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MG MGA - oil turning black, smelling like gas

Hi,

I just pulled my engine so I can get the car painted. Before I pulled it, I had one piston that wasn't firing. I figured it was the carbs because there was a lot of black smoke. Also, the distributor cap popped off, so maybe that was damaged. I just had the cylinder head worked on, so I'd be surprised if it was one of the valves unless I did sometime wrong.

Anyway, this is my question. I drained the oil out, and it was really black and smelled a little like gas. This oil only had maybe 20 miles on it, though I idled it a few times before I drained the oil to try to figure out what was wrong. Any idea as to what could be causing this?

Darian Henderson

By "this" I meant the oil turning black.
Darian Henderson

Hi Darian. It is very likely that a carburettor or carburettors are runnng too rich. This could be from an improper mixture setting at the carburettor jet or jets. It could also be an incorrectly adjusted choke mechanism. Either way, it appears that the motor oil is being diluted by gasoline, and this can cause serious wear to the cylinders and bearings! You might want to re check your carburettor jet settings to ensure that the mixtures on the carbs are not too rich. If the carb justs are adjusted properly, then it is quite likely that the choke is incorrectly adjusted, and one or both of the chokes is esentially staying on all the time, even when the choke know is fully in. When the choke knob is pulled out, both carb jets should be pulled down by the choke levers. When the choke button is pushed all the way in,the jets should rise fully. If the jets remain partially down when the choke knob is all the way in, then the choke is out of adjustment and needs some tweaking. hope this helps, Glenn
Glenn

Thanks, Glenn, I appreciate it. I forgot to add that I was planning on getting the carbs worked on anyways, but I was just trying to figure out what could cause oil to do this. Is there any other possibility than the carbs?
Darian Henderson

The piston not firing was the problem. The fuel meant for that cyl was washing down the cyl wall and ending up in the oil. Any thing that can cause a miss can cause excess fuel in the oil. Of course if the miss is caused by an over supply of fuel the symptoms are greater. A compresion test taken on an engine that is full of fuel could be misleading.
Pull the plugs change the oil and filter and dry out the engine. Then oil down the cyls to protect the engine or it will rust. Once dried then oiled a compression test will have meaning. The starter can be bolted to the backing plate out of the car to check compression. I would not want to reinstall the engine only to pull it after diagnosis.
R J Brown

Thanks. I've already drained the oil from the oil cooler and engine. I'll squirt some oil down the cylinders with a turkey baster this weekend.
Darian Henderson

This thread was discussed between 07/05/2007 and 08/05/2007

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