2007 C70, car will not start without removing the oil fill cap, once car starts smoke billows from oil fill, a lot! if you put oil filler cap on engine dies, cannot start with cap on! 2.5 T5
any help is greatly appreciated. PS i replaced the oil filter housing (oil trap assembly, no difference

 

well the PCV / oil separator connects the crankcase to the intake to allow blow by gasses to be burned. By removing the fill cap you are allowing the crankcase pressure/gasses to vent. If the oil separator fails, it can allow oil to get into the intake and on a turbo car, it can create an air leak. I'm wondering if the oil separator was installed incorrectly or has totally failed. I'm also wondering if you have some serious issue going on where your car would smoke or create a lot of pressure in the crank case. Have you done a wet/dry compression test to test the rings and do you have any other signs of a failed head gasket? Try this - start the car with the fill cap off. place your hand over the opening - do you feel pressure out or in?

 

car will not start with oil fil cap on, take cap off and start engine and it looks like a steam locomotive, spewing smoke and oil , will do compression test in AM Thanks

 

spewing smoke from the fill cap? have you noticed a sweet smell (typical of coolant getting into the combustion)? Anything white or gray coming out of the exhaust?

 

To me sound like a failed PCV that was left for a long time , which unfortunately can be terminal , did the car make a whisling noise before ? and removing the oil filler cap or dipstic stop it