Fuel leaking into the sea from my exhaust

[DavidMRea]

Hello
I'm new to this forum - and hoping someone can suggest solutions.
This has only just started happening - When I run my engine (Yanmar 3GM30F) I seem to be polluting the seas with diesel at the same time.
The engine is a little harder to start than it used to be, and it doesn't sound like it's running smoothly.
There's also some diesel fuel getting into the bilges.

If it's misfiring for some reason, would there be excess fuel in the exhaust?

I've checked all the fuel lines to the engine and they're all dry.

Any clues, anybody?

[rbk]

Might be time for a top end job.

[Hesti]

Sounds like poor compression on one cylinder or serious issues with the injection timing or at least a worn injector or the high pressure pump is going or ...


Doesn't completely explain the fuel in the bilge though. Can you see where the engine is leaking the fuel?

[Sailmonkey]

Look for a thread by sailorchic. She had the same engine that was hard to start and ended up being a cracked piston ring land.

[sailorboy1]

cracked head is my guess unless then really is more than one problem.

[Cheechako]

Possible the 3gm cracked piston issue. Mine would run but start a bit hard and not run to full rpm or power.
However, it could very well just be a bad injector. They often go bad just because they sit without use, the tip gets fouled. Then it streams fuel instead of atomizing the fuel and goes out the exhaust. Maybe remove the injectors and have them tested and rebuilt, not a bad thing to do anyway and not too expensive.

[motion30]

We go right to a cracked piston ?
It seems more likely he would have a bad fuel injector

[cyan]

I would spend some time finding out how the fuel got into the bilge since the fuel lines are reportedly dry. Check the low point of the exhaust hose after the mixing elbow. If the fuel is simply getting from the exhaust into the bilge, then yeah- focus on the injectors. If the fuel is coming from somewhere else, THEN go down the bad news (expensive) list.

[rbk]

Originally Posted by motion30

We go right to a cracked piston ?
It seems more likely he would have a bad fuel injector

Yup. Injectors, timing then valves. If you get that far you’ll be able to check your cylinders as well.

[captstu]

How is the oil? When my 3gm’s cracked several pistons, blow by went up, fuel entered the oil and the bilge via blow by hose

[DavidMRea]

Thank you, everyone
My oil was ok, but I’ll check it again.

Thanks

D

[scallowayuk]

I had the same problem.it was a burnt out valve.injector was pumping fuel into the cylinder but no compression so fuel dosnt ignite flows out exhaust .possibly broken ring but more likely burnt exhaust valve.

[Steve 3]

Stressful right..

Here is a bit of simple trouble shooting you can easily do that will help you/ us guide you.

Diesels don't misfire they fail to combust. So there are not that many reasons for this as it is usually mechanical.

A quick check for cracks or compression issues:
Shut your fuel supply to the pump/injectors.
With a fully charged battery crank the engine for say 10 seconds.
Listen to how it spins, is it even or does it speed up and down, as in an uneven speed.
Do this twice allowing 2 minutes for starter to cool.
If it seems even in speed of spin/rotation then compression is assumed to be equal on all cylinders. (this is call a compression comparison check)
If it isn't then you have what we refer to as a base engine problem.
If it is just an injector then try this: Dump the fuel from the fuel filter and replace it with an injector cleaner such as, Seafoam, or whichever you prefer.
Start the engine (fuel on) and run for 7 minutes, then shut it down and allow to soak over night, then repeat this process again.

Now for the leak in the bilge if you can't find it through inspection then delay this till you perform the above.
Diesel in the exhaust suggest leaking injector (s)

[sazarac]

Pull the injectors and get them serviced. While they are out run a compression test.

[DavidMRea]

I am reluctant to run the engine while it's leaking fuel. Boat is moored in a sensitive estuary environment.
But it seems there's no way around that!