Maintenance & Troubleshooting for Portable and Standby Diesel Generators

Diesel Fuel Injector Service Video

Diesel engines use direct fuel injection -- the diesel fuel is injected directly into the cylinder.

The injector on a diesel engine is its most complex component and has been the subject of a great deal of experimentation -- in any particular engine, it may be located in a variety of places. The injector has to be able to withstand the temperature and pressure inside the cylinder and still deliver the fuel in a fine mist. Getting the mist circulated in the cylinder so that it is evenly distributed is also a problem, so some diesel engines employ special induction valves, pre-combustion chambers or other devices to swirl the air in the combustion chamber or otherwise improve the ignition and combustion process.

The position of the fuel injector inside the combustion chamber is also very important. Small adjustments are made by either adding or subtracting some copper washers to increase or decrease how much it will protrude into the engine. Avoid unnecessary removal as the copper can compress affecting the distances and also result in compression loss if it does not seal correctly.

Some diesel engines contain a glow plug. When a diesel engine is cold, the compression process may not raise the air to a high enough temperature to ignite the fuel. The glow plug is an electrically heated wire (think of the hot wires you see in a toaster) that heats the combustion chambers and raises the air temperature when the engine is cold so that the engine can start.

Removing the injector is fairly simple. There is a fuel supply line (steel line) to each injector. There is also a return line (smaller one). Both of these lines will have to be removed. On the return line be careful not to lose the little compression washers. Remove the two bolts that hold the injector in place. The injector should pull out. Be careful not to lose the copper washer that usually comes out with it.

Inspect the end of it. There should be tiny holes in the end where the fuel sprays out.

Unless you have a injector tester you will have to take them to a Diesel mechanic and have them tested. They will hook them up to a machine that can apply the PSI required to see if they are working properly. It shouldn't cost that much.