Leaky Injector

[Dazzajon]

Well, bit of a long story...


Just last week picked up a new to me boat. During the sea trail the previous week, the old owner was so tight he ran out of fuel in the port engine which he had to bleed the injectors to get started again. Anyway when I collected diesel was peeing out some of the injector feeds which I think I've now managed to fix but one of the injectors seems to be leaking oil from around it.



This is rather concerning and I really cant figure out where it's coming from, any ideas? Engine is a TAMD41B

[NoTies]

Are you 100% sure it is oil and not coolant? If it is oil I suspect what you will find is that it is spill from topping the engine. With engine running there is possibly a little compression leakage forcing the oil up and out of the injector tube. The first thing I would try would be backing off the injector clamp nut and re-tightening. If that doesn't work you may need to remove the injector, clean the sealing surfaced and fit new copper gasket.

[Dazzajon]

Originally Posted by NoTies

Are you 100% sure it is oil and not coolant? If it is oil I suspect what you will find is that it is spill from topping the engine. With engine running there is possibly a little compression leakage forcing the oil up and out of the injector tube. The first thing I would try would be backing off the injector clamp nut and re-tightening. If that doesn't work you may need to remove the injector, clean the sealing surfaced and fit new copper gasket.

I’m not 100% sure it’s oil but pretty sure. Looks, smells and feels like oil when I dip my finger in it. I’ve tried thoroughly cleaning the whole rocker cover just to make sure it’s not residue gathering there when engine heats up. Probably hard to tell from the photo but there is no sign of the oil running to where it’s gathered, it’s like it’s coming from around the injector. Is that possible?

[model 10]

You just need a new copper injector gasket. The black goo is combustion chamber leakage.

[DougR]

In all probability what you are seeing is a mix of the fuel that spilled when the injectors were bled, perhaps a little oil leaking from the valve cover gasket, and a bit of combustion carbon blowing by the injector. When the engine heats up this brew expands and pushes up around the injector.

The injector on the TAMD 41 engine sits in a copper tube which is pressed into the head with an O ring at the bottom and another O ring around the top of the tube to seal antifreeze at both ends. The exterior body of the tube is in direct contact with the antifreeze. Then there is a steel ring pressed into the head on top of the copper tube to keep the tube in place. This steel ring is what you see in the photo surrounding the injector where the injector disappears into the head. There is no oil in contact with the injector or the copper tube. The lower surface of the injector is sitting directly on the inner bottom surface of the copper tube, and this contact between the injector and the tube makes the seal of combustion gases. There is no gasket or washer of any kind under the injector.

If this continues to leak, the cure is to loosen the high pressure fuel line, remove the injector bleedoff fuel line and pull the injector. Clean the injector and the inside of the copper tube, paying attention to the condition of the lower seat on the inside bottom of the tube. If this seat is damaged it might be necessary to replace the copper, but that's probably not the case. If so, it's a dealer job as some special tools are required.

DougR

[a64pilot]

Take alcohol, and a tooth brush and a roll of paper towels and throughly clean everything.
Then see if it reappears

[jimbunyard]

I'd guess it's either residual fuel spilled or a seeping seal at the nut on the high pressure line. If someone fooled with the return line banjos for some reason, they could be loose or a washer could be compromised. If compression is leaking through the injector seat, typically it blows bubbles that are visible between the injector and the ring surrounding it when the engine is running. If the area is dry, squirt a little oil or diesel around the joint and leakage from compression will be evident.


Injector retainer nut torque is 18 ft lbs.


Injection line nut torque is unspecified; as little as possible without leakage is generally my goal.

[Dazzajon]

Thank you all very much for your suggestions. I shall try some the simple suggestions you’ve proposed first before calling in the expensive engineers!

It’s just bloody annoying as if the old owner hadn’t been so tight and ran out of fuel I wouldn’t have this problem - the survey came back with no engine leaks at all. Also as someone else has mentioned I don’t know for sure exactly what the old owner has done - he told me he’d had to bleed the injectors but I guess all it takes is for him to play with the wrong nut!