Petrol smell in 996

[garrymon]

Hi

I'd be very grateful if anyone could help me with a problem that has stumped two mechanics.

I own a 2001 996 Carrera 4 Cabriolet. For about 12 months, there has been an occasional petrol smell in the car. At first, it mainly happened when I started the car in the mornings, as if the fumes had been building up somewhere overnight. It also often seemed to happen when I braked or accelerated sharply.

I took the car to my local garage who did the following:
Changed oil
Changed oil, air, fuel and pollen filters
Changed the plugs

This reduced the problem a bit, especially the smell on first starting the car in the morning, but did not deal with it fully.

I then took the car to a specialist Porsche servicer in St Albans, called Jaz Porsche. They ran a full check for leaks but could find none. They then did the following:
Changed fuel tank cap
Changed expansion rivet
Changed bleeder valve

Again this had some impact but didn't solve the problem.

Recently the problem seems to be get slightly worse as the petrol tank empties.

I haven't taken the car to a main dealer as I've always found my local dealer to be pretty useless in fixing faults in the past.

Garry

 

[G7TTR]

Garry if JZM can't find a leak I doubt a main dealer will. I take it there is no smell of petrol outside the car or from the engine when running? If there is no leak from the system, could it be that a previous owner has split petrol inside the car? I know it's a long shot but maybe worth checking the carpets and rear seats. Mike

 

[Richard_Hamilton]

Welcome Garry! Jaz are well respected as Mike says, and I doubt a main dealer would have done better for this type of problem. It sounds to me like it might be a problem with the carbon canister (evaporative system) which is located in the front wing, near the filler neck. Is the smell coming from that area?

 

[SteveAndrews]

I know you have said the fuel cap was changed but it may be worth checking this area again. I sometimes had a smell of petrol but eventually found that it was an almost invisible crack on the rubber seal of an aftermarket cap. Replaced just the seal over a year ago and never had the problem again.

 

[garrymon]

Hi Mike Thanks for your reply. There is no smell from outside the car when the engine is running, although because the problem is intermittent and I'm inside the car when it happens, it is difficult to tell if there is an external smell. I've owned the car since new, so I know that there have been no spillages inside the car. Regards Garry

 

[garrymon]

Thanks Richard I don't know but I'll check that area the next time I notice the smell. Regards Garry

 

[garrymon]

Hi Steve No sign of cracking on the new fuel cap. Regards Garry

 

[boba fett]

ORIGINAL: Richard Hamilton Welcome Garry! Jaz are well respected as Mike says, and I doubt a main dealer would have done better for this type of problem. It sounds to me like it might be a problem with the carbon canister (evaporative system) which is located in the front wing, near the filler neck. Is the smell coming from that area?

It's this for sure, shut off all the heater blower vents and the smell will pretty much go away. The canister splits Can't believe this has not been diagnosed by the specialist!!!!

 

[JuliusF]

Sounds like a very similar problem that has been dumbfounding my indy (and others) for the last 18 months - its under investigation at the moment, but its an easy one to miss. Has your O2 sensor been throwing errors at all? That's part of the clue set I think. You might also notice a repetitive rising/falling breather tone on idle (and it sort of sounds like a jet spin down when you turn the engine off), plus the idle occasionally hunting/dipping when warm - also part of the symptoms - I hadn't realized significance being a first time owner. Hopefully on the road to recovery! Regards. J

 

[JuliusF]

Don't know if you got it resolved, but mine has been - finally - it turned out it was the vent valve at the engine end, not at the tank (carbon cylinder end) - the valve was not operating correctly, seems it was sticking open when the engine got warm - hence hot start and rough idle issues, as well as petrol smell - finally fixed, hallelujah!