Thursday, August 8th, 2013

Fuel Injectors: The most blamed part of the fuel supply system

Fuel Injector

Fuel Injector

Fuel Injector Basics

Fuel injectors are probably the most blamed part of the fuel supply system, mostly because of ignorance of the part and how it works, and how the automotive controls make them work.

First let’s get down to basics, a fuel injector is nothing more than a nozzle that aims a cone shaped burst of fuel on either the piston head or the intake valve. This cone shaped cone of fuel is atomized or mixed with air to provide a measured and aimed fuel charge into the combustion chamber to facilitate a clean and controlled burn for upmost efficiency.

The ideal proportion of air to fuel is 14.7 parts of air to one part of fuel. This is what is known as the stoichiometric air fuel ratio. In the years before, when vehicles were carburetored, it was more akin to dumping a bunch of fuel down a shaft, letting it mix with whatever air was available and having it sucked down running tubes or runners under vacuum and sucked into the combustion chamber to be burned.

Single Point Injectors

Initially many fuel injected vehicles were which were called single point injectors or throttle body injection systems. These systems were basically a glorified carburetor with the exception that the fuel delivered was must more atomized because of the pressure the fuel is delivered under. Then came ported fuel injection in which there is an injector for every cylinder. This is the system that we are going to attack today.

Beauty of the Fuel Injector

Before we get too technical lets breakdown the beauty of the fuel injector. Think of a fuel injector as an adjustable shower head. As you twist the control head you can change the shape and pressure of the water that comes out of the head. That is the beauty of fuel injection.

What Does a Fuel Injector Do?

In real life a fuel injector is a nozzle that sprays atomized fuel in a conical shape on to the intake valve to complete the combustion process. This “nozzle” has a fixed orifice on the business end of the injector, inside of the injector is a pintle or a small ball the completely seals the orifice when it is set in its seat. Enter a small resistor that when activated with a pulsating 12 volt charge creates a magnetic field and lifts the ball or pintle so that fuel can flow unrestricted into the combustion chamber. And that’s all there is to the action and operation of a fuel injector.

Ethanol Damage

Ethanol Damage

The Enemy is Dirt and Contamination

Given this simplistic view of the operation of a fuel injector, it’s obvious that its greatest enemy is dirt or contamination. Injection systems that are never maintained have little bits of dirt and grit that is being forced through a measured orifice suspended in fuel under pressure. Like the Colorado River eroded the river bed into the Grand

Misfires and Poor Fuel Economy

Canyon so too is that orifice eroded and misshaped. When this happens the ball or pintle cannot seal the orifice and the fuel spray becomes misshaped and loses pressure or leaks fuel into the combustion chamber causing poor fuel economy, or hard starting, or fouled plugs. Transversely if these minute pieces of contamination are left to plug the orifices or the injector filters thus causing misfires or lean burning engines.

Fuel Injector Spray Pattern

Fuel Injector Spray Pattern

What would be the easiest way to maintain these injectors, and to keep the fuel delivery system working in a most efficient way? The simplest way is to replace the fuel filter annually, by keeping the air filter cleaned, and using only Tier 1 fuels and by cleaning the fuel rails, and injectors with a special and caustic injector cleaners.

Finally by never letting the fuel level go below ½ tank you not only do not pick up debris from the bottle of your fuel tank, but keep the fuel pump cool and lubricated thus allowing the pump to last even longer even saving you the consumer more money through maintenance.

Read: Five Tips for Maintaining your Fuel Pump

When it comes down to picking fuels try to always use Branded fuel companies. They are companies like Mobil, Shell , Chevron, and BP to name a few. Companies that have no affiliation to oil companies are basically fuel wholesalers and have no say in the amount of additives and cleaners in their fuel and even less say on the amount of Ethanol that is added at every fuel rack.

Try to run high test every 4th or 5th tankful so that the chemical detergents can clean these injectors and as you drive. Next week we’ll talk about all the controls that keep these injectors running to clean and efficient, saving you MONEY.


Gregg’s Automotive Maintenance & Repair Center

236 S. Tamiami Tr.
Punta Gorda, Fl. 33950
Auto Repair, A/C Repair, Oil Change, Brake Repair & Transmission Services