Inject Horsepower & Fuel Economy Back Into Your Ride

Automotive fuel injectors fall into two categories: electronically actuated solenoids or hydraulically operated. Some gasoline applications use hydraulic injectors however typically you will only find them in diesel engines. For our purposes here, we’ll focus on electronically actuated fuel injectors.

ELECTRONIC FUEL INJECTORS

Electronically actuated fuel injectors are solenoids that spray a precise amount of fuel into the combustion chamber to mix with the air. Modern engines use a high-pressure multiport fuel injection system where injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port. Prior to multiport fuel injection design, low-pressure throttle body fuel injection systems (a.k.a. single point injection) were used that evolved from carbureted fuel systems.

A fuel injector contains a pintle that closes off an orifice at the nozzle end (Figure 1). When electric current is supplied to the injector, the armature and needle move a short distance against a spring, allowing fuel to flow out the orifice. Because the fuel is under high pressure, a fine spray is developed in the shape of a hollow cone. The spraying action atomizes the fuel, adding to the air entering the combustion chamber.

The injectors are energized individually in a sequential order by the Powertrain Control Module (PCM). A few other devices the PCM regulates include: ignition timing, air/fuel ratio, emission control devices, cooling fan, charging system and idle speed.

Over time, and depending on fuel and air quality (dirt), fuel injectors begin to drip rather than spray. To run efficiently, fuel injected engines require a constant flow of pressurized fuel. When fuel injectors become clogged, this impacts the vehicles performance, driveability and fuel economy. Problems such as hesitation, power loss, stalling and dieseling can be caused by fuel injection problems. However a number of other circumstances can cause the aforementioned symptoms. Read about engine misfire diagnosis in Diagnostics on page 48.

SERVICE

Sometimes fuel injectors need to be replaced. They either fail or they’re too badly clogged to be “driven clean” with cleaning solutions added to the fuel. Mopar offers fuel injectors that are O.E quality and designed specifically for Chrysler, Jeep® or Dodge vehicles.