Aeon 350cc, Service Manual

Page: 109 / 192

ELECTRONIC FUEL INJECTION
5-109
The valve needle in the injector is opened electro magnetically,
and the pressure in the fuel rail forces fuel down through the
inside. The “director plate” at the tip of the injector (see inset)
contains a series of calibrated openings, which directs the fuel
into the intake port in a cone-shaped spray pattern.
The injector is opened and closed once for each crankshaft
revolution, however only one-half the total amount of fuel
needed for one firing is injected during each opening. The
amount of fuel injected is controlled by the ECU and
determined by the length of time the valve needle is held open,
also referred to as the “injection duration” or “pulse width”. It
may vary in length from 1.5-8 milliseconds depending on the
speed and load requirements of the engine.
FUEL INJECTOR SERVICE
Injector problems typically fall into three general categories
electrical, dirty / clogged, or leakage. An electrical problem
usually causes one or both of the injectors to stop functioning.
Several methods may be used to check if the injectors are
operating.
• With the engine running at idle, feel for operational vibration,
indicating that they are opening and closing.
• When temperatures prohibit touching, listen for a buzzing or
clicking sound with a screwdriver or mechanic's stethoscope.
• Disconnect the electrical connector from an injector and
listen for a change in idle performance (only running on one
cylinder) or a change in injector noise or vibration.
NOTE: Do not apply voltage directly to the fuel
injector(s). Excessive voltage will burn out the
injector(s). Do not ground the injector(s) with the
ignition on. Injector wills open/turn on if relay is
energized.
If an injector is not operating, it can indicate either a bad
injector, or a wiring/electrical connection problem. Check as
follows:
Injector leakage is very unlikely, but in rare instances it can be
internal (past the tip of the valve needle), or external (weeping\
around the injector body). The loss of system pressure from the
leakage can cause hot restart problems and longer cranking
times. Injector problems due to dirt or clogging are unlikely
due to the design of the injectors, the high fuel pressure, the
use of filters and the detergent additives in the gasoline.
Symptoms that could be caused by dirty/clogged injectors
include rough idle, hesitation/stumble during acceleration, or
triggering of fault codes related to fuel delivery. Injector
clogging is usually caused by a buildup of deposits on the
director plate, restricting the flow of fuel, resulting in a poor
spray pattern. Some contributing factors to injector clogging
include; dirty air filters, higher than normal operating
temperatures, short operating intervals and dirty, incorrect, or
poor quality fuel. Cleaning of clogged injectors is not
recommended; they should be replaced. Additives and higher
grades of fuel can be used, as a preventative measure if
clogging has been a problem.
FUEL INJECTOR TEST
The fuel injectors are non-serviceable. If fault code diagnosis
indicates a problem with injector, test the resistance of the fuel
injector(s) by measuring the harness pin terminals.
Fuel Injector Resistance Specification:
13.8 - 15.2
Ω
(25
℃ ℃ ℃ ℃
/ 77
℉ ℉ ℉ ℉
)
FUEL PUMP