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#1
11-26-2007, 10:34 PM
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W116 M110 owners w/ 4bbl carb, Beware
This weekend I drained the oil from the M110 engine. (The car is stll on jackstands, waitng for caliper rebuild(s)).
It had the Solex 4A1 carb before I installed the Weber. And when I removed the Solex, there were small puddles of gas inside the intake manifold. Well, what drained out could best be described as 5w oil, smelling like gasoline. I can hypothesize that as the Solex was spewing gas into the cylinders, and any oil consumption was hidden by a steady volume of gasoline. This scenario gives the owner the impression the engine was not using oil. The quality of the German steel contibutes to the good compression numbers (143-154 psi cold, throttle closed). The cam lobes amd timing gears look above average for a 200,000+ miles. The previous owner was a 70 year old man; hopefully when the carb started spewing gasoline, he decided to sell the car to me.
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1970 280S M130 engine- good runner 1971 250 M130 engine- #2 rod bearing, gone 1971 280SE (blown engine,parts car) 1977 German 280S W116-only 33 years old 
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#2
11-27-2007, 09:17 PM
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Learned something else today
I talked with a mechanic, and he said the likely cause is a worn mechanical fuel pump that allows gas to enter the crankcase at the plunger interface. He said the older Chevy 6 cyl. engines would have the same problem when their mechanical fuel pump would fail.
This make more sense to me, because the oil level was correct when I bought the car in July. And, for the last month, an oil/gas mixture has been below the fuel pump. I suspect the pump has gone bad. I don't think the Weber is spewing gas, since the engine revs easily, like a motorcycle, and it's crisp. I just now lowered the rear of the car to 5" off the ground and jacked up the front to 14". Since all the old oil is drained, I figure if a mixture leaves the oil drain plug when removed, this fuel pump theory will be confirmed.
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1970 280S M130 engine- good runner 1971 250 M130 engine- #2 rod bearing, gone 1971 280SE (blown engine,parts car) 1977 German 280S W116-only 33 years old
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#3
11-28-2007, 10:06 PM
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except that the gasoline draw might only happen during a vacuum condition in the engine. -CTH
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#4
11-28-2007, 10:21 PM
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I haven't removed the fuel pump yet
But I plan to this weekend. There is an inspection cover that probably gains access to the screen.
cth350, your cryptic reply leads me to believe that somehow the lower crankcase pulls vaccuum from the easiest source. I am not familar with any crankcase 'venting' to eliminate this vaccuum. The fuel pump probably delivers plenty of volume, for both driving and dumping gas into the crankcase. Unless a person noticed poor fuel mileage, or thinner oil, smelling like gas, then a fuel pump failure could be remain hidden?
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1970 280S M130 engine- good runner 1971 250 M130 engine- #2 rod bearing, gone 1971 280SE (blown engine,parts car) 1977 German 280S W116-only 33 years old Last edited by MunichTaxi; 11-28-2007 at 10:21 PM. Reason: correction
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#5
11-29-2007, 12:17 AM
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Yup, that Solex is a pile. I'm about a step shy from going to the Holley conversion kit.
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I'm not a doctor, but I'll have a look.  '85 300SD 245k '87 300SDL 251k '90 300SEL 326k Six others from BMW, GM, and Ford. Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]
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#6
11-29-2007, 07:22 AM
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Take that puppy on a long drive.....
...If you have gasolene dilution of the oil, the level may stay high around town. But, take a trip where the oil gets hot enough to boil off the gas, and you could see a dramatic drop inthe oil level. No blue smoke, nothing noticable while driving, but a big drop in level.
Jim
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14 E250 BlueTEC black. 45k miles 95 E320 Cabriolet Emerald green 66k miles 94 E320 Cabriolet Emerald green 152k miles 85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles
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#8
11-29-2007, 04:50 PM
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"gasoline to run down the side of the engine"
 jeezus, does that shock anyone else? If you are interested in an electric pump, I recommend a nice silent carter available readily at any online speed shop (jegs.com/etc) I bought one and it's well made and works flawlessly. It'll keep your fuel temps down and deliver a nice steady psi which is handy in the summertime.
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___ /<>/>/> 1967 230S automatic Boston, MA
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#9
11-29-2007, 05:47 PM
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[quote=todds;1688873]"gasoline to run down the side of the engine"
quote] A functional fuel pump will not leak a drop. Fuel leaking out of the weep hole is a sign the fuel pump is faulty. Nothing to make ones I bug out.
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#10
11-29-2007, 10:17 PM
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Update on progress....
The fuel pump has a weep hole that allows any leaked gasoline to run down the side of the engine and not contaminate the oil.
I removed ther pump tonight, and tore it down to the diaphragm. There are 1/32" long radial cracks aound the circumference of the diaphragm. I found the weep hole, which was probably the cause of seepage. It sure seemed like there was a lot of gas in the oil; I have only run the engine 30 minutes since the Weber install. So, I'll start with a new mechanical (or electric) fuel pump. I should rebuild the used Weber carb I installed; otherwise I could ruin 6 quarts of new oil.
__________________
1970 280S M130 engine- good runner 1971 250 M130 engine- #2 rod bearing, gone 1971 280SE (blown engine,parts car) 1977 German 280S W116-only 33 years old
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