About Fuel Injectors & Injector Cleaning

How does fuel injection work?

Fuel injection replaced carburetion as the principal form of fuel/air delivery to vehicles in the mid 1980s. The simple, efficient design offered a new standard of reliability and efficiency by delivering fuel in varying volume and frequency - a process that would become more sophisticated as electronics replaced mechanical components within the injection systems.

With a petrol engine, fuel is transferred via an electronic pump known as a fuel pump. This fuel subsequently passes though a filter that removes most contaminates that have entered (or corroded from) the fuel tank.

This filtered fuel then enters one end of a common feeding tube for an engine's fuel injectors called a fuel rail. The other end of this rail is met by a pipe that leads back to the fuel tank - called a return pipe. This pipe contains a fuel pressure regulator (essentially a resistor, or blockage) that ensures all fuel within the fuel rail is kept at a constant pressure (essential for precise metering of fuel).

The engine's injectors 'feed' from this pressurised fuel delivery circuit.


  Injector Cleaning  

The function of a fuel injector

Modern injection systems take into account air temperature, driver demand, air density, exhaust gas composition, crankshaft and camshaft positioning during fuelling. These variables are received by the engine's control unit (ECU) and directly affect both how much and how often fuel is injected into the engine's cylinder head.

  Injector Cleaning  

Types of injector

These 12 types of injectors account for most applications.

Bosch MFI (Mechanical Fuel Injection) (Ford Escort RS Turbo) Bosch top feed EFI (Electronic Fuel Injection) (BMW 850 CSi) Bosch top feed picoelectronic (Vauxhall Omega MV6)
Bosch MFI
(Mechanical Fuel Injection)
(Ford Escort RS Turbo)
Bosch top feed EFI
(Electronic Fuel Injection)
(BMW 850 CSi)
Bosch top feed
picoelectronic
(Vauxhall Omega MV6)
Weber top feed (Ford Sierra Cosworth 4x4) Weber picoelectronic top feed (Renault Clio 182 Trophy) Denso side feed (Toyota MR2 Turbo)
Weber top feed
(Ford Sierra Cosworth 4x4)
Weber picoelectronic top feed
(Renault Clio 182 Trophy)
Denso side feed
(Toyota MR2 Turbo)
Lucas top feed (disc type) (Rover 220 Coupe 'Tomcat' Turbo) Siemens picoelectronic top feed (Ford Fiesta Zetec-S) Rochester / GM (Multec ball type) (Vauxhall Nova GTE)
Lucas top feed (disc type)
(Rover 220 Coupe 'Tomcat' Turbo)
Siemens picoelectronic top feed
(Ford Fiesta Zetec-S)
Rochester / GM
(Multec ball type)
(Vauxhall Nova GTE)
JECS (Japan Electronic Control System, Co.) (Nissan 200SX S13 Turbo) Keihin (Honda Accord VTEC) Idle control valve (Bosch) (Peugeot 405 Mi16)
JECS
(Japan Electronic Control System, Co.)
(Nissan 200SX S13 Turbo)
Keihin
(Honda Accord VTEC)
Idle control valve (Bosch)
(Peugeot 405 Mi16)


About Injector Cleaning

How injector cleaning works

In addition to removing internal contaminates and lubricating internal parts prior to use, the following two common areas for injector deterioration are addressed.

Injector Spray Patterns

Spray patterns change due to varnishes and contaminates from the engine side of the injector adhering to the injector pintle and effectively obstructing the path of the injected fuel (it is also caused by using fuel supplied by some 'budget' retailers of petrol who decline to add sufficient amounts of polyetheramine to the base petrol. Polyetheramine is a highly effective fluidiser that inhibits adherence of contaminates to the injectors, valves, pistons and the cylinder head).

A correct spray pattern will produce a fine mist-like gas that burns both quickly and efficiently within the engine - processes known as atomisation and combustion respectfully. When a spray pattern deteriorates, these fine droplets of fuel no longer form an effective suspension with the air being drawn (or forced) into the engine. Symptoms of such deterioration include:

Some of these are also symptoms of clogged micro filters.

  Different Spray Patterns  
  1. Good spray pattern but weak supply (clogged filter)
  2. Poor spray pattern (obstruction in spray path)
  3. Poor spray pattern (obstruction in spray path)
  4. Very poor spray pattern (major obstruction in spray path)
  5. Good spray pattern with good supply (cleaned injector)
  6. Very poor spray pattern (major obstruction in spray path)

Injector fuel delivery

Each injector contains its own small filter to 'strain' foreign objects from the fuel supply entering the injector. These objects typically enter the fuel supply during refuelling and are too small to be caught by the main fuel filter. After around 50,000 miles of general road driving these contaminates caught in the injector's micro filters will reduce the maximum volume of fuel available to be delivered over a given period of time by about 5%.

In extreme cases fuel starvation can occur, causing any given engine cylinder to run 'lean', overheat and damage the engine internals (pistons and bores). Clogged or dirty injectors can be catastrophic for engines utilising forced induction (turbo or supercharged) as a situation where demand for fuel can exceed supply - causing cylinders to run lean and destroy the engine though the creation of excess heat. Clogged injectors will also introduce an unknown quantity when calculating safe over-boost levels for forced induction applications.

Fuel delivery is expressed in either the metric (xxxcc/min at x bar) or the imperial (xxxlbs/min at x bar). Demanding more than 80% of the maximum potential fuel supply of an injector at any point in the injection cycle is an unsafe process.