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Fuel contamination in oil

Gasoline is very volatile and evaporates very quickly, especially when heated to 200 degrees, the normal operating temperature of motor oil… For the oil level to rise on the dipstick, the fuel leak is pretty large and should be easy to find…I’m surprised you have not had a crankcase explosion. The conditions you describe are ripe for one…

I have not been using the boat much. I change the oil after about 10 hrs, just so I can use it here and there until I figure out this problem. The only theory is that one or more injectors is leaking after the engine is turned off. If I use the boat weekly, the fuel would have time to seep by the rings into the crankcase. Having the injectors tested at a reputable place convinced me that was not the problem. The injectors are over $200 each, X8, only available from Volve Penta. What a nightmare this has been… EZ

Just checking to see if my last reply went out…EZ

If you were leaking a lot of gas into the cylinders it seems you would get black smoke and blackened spark plugs.

Have you checked the vacuum hose to the fuel pressure regulator for signs of raw gas?

I think you need to check all of the other vacuum hoses to the intake manifold too.

Check the crankcase ventilation too. Make sure the PCV valve is clear and getting vacuum and the breather port is clear.

Circuitsmith,
The engine is running perfectly, with no smoke. I’ll check the vacuum hoses again, and the pcv valve again. Thanks, EZ

Where is the primary fuel pump supplying fuel to the injector rails located?? In a car, it would be electric, located inside the fuel tank. In a marine installation, it may be different. Is there any mechanical pump driven by the engine??

Have you investigated the area UNDER the intake manifold?? With some V8 engines, any liquids that accumulate there can leak past the “valley cover” and into the engine…

In most installations, the ONLY place gasoline is available to the crankcase is through the injectors or the fuel pressure regulator. There is no other path. Put a manual shut-off valve in that line.

Does the crankcase level increase when the engine is running or only when sitting for a period?? It’s hard to believe the problem occurs during operation WITHOUT OTHER SYMPTOMS unless there is another path for the gasoline to enter…

The fuel pump is electric, and is mounted on a bracket on the front of the engine. Your tip on the intake manifold has me interested. While consulting with the owner and service manager of the Volvo Penta dealership, he did come up with that possibility. I think that idea was dropped and we never followed up on it. What would we have to do, remove the intake manifold and visually look at the gasket and seal?
I have no way of knowing when the fuel is getting in there. With my recent engine, I checked the oil after every use of one hour. It seemed like the problem was gone, only to appear rather suddenly at about 12 hours. Because of no symptoms while running, my suspicion has always been after the engine is turned off.
I like your idea of a cut off valve! I had thought of that a while ago, then never did it as I kept thinking I would be able to find the source of the problem.
I’m leaving town soon for the week end so I’ll pick up on this agin on Sunday…EZ

Mechanics have told me that engines have come from the factory with piston rings installed upside-down and even missing altogether.
Unlikely as it might be, a rebuild could have a similar problem.

First, release the fuel pressure on shut down. Like your injected car, the injected fuel system stays pressurized.
I made that up, but it does seem a logical first step.

You need to check more than the PCV valve. I’ve seen where the valve was fine but the vacuum line leading to it was clogged.

EZ, In this forum, people can have input as long as they desire.
If anyone else has a problem similar to EZ’s, don’t hesitate to call in a mechanic. A fresh set of trained eyes may see what another doesn’t. It’s obvious, that the fuel delivery system is leaking into the engine, or fuel is going in, through injection, and not being burned, and ends up in the oil.

I am a mechanic. I’ve owned an auto repair shop for 30 years. The owner and service manager of the local Volvo Penta dealership cannot figure out what’s going on. They suggest I replace all the injectors, at about $225 each, times eight. I’ve had the injectors tested individually and they all test perfectly, spray pattern, etc up to 5000rpm. What would you do??? EZ

Just a couple of questions. (and keep in mind I’m not a marine mechanic; got enough headaches in life!)

How are the spark plugs burning? Clean tips?

The injectors were tested but do you know if they tested them for the possibility of any of them leaking off? Sometimes it may take a couple or 5 minutes before fuel starts dripping.

About the only things I know of that would cause oil to dilute this quick would be excessively rich running (again, plug tips), leaking fuel pressure regulator diaphragm, injector(s) leaking off, or an injector pulse width that is too long.
With the latter, you would think that would also show up on the plug tips.

Just throwing an odd one out there and keep in mind I don’t know how this boat is wired. When the engine is not running is it possible power and a ground could be provided to the injectors anyway and residual fuel pressure is being drained off into all of the cylinders due to the injector pintles remaining open?
On a hot restart this should come across as a flooded condition. After sitting for a bit some of the gasoline could have evaporated and some could have drained past the piston rings into the engine oil. This could allow the plug tips to burn clean.
Just a theory anyway since we’re grasping a bit.

ok4450,
Thanks for your response. I don’t know how long each injector was tested, probably not very long. I won’t get a chance to work on the boat engine until the end of this week. As well as checking the spark plug conition and fuel pressure regulator I thought of my own test for the injectors. I’m going to run the engine for a while, and pull out the fuel rails as quickly as possible,with the injectors still connected. I can check them with and without fuel pressure on them to see if any leak. More soon, EZ

How about just attaching a fuel pressure gauge semi-permanently to the fuel rail?

If an injector is bleeding fuel after shutdown the fuel pressure will disappear quickly, and you’ll have a place to start. Right now you’ve got nothing but guesses.

Good idea. The Volvo Penta dealership has supposedly run that test two times. They said it held pressure for about an hour. I need to run these tests again myself. I can’t trust what they said they did.
The engine is a harder to start warm and hot. It must have raw fuel in the cyls. Thanks, EZ

You are right about the explosion. I had a spark plug come apart, put a hole in a piston, caused a lot of smoke and then we had an explosion. It blew out the valve cover gaskets and the dipstick.