I think my Fiesta ST is getting fuel contamination in the oil

[Hack]

2018 Fiesta ST. I have a 20-25 minute commute each way to work, so it should be getting plenty warm. The catch can is filling up quickly and it smells like gas. I also noticed the oil level seems to be increasing. It seems to run fine and power delivery is good (for what it is).

There's about 15,000 miles on the car. I recently had an oil change. It's possible they overfilled it, but I think fuel is getting in there.

I'm going to take it to the dealer, but looking for feedback here. I know there are a lot of knowledgeable people on this board.

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[sk47]

Hello; If you are getting fuel into the oil the most likely source would be a leaky fuel injector. At least that is what comes to mind. If such is the case two things come to mind. One is it can be potentially tested for. If the Fiesta has a schrader valve on the fuel injection rail the pressures can be measured. If the pressure holds for a while the injector(s) are not leaking. The engine does not have to be running. Turn the key on and in a few seconds the fuel pump will build pressure.
I am not sure of this but think the engine would stumble for a bit after first started and then clear up and run smooth if you had a bad injector leak. But this is not from experience, just thinks about it.

One note- there is a pressure relief valve which sends excess fuel back to the fuel tank. Under normal conditions the pressure relief valve keep around 60 psi of constant pressure. If the pressure drops this could also be a faulty pressure relief valve. This can cause the engine to not start right up.

The second thing is if the fuel leak is bad enough there is a remote possibility of a hydro lock. If enough fuel were to leak into a cylinder it could take up all the space and when the piston was on the compression stroke abruptly seize the engine. Has this happen on a Ford 428 cu in one time. It was not too much fuel but too much rain water. The air cleaner on the carb had a dished shape center. It seems the mechanic who serviced the engine di not tighten the thumb screw which held the air cleaner gasket in place. There was several days of rain while the bus was parked. The gap between the hood and firewall was positioned over the air cleaner. Rain had filled up the top of the air cleaner. The water made it's way down the threaded rod into the carb. Down the intakes into the cylinders. When I went out to start it the engine fired on a couple of cylinders but when one piston was stopped in the compression stroke it locked the engine. Had to have a new engine put in.
When i got it back there were two rubber washers under the thumb screw on the air filter cover. They made me park on a flat spot and not on a hill which did not make sense. Any way it was a county school bus and I was not out of pocket. I do not think you are in much danger of this as fuel will evaporate and it is hard to picture enough leaking down.

Keep in mind I am just making a WAG and not a guess I have confidence in.
Good luck.

 

[Hack]

Thanks a lot for the info. I have a fuel pressure tester, so I could hook that up and see if it's holding. I did look on some Fiesta forums and some people have had problem with the gas tank evap system causing issues. However, I haven't noticed a pattern with rough running after fillups, which they said typically happens in that situation.

 

[Shifting_Gears]

Thanks a lot for the info. I have a fuel pressure tester, so I could hook that up and see if it's holding. I did look on some Fiesta forums and some people have had problem with the gas tank evap system causing issues. However, I haven't noticed a pattern with rough running after fillups, which they said typically happens in that situation.

I had a Focus ST and had evap issues. It caused the car to run super rich. I didn’t notice any fuel dilution in the oil but wouldn’t be surprised if it happened. It was rich enough the engine would try to stall at idle and the cat smelled like it overheated due to too much raw fuel burning off in it.

I replaced one of the evap hoses in the engine bay and it greatly reduced the issue but didn’t 100% return it to normal. I suspect there was issues with the fuel tank evap as well.

 

[Hack]

It should still be under warranty, so hopefully my local dealer can fix it.

 

[sk47]

I had a Focus ST and had evap issues. It caused the car to run super rich. I didn’t notice any fuel dilution in the oil but wouldn’t be surprised if it happened. It was rich enough the engine would try to stall at idle and the cat smelled like it overheated due to too much raw fuel burning off in it.

I replaced one of the evap hoses in the engine bay and it greatly reduced the issue but didn’t 100% return it to normal. I suspect there was issues with the fuel tank evap as well.

Hello; there was a discussion on one of the TV automobile shows not long ago. Maybe the PBS show Motorweek. Any way the crux of it was that in the past you could buy components of the evap systems which were prone to fail. Valves and such. It seems that now these components are built into a larger unit and you must purchase the entire unit if one of the valves begins to leak.
Sort of reminds me of the demise of rubber inserts for windshield wipers. I use to by the rubber inserts and would replace them . Now I have to buy a whole wiper assembly which is just morre stuff in a trash bin.

 

[Shifting_Gears]

Hello; there was a discussion on one of the TV automobile shows not long ago. Maybe the PBS show Motorweek. Any way the crux of it was that in the past you could buy components of the evap systems which were prone to fail. Valves and such. It seems that now these components are built into a larger unit and you must purchase the entire unit if one of the valves begins to leak.
Sort of reminds me of the demise of rubber inserts for windshield wipers. I use to by the rubber inserts and would replace them . Now I have to buy a whole wiper assembly which is just morre stuff in a trash bin.

Yes, that sounds about right!

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