27. July 2011 19:02
DT466e engines are very common and are fit in many kinds of trucks from propane trucks to ambulances. We work on a lot of these engines and overall they are very good performing engines and most customers seem to have good luck with them. Note I said DT466e and also note that the newer EGR engines are just called DT466 since this issue I'm going to discuss does not apply to the newer DT466s since the injectors are different on the new EGR engines. A common issue with the DT466e is a sudden loss of oil with no smoking and no apparent external leak. The most common cause of this is a failed injector O-ring. To understand how this occurs you have to understand how these injectors work. These injectors are fired hydraulically by high pressure oil. Below is a picture of one of the injectors we removed. There are 3 grooves for O-rings on these injectors. Note that at the top groove of the injector are 3 O-rings. This groove keeps the high pressure oil from leaking upward into the valve cover and a failure would cause a loss of injection pressure and possibly a no start. The next groove holds the pink O-ring. The pink O-ring keeps high pressure oil (which is in the area between the top groove and the pink O-ring) from going downward into the fuel galley. This O-ring is the one we are concerned with because if it fails it will cause the oil to be pushed into the fuel system and will cause the engine to lose oil and will contaminate the fuel supply. The next groove has the orange O-ring and this keeps the fuel from going downward to the tip of the injector and possibly leaking past the copper washer and into the cylinder causing extreme overfueling.
Since we suspected an injector O-ring failure the first thing we did was take a fuel sample. Here it is. This is what oil in the fuel looks like.
After taking the fuel sample we decided to pull all the injectors and investigate further. After pulling all 6 injectors we inspected the O-rings and found this. You can clearly see that the pink O-ring has failed on the #5 fuel injector and is the culprit for our oil loss. Just to note this customer was putting 4 gallons a day into the engine and this extreme oil loss came from ONE bad injector O-ring. We installed new O-rings on all 6 injectors and reinstalled all components. After test driving we noted no oil loss. A good practice would also be to drain the tank and fill with good quality fuel.
Thanks again for listening to me and hopefully this article will help you with future diagnostics.