Polaris Sportsman 850 Touring EPS, Service Manual, Page: 182 / 510

4.28
FUEL INJECTORS
OPERATION OVERVIEW
The fuel injectors mount into the throttle body, and the
fuel rail attaches to the top end of them. O-rings on both
ends of the injector prevent external fuel leaks and also
insulate it from heat and vibration.
REF.
DESCRIPTION
q
Fuel Injectors
w Damper
e Pressure Valve
When the key switch is on, the fuel rail is pressurized,
and the EFI relay provides voltage to the injectors.
During engine operation, the ECU completes the ground
circuit, energizing the injectors. The valve needle in the
injector is opened electromagnetically, and the pressure
in the fuel rail forces fuel down through the inside. The
“director plate” at the tip of the injector contains a series
of calibrated openings which directs the fuel into the
intake port in a cone-shaped spray pattern.
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 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.
NOTE
Do not apply voltage directly to the fuel injectors.
Excessive voltage will burn out the injectors. Do not
ground the injectors with the ignition on. The injectors
will open if the EFI 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 O-RINGS
1. Any time an injector is removed, you must replace the
upper and lower O-rings.
2. Always lubricate NEW injector o-rings with clean,
silicone-free motor oil.
NOTE
Apply oil sparingly and avoid contaminating the pintle
valve / jet surface and upper inlet port.
3. Install NEW o-rings onto top and bottom of injector
FUEL SYSTEM