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CGI petrol in oil

Shelbygt350

New Member
Joined
Sep 5, 2019
Messages
16
Location
UK warrington
Car
C class CGI estate
Hi just joined.thanks for letting me join.I had a silk last year.but just bought a c class CGI 1.8 petrol runs perfect.but has a problem with petrol getting in the oil.The dealer I bought it off had engine rebuilt because of tapping.Got the car back and petrol is back in the oil.I changed the high pressure Feul pump because it runs of the camshaft at the back off the engine.Still getting petrol in the oil.No fault codes all clear.Any one any ideas.cheers mark
 
Petrol in the oil on direct injection engines has been a known problem in the auto industry. Some manufacturers have the problem licked and some don't but I hadn't heard of MB having the problem before. The engine may be over fuelling for some reason and the excess fuel is getting past the rings and into the sump. That will need to be addressed. In the mean time it will need frequent oil changes to prevent engine damage and I would choose the thickest oil in the MB approved list to minimise the effects of fuel dilution.
 
http://www.autocats.ws/manual/sdmedia/mediadb/mb_Acrobat/einf/m271/2009_05_001_001_en.pdf
Have you had the car on STAR to check for any fault codes?
One thing that occurs is that if the valve timing was off [mechanically] it might not show up as a fault code. I believe camshaft timing is crucial on these CGI engines- that's why MERC use a toothed timing chain arrangement rather than the open chain and sprocket arrangement? I expect there's a way to visually check this basic timing via marks on the associated mechanical components but I'm not privy to that info sorry think you need a special bolt on jig for this?

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As 190 says, the petrol is getting from the combustion chamber past the compression ring and the oil scrapping rings into the oil.

Check also the thermostat, the engine might not be warming up and running cold?
 
This morning it started backfiring.so parked it up.so could be timing.the dealer Belgrave garage doesn't won't to no as he has spent lots on it.but still the same problem.
 
Read some were you can alter the Feul mixture .

I doubt very much that that is the problem.
As per two earlier suggestions, thermostat (which will influence the fuel mixture) and the cam timing which appears to be a known issues and, as the engine has been apart - suspect.
Even then, I'm more inclined toward raw fuel on the cylinder wall being at the root of this through either a badly spraying injector or some failed interaction with the incoming air stream that is preventing correct mixing of the fuel and air and atomisation of the fuel.
The above assume ingress to the sump from above. But as you have already changed the HP pump, unlikely it is leaking fuel directly to the oil though if it is easily accessible I'd be tempted to remove it and check the sealing arrangements just in case.
 
Hi thanks for replies.this morning car was banging like it was back firing.stopped check oil etc.did it once more on way home only half a mile away.tonight started it and seemed ok.something major.taking the dealer to court now had enough..Seems like it's had this problem for a while and nobody knows what it is.
 
As a matter of interest, OP, is this the M274 engine?

Ernie
 
Hi thanks for replies.this morning car was banging like it was back firing.stopped check oil etc.did it once more on way home only half a mile away.tonight started it and seemed ok.something major.taking the dealer to court now had enough..Seems like it's had this problem for a while and nobody knows what it is.

Do you think discussing it in a calm manner with the dealer (who has already had the engine rebuilt so clearly takes their responsibility seriously) rather than issuing threats of court action might bring about a better result?
 
Hi it's a t model I think CGI c180 w204
That would be the M271 engine.

As others said, timing issues on M271 could spell a fatal engine fault (which, may not only write-off the engine, but the entire car if it's old).

Hopefully the people who reconditioned the engine also replaced the timing gear (camshaft sprocket wheels, timing chain, tensioner and guides).

Either way you want this diagnosed asap. I wouldn't drive the car any further. If you are lucky then it will only be a fuelling issue (injectors, fuel pump, etc), or misaligned timing.
 
As a matter of interest, OP, is this the M274 engine?

Ernie
On the C-Class, the M274 engine was 1.6L on the W204, and 2.0L on the W205.

There where 1.6L and 1.8L variants of the M271 engine, but there was never a 1.8L M274.

So if the OP has a 1.8L CGI engine, then it must be an M271 (with the dreaded timing gear issue).
 
They did the timing chain and cogs.then the engine starting tapping.they rebuilt the engine ground the crank as bits of metal in the oil.was told it's the chain catching the side of the block.also changed the bottom cog and tensioner.aweek later back to petrol in oil.its being going on now since Feb.Damas don't now what they are doing.told them on a few occasions petrol in oil.dealer has paid to have work done.but the same problem is still here so rejecting the car and going court if I have to.seems like the CGI engine is a bad engine.any one else have these problems?
 
The only comment I have to make is that it is unusual (though not entirely unheard of) to repair an M271 engine that was damaged due to timing gear failure, because in the majority of cases it is not economically viable.

If it's (say) a late, low-mileage, C250 CGI, then it might be worth having it fixed, but otherwise it usually isn't.

I am speculating that they may have cut corners when carrying-out the engine rebuild, especially if they were working to a budget on the dealer's instructions, though I obviously don't know this for certain.

Either way, by the sound of it, this 100% an issue that needs to be resolved by the dealer.
 
Your car seems to be overfuelling as several others have said. This could be down to several reasons. The fuel injection system is described on pages 18-20 of the pdf I posted earlier. As you can see there are several components which might give rise to excess fuel entering the engine. This could vary from mistimed injection/ or valve operation to stuck/leaking injectors or the fuel rail being over pressurised? My eye was drawn to component b4/6 the fuel rail pressure sensor has anybody monitored the system in operation in real time [ live data] using the MB diagnostic system? Sometimes fault codes are not enough on their own.
 
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On the C-Class, the M274 engine was 1.6L on the W204, and 2.0L on the W205.

There where 1.6L and 1.8L variants of the M271 engine, but there was never a 1.8L M274.

So if the OP has a 1.8L CGI engine, then it must be an M271 (with the dreaded timing gear issue).

Sorry, should have noticed that it was a 1.8 engine. I had 2 1.6 M274s and they were both good apart from a t/stat on one of them.

Ernie
 

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