gas in the oil

[navyboychad]

I have severl problems going on with my 1978 mercruiser. Its a GM 120. I have gas in the oil. Everything is leaning to the fuel pump. I did a presure test on the fuel pump and every thing was fine. I put in a new fuel filter and everything went wrong. the presure would hol at 2.5 on idle, and then drop to .5 as I increased rpms. I did a flow test and everything came out fine. I inspected the diapham in the fuel pump and couldn't find anything wrong with it. changed oil. took it out. oil psi was at 30 (norm) after the two hours of boating. it droped to 20 psi. and gas was in the oil again. there is a white froth on the oil cap, and on the dip stick. but when drained the oil is ok, except the gas smell in it. I assume the froth is staying on top and not draining when I chage oil. <br />I took the plug out of the bottom of the fuel pump and ran it. nothing came out. I figured that it gas would come out of there if there was something wrong with the fuel pump. what should I do?

 

[kussfamily]

Re: gas in the oil

If you have a hole in the diaphram,does gas have to come out of the clear line to the carb ?

 

[dmorley]

Re: gas in the oil

Is this a cam driven MARINE fuel pump?

 

[kussfamily]

Re: gas in the oil

its a cam marine fuel pump

 

[fireship1]

Re: gas in the oil

Hello, If you messed with the fuel pump and you feel that you have messed it up...replace it. But...Are you sure that your carb is not flooding your engine? Do you have any starting or running problems with this engine? These things might point to the carb. Let us know...we'll try to help!

 

[rkikenda]

Re: gas in the oil

If you see a white froth anywhere the oil is, then my bet is you have water in the oil. Gas will not do anything to oil except thin it. You will not be able to see gas in the oil. Check for warped head or cracked manifold. Those were my problem areas.

 

[kussfamily]

Re: gas in the oil

There is definitley a gas smell in the oil, and it is very thin, very light brown in color, white froth in the cover that you add the oil to. Can gas go from the carb to the engine via the vent from the cover to the carb ?

 

[Bondo]

Re: gas in the oil

You Need a New Fuel Pump............

 

[rkikenda]

Re: gas in the oil

When I had water in the oil due to overheat condition, it was causing the engine to struggle and die at low RPMs. This in turn caused gas to wash down the cynlinder walls into the oil. At first I had the exact same conditions you describe. The oil smelled of gas and I thought that was the only thing wrong. I had a topic posted on here with the same name "gas in the oil," but that wasn't the underlying problem. The white froth is definately from water and oil mixing.

 

[Yepblaze]

Re: gas in the oil

My thoughts.............<br /><br />The white froth on the cap and in the valve cover can represent excessive piston cylinder "blow by".<br /><br />One of the byproducts of combustion is water vapor which if excessive may manifest itself as froth.<br /><br />Now also consider if one or more cylinder is having problems sealing combustion enough to create excessive blow by, then during the compression stroke it will leak some of the air/fuel charge into the crankcase. This can produce the strong smell of gasoline in the oil.<br /><br />If available have a leak down test done on the cylinders. A compression check may indicate problems but a leak down test will actually test the rings sealing ability.