1. ELECTRONIC FUEL INJECTION

2. Introduction
• Strict emission standards require precise
fuel delivery
• Computers used to calculate fuel needs
• EFI very precise, reliable & cost effective
• EFI provide correct A/F ratio for all loads,
speeds, & temp ranges

3. The Fuel Injector
• Electromechanical device
• Controlled by PCM
• Engine rpm determines when injector
opens
• How long it stays open determined by:
– Engine temp
– Engine load
– Throttle pos.
– O2 sensor voltage

4. Throttle Body Injection (TBI)
• First injection
unit used
• Housing similar
to Carb
• One or two
injector
• One or two of
these units
mounted to
intake manifold
FIG 6-40 CLASS

5. LOW PRESSURE FUEL
INJECTOR
• 13-16 psi
operating
pressure
• Ball style
pintle
• Easily
replaceable

6. GM’s Crossfire Injection

7. Multi-Port Fuel Injection
• One injector per cylinder
• Mounts in intake
manifold, sprays directly
at intake valve
• Fired in groups or
individually (SFI)
• Ram Tuning for denser
air charge
• Lower A/F temps
• Leaner mixture during
warm-up

8. Bosch & Delphi Multec

9. Fuel Pressure Regulator
• Located at end of fuel rail
• Maintains constant pressure at injectors
• Internal chamber contains a diaphragm
– Pressurized fuel on one side
– Manifold vacuum & spring tension on other
• Manifold vacuum pulls up on diaphragm,
metering fuel that is returned to tank
• Excess fuel pressure can overcome spring
tension, allowing fuel to return to tank
• Increases in manifold pressure causes spring
tension to push diaphragm down, blocking return
line, increasing pressure in rail.

10. Fuel Pressure Regulator

11. Fuel
return
Vacuum hose
connection Fuel rail
Fuel Pressure Regulator

12. Central Port Injection (CPI)
• Injector located
in center of
intake manifold
• 60 psi system
• 6 or 8 poppet
valves attached
to one TBI type
injector

13. Central Multi-Port Injection
(CMPI)
• Similar to
CPI
• Individual
injectors,
with poppet
valves

14. CMPI Connections
Electrical Connectors Fuel Supply Fuel Return

15. CMPI Up Close
Fuel Pressure Regulator
Cylinder
Numbers

16. Poppet Nozzles
• Contains a check
ball & extension
spring
• Regulate the flow of
fuel into cylinder
• Fuel flows when
pressure exceeds
40 psi
• Ball reseats when
pressure drops

17. Injector Testing
• Coil Test – Specific current supplied, measures
voltage drop
• Injector Balance – Inj. Energized for a precise
time frame, record fuel pressure drop

18. Injector Circuit Testing
• Noid lights
• Simple test light that plugs into injector
connector
• Light flashes with each electrical pulse

19. Injector Cleaning
• Periodic cleaning
removes varnish &
other deposits
• Pressurized canister
dispenses cleaning
solution
• MUST disconnect
fuel pump!