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Fuel Injectors; Operation Overview; Fuel Injector Troubleshooting - Polaris RZR XP 1000 Service Manual

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Operation Overview

The fuel rail
, located on the intake manifold, retains
the fuel injectors
to the intake assembly. O-rings on
both ends of the injectors prevent external fuel leaks and
also insulate the injectors from heat and vibration.
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 each
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.
The ECU gathers fuel injection timing information from
the Crankshaft Position Sensor (CPS) and the Pedal
Position Sensor (PPS) to allow for sequential fuel
9925724 R01 - 2014-2015 RZR XP 1000 / RZR XP4 1000 Service Manual
© Copyright 2014 Polaris Industries Inc.

Fuel Injector Troubleshooting

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
• 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. lnjector (s) will 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.


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