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Strong petrol smell on cold starts.

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Lately I’ve noticed a very strong petrol smell on cold starts. The smell is only noticeable outside the car and only on cold starts. It’s as if the engine is running very rich. Once the engine warms at all the smell goes away. The engine runs and pulls well when cold, not that I rev it much till it’s warm.

I’ve a suspicion that the ccv separator needs replacing but can’t see how it would cause this problem. I’m also believe that the tank vent is correctly attached as attached it when refitting the inlet manifold recently.

There’s no engine related faults currently logged (only drivers heated mirror fault). The only reason I’ve noticed the smell is that I’ve been doing a fair bit of work to the car so I regularly start it then get out to check all looks ok before closing the bonnet.

Any thoughts on whether this is normal and if it’s not where to look next to find the cause?

Plugs were changed about 3000 mile ago with ngk plugs being fitted.

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I wouldn't say you should be able to smell petrol. 

 

Check the fuel lines, could be something is slightly weeping when it's parked up for long times (cold start) but not when it's warm. 

 

CCV failing/leaking might let you smell oil/exhaust fumes, but I don't think petrol fumes.

 

Have you noticed a drop in mpg?

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21 minutes ago, 535i Andrew said:

I wouldn't say you should be able to smell petrol. 

 

Check the fuel lines, could be something is slightly weeping when it's parked up for long times (cold start) but not when it's warm. 

 

CCV failing/leaking might let you smell oil/exhaust fumes, but I don't think petrol fumes.

 

Have you noticed a drop in mpg?

 

To be honest I’ve not had the car long enough to notice any change in mpg. Added to that the fact that the constant stream of work that I’ve been doing to the engine which seems to be improving the mpg would make finding a leak hard to detect by mpg alone.

It does seem to be from the exhaust fumes which makes me think it could be running very rich when cold. There’s no smell of petrol when I’m outside the car before starting, it’s only after starting the engine.

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Hi.

 

Had this problem when I first got my old E60 530d two years ago.   It was fine until the cold weather came, then the fuel smell at start up appeared accompanied by ever increasing white exhaust clouds and needing to be cranked over for about 10 seconds before starting.   Everything cleared up as soon as it was running.  Mine was down to unburnt fuel  via glow plugs and controller which cured this.  Obviously not the source of your symptoms but worth checking what may be causing any unburnt fuel in the mornings.  This is the first car I have ever owned that hates frost.

Edited by oldjohnny

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9 minutes ago, oldjohnny said:

Hi.

 

Had this problem when I first got my old E60 530d two years ago.   It was fine until the cold weather came, then the petrol smell at start up appeared accompanied by ever increasing white exhaust clouds and needing to be cranked over for about 10 seconds before starting.   Everything cleared up as soon as it was running. 

 

Was advised that it was obviously unburnt fuel at start up and this was cured by replacing all glow plugs and the controller which was knackered.  No sign of anything since and mpg improvement evident.  May not be your source but worth checking out.   It's the first car | have ever owned that hates frost!

I think his petrol smell is from actual petrol... as in his car runs on petrol...

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Hi @oldjohnny sorry I probably should have put in the first post that the car is a 530i.

I’ve no issues starting the car and it seems to be running well. I do get a lot of vapour from the exhaust when the engine is not at full temp. I had been putting that down as steam but now think it’s a combination of unburnt fuel and possibly oil from the ccv.

You never smell petrol or burnt oil from inside the cabin if all windows and doors are closed so to me that rules out it coming from the engine bay.

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2006 530i is an N52, which I've never experienced personally. Could be normal, an old 3L petrol lump will likely smell a bit for the first minute, especially if you are down wind of the exhaust. If it's starting and idling smoothly, no fuel line leaks with no error codes then I wouldn't worry about it. Not CCV related.

The N53 does also smell a bit on cold mornings, luckily the wind direction is favourable to the orientation of the car on the driveway ;).

 

 

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@DarkHorse to be honest that’s my thinking as well but thought it worth checking with the collective mind to see if others have noticed this.

I think part of the problem is that we are discussing the one true fuel which seems to be a bit thinner on the ground than the devils fuel :-)

Edited by RandomName
Correcting typo

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Well, my exhaust is smelly on cold starts as well. Nothing amiss, runs perfectly, flies through MOT emissions when hot. I wouldn't say it is a petrol smell though.

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I think I might have found the cause of this. While changing the ccv oil separator last night I noticed that the map sensor on the inlet manifold was not connected. It must have gotten unplugged when I changed the DISA valve under the manifold a few weeks ago. This would tally with about the time I started notice the smell. It didn’t bring on any dash lights though.

I’ve scanned for codes since then but this was generally after some major work so just cleared them all and meant to check again after a few miles but never get round to it.

With the sensor plugged in there was a slight smell on starting but went away very quickly. Will know better once I take the car out for a proper run.

Lesson learned, check all sensors round the area you are working even if you didn’t disconnect them intentionally.

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I think when certain sensors fail or are indeed unplugged the engine will run but runs in a safer mode which is richer to stop any chance of stalling. MAF MAP lambda all do this if they fail in the "right" way... mpg drops no lights on dash but faults stored in the memory. Learnt this diagnosing my lambda sensor. Basically the sensors that help work out the fuel air mix.

Edited by Peggowski

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It'll be the emissions control dumping petrol into the exhaust to get the cats hot quickly. I wouldn't worry too much about it tbh provided there are no other untoward signs like horrific on fuel etc.

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@bmwmike I’ve not had the car in a steady state long enough from getting it to get a feel for the actual fuel consumption. In saying that my expectations are high on that front anyway :-)

Took it out for a quick spin and all seems well with the world again (Apart from the slightly slipping clutch that it).

It really does shift for a big barge.

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