameter ID information (Sensor Values)
 Bi-Directional Control
 Some OBD I
 All (but limited) OBD II

30. Scan Tools

31. Scan Tools
 Can cost between
 Under $50 for tool that just reads DTC’s
 $100-400 Reads codes and data
 $500-3,000 Reads Codes, data and
reprograms PCM’s
 & $3,000 and up Manufacturer specific scan
tools