The Common Faults in Petrol Injectors

Written by jack hathcoat
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The Common Faults in Petrol Injectors
Modern vehicles are incapable of significant fuel mileage without fuel injection systems. (Transport, Blue Car image by Astroid from Fotolia.com)

Petrol, or fuel, injectors manage fuel delivery in modern automobiles. With the help of computers and electronics, these injectors have the ability to supply the exact amount of fuel needed under a wide variety of driving conditions. Five specific regions make up a fuel injector, each with a potential for failure. Examining, cleaning and testing is called for when fuel injector problems arise.

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Injector O-Rings

The most common failure item on fuel injectors are the O-ring seals. These seals are under pressure and, when combined with engine heat, may leak. A sure indicator of a problem is a faint smell of gas. If there is a leak, remove the injector fuel rail and replace all of the O-rings. They are made of a special material and standard, black O-rings will swell before failure. Purchase O-rings made specifically for gasoline environments.

Injector Body

The body of the injector is made of high-impact, heat-resistant plastic. This plastic rarely fails, but hairline stress cracks can appear. In these cases, there is no alternative but to replace the injector. To determine if the injector body is defective, carefully inspect the plastic, and if needed, use magnification. Often it will appear that the O-ring is at fault. After repeated O-ring replacement, however, a leak that is still present usually means the problem is with the injector body. Another option is to swap injector locations. If the leak follows to the new location, the injector body is defective.

Electrical Connectors

Electrical connections rarely fail; it is much more likely that the connector is faulty. To test this, remove the electrical connector and apply battery voltage directly to the two prongs attached to the injector body. If the injector is working, you will hear a faint "click" as the internal injection valve retracts. If it fails this test, replace the injector. A good source for defective electrical connectors is salvage yards. Recycle the used connector by soldering it in place and using heat-shrink tubing to protect the soldered connection.

Inlet and Outlet Ports

A little-know problem that creates severe misfires is when the inlet port of the injector becomes contaminated with debris. This blocks the fuel flow to the engine. The injector is fine but unable to flow gasoline through to the engine cylinders. Inside the port is a finely woven screen. During inspection, if you see debris and dirt in the port, the main fuel filter has failed. Soak the injector in a carburettor-cleaning solvent to remove the debris and replace the fuel filter. Also inspect the outlet port. If it is dirty and covered with carbon build-up, place it -- along with all of the injectors -- in solvent to soak overnight. Replace all of the O-rings before reinstallation.

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