The video tells the story on the running condition of this MaxxForce DT diesel engine. International designed these engines to run on high pressure oil to hydraulically actuate each injector electronically by the on board computer which is separate from the fuel system which runs at 75 psi. This engine sounds like it’s running on one cylinder but in reality one cylinder is dead with way too much fuel entering the cylinder.
There were no engine codes and the fuel pressure / injection control pressure were normal. To start these diesel engines they need 75 psi fuel pressure and 800 psi injection control pressure (supplied by the high pressure oil pump). At first it was a mystery so we had to decide what to check first.
The only logical way to find this out was to pull all of the injectors for inspection. The #6 injector turned out to be faulty only because of a failed seal washer which prevents compression to enter the injector sleeve in the cylinder head. The high pressure and heat proved too much for the o-ring seal on the injector body which keeps the fuel supply contained. Once the o-ring gave way compression entered the fuel supply system to the injector and aeration went into effect.
This causes a severe miss since air compresses and proper injection comes to a dead stop. Even worse every time the engine is shut down fuel would run into the cylinder sitting on top of the piston until the next start up smoking out the exhaust and washing away oil lubrication on the cylinder walls. This was a concern and now that we knew what the cause was it was time to think of a solution so it didn’t happen again.
The photo above displays a couple of the injectors. You can see the bottom side of one of them is coated up with soot due to the compression leak. What is left of the washer is laying beside the leaking injector. The sealing washer slides over the tip of the injector and is supposed to seal compression from entering the injector cavity. To avoid this from happening again we thought about the parts used to seal the injectors.
They were aftermarket parts used out of the in-frame engine rebuild kit. (This engine was rebuilt a short time ago) We noticed the new seal kits we acquired from the dealer was a much better quality. So in the future we will go with original manufactured parts for injector resealing and apply loctite (threadlocker) to the injector hold down bolt. It has a torque of 22 ft lbs and must not loosen off or this kind of failure will happen again.
