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Diesel leaking into oil - how to source the leak?

GavDog

New member
Please forgive me, this is my first ever forum.
I have just recently acquired a lagoon 380 that has twin Volvo D1-30 engines.
One engine seems to be leaking diesel (I believe) into the oil. When I have checked the dipstick, the oil has been higher than the previous day + the engine has now raced out of control 3 times (only way to shut off was to block the air filter as even the manual shut off couldn't stop it) - very scary.
At first I thought it was a sticky throttle cable but after dealing with that and it happening again almost immediately + the oil being higher (when compared either both times cold or both times hot) I have realised it is something else.
The higher oil level and racing out of control engine both align with the theory that diesel is leaking into the oil somehow but I have no idea how nor how to narrow the leak it down. The injectors have been serviced with no change to the situation.
Any ideas? I'm desperate for help as we were meant to be beginning our summer voyage shortly and in Auckland it is almost impossible to get a mechanic that is available and willing to come to the mooring.
Thanks in advance for any help!
 
May be time to send the injection pump out for service.

Thanks for taking the time to suggest that. If it's not that, are there any other likely sources of the leak? It sounds like a tricky job removing the injection pump by looks of the workshop manual so I think I'll need to cover all my bases at same time.

Many thanks!
 
Thanks for taking the time to suggest that. If it's not that, are there any other likely sources of the leak? It sounds like a tricky job removing the injection pump by looks of the workshop manual so I think I'll need to cover all my bases at same time.

Many thanks!

If the engine is running away, the rack in the injection pump is hanging and the pump needs to be serviced. The pump can and will leak fuel into the oil.

I am sorry to say, there is no short cut or home remedy for this job. You can fix it right or destroy the engine with someones suggested shortcuts.
 
The pump looks fairly easy to remove. No special pullers.....

You will want to check the Mechanical lift pump, it also can be the cause of fuel getting into the crank case oil.
 
Thanks heaps, that's really helpful. Mechanic now booked in for Thursday and he'll check lift pump first too in that case. Fingers crossed its that as that seems a bit easier to replace as parts for injection pump are likely to be very hard to source at present. Thanks again!
 
Ok so the injection pump and lift pump have been replaced and the injectors serviced and tested and yet still diesel is filling the oil sump (approx 1cm of dipstick increase per 30 mins running engine). The mechanics have no idea what else it could be yet it is definitely doing it so we are stuck big time. Any other ideas? We are desperate. Thanks
 
Ps, could it be broken pistons and the injected fuel is bypassing the piston straight into the sump due to injector tip breaking and causing a hole in the piston crown? If so, how could I check the pistons without removal? Could a compression test be done easily or is there a way to see?
 
Ok so the injection pump and lift pump have been replaced and the injectors serviced and tested and yet still diesel is filling the oil sump (approx 1cm of dipstick increase per 30 mins running engine). The mechanics have no idea what else it could be yet it is definitely doing it so we are stuck big time. Any other ideas? We are desperate. Thanks

I'm sure you have worked it out by now, 6 months late. But just in case, I had the same thing and found a broken valve spring to be the culprit. I have also been told that a bent pushrod can cause the problem, as well. I have also seen a fuel leak at the injector leak past the injector and into the cylinder. This didn't seem possible but it happened. Hope this helps you or someone else.
 
I'm sure you have worked it out by now, 6 months late. But just in case, I had the same thing and found a broken valve spring to be the culprit. I have also been told that a bent pushrod can cause the problem, as well. I have also seen a fuel leak at the injector leak past the injector and into the cylinder. This didn't seem possible but it happened. Hope this helps you or someone else.

Thanks so much for replying. That's really helpful to know. Turned out that there was a pin prick hole in the injection pump and that the people that tested it actually lied to me multiple times and didn't actually check it properly. So massive expense and waste of time later that problem is fixed but now dealing with other issues it caused that haven't managed to suss out yet. Your discovery though is super good to know as the mechanics didn't ever mention a bent pushrod as a possible. Thanks again
 
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