To prevent fuel injectors of a direct-injection engine from getting stuck or seized, always replace the O-ring and the gasket of the fuel injector in case of any of the following:
1. If the fuel injector has been pulled out.
2. If the fuel injector has been turned or moved just a little bit.
3. Whenever there is a sign of combustion gas leakage around the body of the injector.
See Fig. 1.
I would also recommend that you apply injector grease around the injector body before fitting the injector into the cylinder head.
Now I will explain why you should always replace the O-ring and gasket if your engine is under any of the conditions mentioned above.
Function of the O-ring
A direct-injection fuel injector has a gasket and an O-ring, as shown in FIG. 1 and FIG. 2. The O-ring prevents water, dust, and other foreign matter from depositing around the injector body. Too much deposits could harden due to excessive heat, and could make the removal of the injector a bit harder, but not really difficult if you have a high quality injector remover. You can search the internet to find a high quality injector remover. They may come in different names: injector extractor, injector puller, or injector remover. They all mean the same thing.
Function of the Gasket
The gasket prevents combustion gases from escaping into the injector body. If combustion gases get into the small gap around the injector body, corrosion on the surface around the injector body and on the cylinder walls could easily develop, and carbon deposits could accumulate in the gap very quickly.
When the carbon deposits in the small gap between the injector body and the cylinder wall hardens (which could happen in no time due to excessive heat), we are headed in for a serious trouble. The hardened deposits and the corroded surfaces of the cylinder wall and the injector body, combined, make a perfect locking mechanism (See Fig. 3). This makes the removal of the fuel injector extremely difficult. Referring to Fig. 3, see how difficult it is to pull out the injector with that cement-like carbon deposits locking the injector in place.
Why replace the O-ring and the gasket even if they seemed ok?
After some time of engine operation, the O-ring and the gasket become a bit hard and brittle. Moving the injector even just a little bit can break the seal that the O-ring and the gasket have provided. And because these sealing materials are a bit brittle by then, re-establishing the seal is difficult.
Combustion gases can now easily escape past the gasket, and into the gap around the injector body. This creates corrosion around the surface of the injector body and on the walls of the cylinder head. Then carbon deposits will start to accumulate to fill the gap. When the carbon deposits becomes hard, the injector will be locked in place and it would be very difficult to pull it out.
Whenever your fuel injector has been pulled out, turned, or moved even just a bit, be sure to replace the O-ring and gasket with a high quality replacement. This is to prevent the fuel injector from getting stuck. The cost of the O-ring and gasket is very small compared to the cost of removing a stuck fuel injector.
Of course, if you can find a solvent solution that could soften or dissolve the herdened carbon deposits, things would be a lot easier. So far, however, I haven't found a solvent solution that could dissolve the carbon deposits, and yet not harmful to the aluminum cylinder walls and the iron body of the injector. If you can find one, I hope you'll share some information on how I can have it.
"It may not be necessary nor practical to do things ourselves, but it's always nice to know how things are done the right way."
Victor Mangubat (author) from Philippines on October 24, 2012:
Thanks much, Novel Treasure, for your positive comment. This is all I need to strive hard to better improve my writing skills.
Novel Treasure from US on October 23, 2012:
I have to admit I don't know much about cars, but I was able to read and understand this hub. Very well written and easy to follow. Voted up and useful.