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Gas in the engine oil

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kash311

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I have a 2004 Starcraft Aurora 2210, with a Volvo Penta 5.0 GL-D - Carburated engine and raw water cooling system.

Having a couple problems. First, the engine overheats at/above 3500 RPM's. Below that it runs great, and at normal temp (160). If I let it run at 4000 (or so) RPM's the temp rises - eventually to max (horn). If we bring it back below 3500 RPM's the temp will drop back to 160. Installed new impeller (old one was fine), and a new thermostat (old one seemed fine). I'm still working on this problem, but have another problem as well. Didn't know if they could be related.

I'm getting fuel in my oil. I first noticed this when I got some lifter noise at high RPM's. It would go away at low RPM's. Checked the oil and it was WAY high. Almost 3 quarts more than what I filled it to - Just above the add mark. It smelled like gas and had no viscosity all all.

Changed the oil/filter with Volvo SAE 30 synthetic - Ran it a few minutes - Then changed both again. Once again, I filled it only to just above the add mark (approximately 4.5 quarts). After about 2 hours of run time, the oil level is well above the full mark and smells like fuel again. It's not milky at all, so I expect it has nothing to do with water.

Any ideas how fuel could be getting in the oil? The engine has about 300 hours on it and has been well maintained. No other problems to date.

Thanks for any feedback.
 
Does this engine have mechanical fuel pump or electric? If mechanical, the diaphram in the pump could be bad, leaking fuel into the oil. Other than that, I would think it would have to be an intake manifold or gasket problem.
 
I guess it could also be bad rings. Check for excessive "blow by". Remove the Oil Filler cap while running and see if pressure blows out.
 
I've not tried that, but will. I have done a compression check though and all appeared normal. On a warm engine all cylinders were between 170 and 180. Not a great compression gauge (it was the press on type - not threaded). Also, I didn't do it with the throttle open - Read later that I should have. I'll do another the correct way, but wouldn't I see some smoke in the exhaust (burning oil) if the rings were shot? Just thinking out loud...
 
I had the same problem - look for "Weber Conversion - a word of warning" further down the page. The problem you have is almost certainly down to excess fuel pressure between the fuel pump and the carb. It's maybe an issue with the needle valve on the float, meaning that the float sticks open and the fuel floods through the carb into the sump. A strip down and clean would maybe sort this, but I'd recommend getting an adjustable fuel pressure regulator and dialling back the pressure to where it doesn't flood. you can see this by removing the flame arrestor and (when choke butterflies are open) looking down the venturies at idle. If you see fuel running down these, then the pressure is too high.

As for the high temps, if your oil is diluted by fuel then you have no viscosity in the oil, meaning ( I would think ) that friction and therefore temperatures would increase. Don't run the engine until you have diagnosed the problem. I've ended up with a full engine rebuild and the loss of three seasons boating due to fuel in the sump causing a bearing failure.
 
HOLD ON< a 2004 with a factory electric fuel pump has the fuel pressure set up, just check it, there is no reason to buy some aftermarket regulator. 2nd, get a manual. you could have many things contributing to gaining oil, from a bad spark plug to leaking well plugs in the carburetor. start with the basics, check your fuel pressure and compare it to factory specs, check your cap/rotor and wires for arcing, change your plugs, look down the carb with the motor running, see if your have fuel dumping to the center of the carb from the bowl breather. start with this, there is no reason to modify what the factory built, just find whats wrong with your setup.
 
Agree! Stay with the OEM components and make them work correctly..... of which may mean replacing some of them!

Since this is an electric fuel pump, the pump contributing directly to the fuel in the oil, is almost remote..... in fact, a very unlikely candidate, unless for some reason the pressure is way above normal, and the needle/seat are not capable of checking this.

I'd be more inclined to think that continued fuel supply with a leaking needle/seat is more likely the cause.
However... this would require more than a few cycles of run/shut down, etc.
That's quite a bit of gasoline you're talking about.


Questions:
If the fuel pump shutting off when the engine is shut down?
As mentioned, when shut down, are you able to see fuel being dumped into the carburetor throat?
Is this occuring more so when the engine undergoes several starts/stops?
Or this occuring during one continuous run cycle?

Either scenario may help you determine which is contributing to the unwanted fuel supply and eventual oil contamination.
IOW, if the oil is becoming fuel contaminated with one continuous run..... then you may have an excessively rich or malfunction scenario.
(normally, an engine will not run very well under these extreme rich conditions)
If this requires several runs.... and several shut downs..... then I'd lean more towards continued fuel supply and/or needle/seat issues.

Like said..... that's one hell of a lot of oil contamination.
 
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