Spitting petrol out of the exhaust??

[Ammaco]

My m42 318is is spitting a fair bit of un burnt petrol out of the exhaust. what exactly does this mean and how can i fix it? could this be costly?

[scottybeemer]

is it not condensation

[SwirlyE30]

Mm, where abouts is it? Ive only ever come across it being condensation, it might just smell a bit like petrol if its comming through the pipes.

[mrLEE30]

quite simply impossible that unburnt petrol can be comming out of the exhuast of a running car if the car is running ok- only possible case would be on a V engine with one entire bank of the V not running and if it was carb engine, and even then if the engine ran the exhaust would still get hot enough to burn the fuel that may possibly make its way into the headers.

Petrol contains a fair amount of water, this is burnt (actaully boiled) in the cylinder on the power stroke, it will then be ejected into the exhaust with the hot gasses, it will then form condensation toward the end of the exhaust system (ie the silencer area) as the pipes will be cooler. This condensation will eventually find its way to the end of the system and drip out as you can see. It is quite normal and seems to be a characteristic of Bosch injection systems, so you will notice it from Mercs too. It is also dependant on atmospheric conditions, so on days with a high relative humidity it will be more common.

hope that clears any doubts!


mrlee

[Turbo-Brown]

Think if you were getting raw petrol coming out of the exhaust, your engine would be inches from death as all that petrol will have washed the lube from a cylinder bore and a fair amount will have worked its way into the sump!

[mrLEE30]

Ahhh bore wash!!! not nice!!

mrlee