Fuel in motor oil!
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Senior User
Joined: Feb 2008
Posts: 184
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From: League City Texas
Fuel in motor oil!
Hello fellow Gurus,
This past week I replaced the rear main seal on my 79 f 150 351m. As I took my oil pan out I noticed the smell of fuel in the oil. The oil had a heavy mixture of fuel in it. I have been experiencing starting issues the past couple weeks to the point of full battery drains just trying to start it. The first thing that came to mind was to check my carb. As I open it up the carb was bone dry in regards to fuel. Could this be the root cause? Any other ideas? Thanks
This past week I replaced the rear main seal on my 79 f 150 351m. As I took my oil pan out I noticed the smell of fuel in the oil. The oil had a heavy mixture of fuel in it. I have been experiencing starting issues the past couple weeks to the point of full battery drains just trying to start it. The first thing that came to mind was to check my carb. As I open it up the carb was bone dry in regards to fuel. Could this be the root cause? Any other ideas? Thanks
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Senior User
Joined: Feb 2008
Posts: 184
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From: League City Texas
GFW,
Shouldnt the carb hold fuel? When I pulled the carb out i did see fuel inside the motor through the manifold. This leads me to believe that fuel is getting up to the carb. Will a fuel pump with a bad diaphram still pump fuel up to the carb? Thanks
Shouldnt the carb hold fuel? When I pulled the carb out i did see fuel inside the motor through the manifold. This leads me to believe that fuel is getting up to the carb. Will a fuel pump with a bad diaphram still pump fuel up to the carb? Thanks
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Depending on how bad the hole in diaphgram is, yes it will still pump fuel to carb. Fuel should stay in carb till it eventually evaporates. If it doesn't, fuel could be leaking out into intake, cylinders and into oil. My first post was based on no fuel, dry carb.
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
The fuel pump has "weep holes" engineered into it's design to help avoid this but over the years these can clog up forcing the fuel to go into the crankcase.
Replace your fuel pump and the oil dillution will go away and the hard starting should go away too.
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Senior User
Joined: Feb 2008
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From: League City Texas
GFW,
I believe that fuel is leaking into the intake from the carb. I could be wrong but like I mentioned, inside the intake manifold there were traces of fuel. I soaked 2 or 3 shop rags when i stuck them inside the intake. Could the float be bad on the carb? Should I change the fuel pump just in case?
I believe that fuel is leaking into the intake from the carb. I could be wrong but like I mentioned, inside the intake manifold there were traces of fuel. I soaked 2 or 3 shop rags when i stuck them inside the intake. Could the float be bad on the carb? Should I change the fuel pump just in case?
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Senior User
Joined: Feb 2008
Posts: 184
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From: League City Texas
Mike,
So, it seems like the culprit might be the fuel pump. My dad is rebuilding my carb today. He seems to think that the fuel is leaking through the carb into the motor. Maybe we have it wrong.
So, it seems like the culprit might be the fuel pump. My dad is rebuilding my carb today. He seems to think that the fuel is leaking through the carb into the motor. Maybe we have it wrong.
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Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Float stuck open and continualy cranking will force fuel into intake(flooding). Depending on carb, and I don't know the internal workings of all, there could be a hairline crack in it allowing bowl to empty in to manifold. You could test fuel pressure from pump and get some idea on it's condition. Should have 4-6psi. You obviously have carb off, so good time to rebuild it and check fuel pressure. Carb will put gas into oil, but usually the problem is fuel pump.
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Thread Starter
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Senior User
Joined: Feb 2008
Posts: 184
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From: League City Texas
Thanks GFW and Mike! Fuel pumps are inexpensive so I might change it out and rebuild the carb. Hopefully the problem gets resolved! By the way carb is a motorcraft 2 barrel.
Believe Nothing
Joined: Jun 2004
Posts: 7,514
Likes: 398
From: W. Central FL.
