Auction Win or Mistake
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Joined: Dec 2018
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2010 GLK350
Auction Win or Mistake
Hi all i bought a c250 2012 with 81k miles the vehicle was a theft recovery that was a “no start” when i got the vehicle it was low on fuel added 2 gallons got her to crank but it was misfiring bad scanner the car just misfire codes. Oil did smell like fuel. Checked the plugs and coils they were bad and had oil. Did a compression test all was around 160 except cylinder one was 110. Changed the valve cover gasket put new oem plugs and coils fresh oil vehicle started up drives great but now it has a rough idle no check engine light but shows cylinder 1 misfire plugged scanner and it only shows one count of misfire when it first starts when driving the fault counter stayed at 1 engine light doesn’t flash don’t seem to have lose of power just rough idle at a stop or reverse. Also i noticed if i open the oil cap while the vehicle is running there is white smoke. No smoke from the exhaust. I’m kinda stuck could it be as simple as a vacuum leak, crankcase vent, bad injector? Any help is greatly appreciated hoping it’s not a cracked cylinder like i have read around. Thank you in advanced.
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
One cylinder low on compression test —> suspect head gasket. Iron cylinder liners are very unlikely to crack. That could also explain “white smoke.” What does the oil on the fill cap look like? Muddy/milky?
Other less likely possibilities that will be obvious when head is removed:
Burned valve
Poorly seating valve
Broken piston ring
Burned piston
None of those other possible problems mentioned would cause low compression.
Recheck that compression before disassembling engine.
Other less likely possibilities that will be obvious when head is removed:
Burned valve
Poorly seating valve
Broken piston ring
Burned piston
None of those other possible problems mentioned would cause low compression.
Recheck that compression before disassembling engine.
Thread Starter
Newbie
Joined: Dec 2018
Posts: 10
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2010 GLK350
Would bad fuel injector o rings cause the lower compression on the cylinder, the vehicle doesn’t really misfire over 1100 rpm mostly at lower rpms The motor mounts are differently shot, i drove the vehicle today the engine light turned on for cylinder 1 misfire and then cleared its self out. Thinking if injector o rings could have caused the lower compression. I’m no pro mechanic but i did work a lot on my Audis. I appreciate the input thus far. Does it seem like I’m going the right way ?
MBWorld Fanatic!
Joined: Sep 2013
Posts: 2,333
Likes: 689
2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
The o-ring is on the top of the injectors. The connection to the head is, I believe, metal-to-metal. But you have to get the common rail off to get to the head gasket, so check the cylinder 1 injector for signs of leakage. Note that the common rail must be reinstalled before rechecking the compression because it holds the injectors in place.
