Fuel/exhaust smell in cockpit.

[kfosburg]

(1971 911 with webers)

After converting from the factory air cleaner to k&n with rainshields, I always have a gas smell while driving. I don't really notice it so much until I stop and smell my shirt. Then, it is noticable like gas and gas/exhaust. Engine is not tuned perfectly, but isn't too far off - maybe a bit rich.

How should I be terminating the hoses that come from the charcoal canister and oil breather?

Could I have an exhaust leak?

Thanks in advance,

Karl (aka stinky)

[copper]

Have you changed shirts?

Just kidding.

I have a 69 911T.

Same problem.

Various areas that could be causing the problem. Have narrowed this down through my own investigation.

Most likely cause is fumes entering the cabin through the heat vents.

Places to check,

Check heat exchangers for holes.
Check exhaust connections for worn gaskets/loose joints.
Check heater hoses from engine to heat exchanger for holes.
Check heater control boxes. If original, they are most likely rusted and not sealing when closed.

If your car is a summer driver only, you may want to consider closing them off at the cabin entrance side.

Any leak in the exhaust system anywhere near an intake point (intended or not) between the engine and the cabin inlet will let fumes enter.

My car is also a little rich, which adds to the odour. I am working on fixing my problems.

Jim

['76 911S 3.0]

I have also noticed this in my '76. Only happens when I take hard right hand corners. Think it's from the filler hose spilling over and leaking some gas out the breather hose. Strong smell of gas inside the car. Just a thought.

[RoninLB]

many Heat Exchangers leak and the driver never notices it till it's extreme.

Sometimes an old gas cap gasket will leak briefly on sharp turns. there are various size gaskets for our various caps.

[rpiper]

I replaced the gas cap and the smell disappeared.

[yeuporsch]

Mine is a 72 with weber and K&N filter. Did the same thing. The exhaust was getting under the car when at a stop and got suck in through the fan and going through the heat exhanger and into the cabin. I have a stuck flapper box. I remedied it by welding extension to the exhaust pipe to make sure gas exhaust is vented completely away from the engine area. The gas smell still persists and is probably due to the water shield setup. Next job is to fix that flapper box.

Hope this help.

John

[copper]

Check your fuel sender gasket also.

Depending on when it was last changed, it could be leaking a little. They are made of cork, so they don't last too long.

Fuel sender is in the trunk. Lift the carpet and you'll see it on top of the tank. You'll see the fuel gauge wires going to the top.

The sender is a round unit with six screws around it's top. Should be VDO. Pressure in the tank can cause vapours to leak out around the sender if it is either loose or the gasket is worn.

I just replaced mine. Cost $2.45 on ebay, $2.49 for shipping. Genuine part.

Next time you fuel, raise the trunk lid and push the carpet aside. Watch the lower edge of the sender where it meets the tank, where the black undercoating is. (worn undercoating here is a good indicator of a bad seal on the sender). If there is a problem with the seal on the unit, you will see air escaping from around the lower edge as it reaches the top of the fuel tank, or worst case, as mine did, fuel will come out around the sender.

As this is directly in front of the cabin, and the fresh air intakes, this can account for a fresh fuel odour.

Can you tell if the odour is more fresh fuel or exhaust odour?

The sender gasket replacement took about 5 minutes. If you need to do this, drop me a line and I'll give you some pointers.

Jim

[RoninLB]

Originally posted by copper
Check your fuel sender gasket also.

Depending on when it was last changed, it could be leaking a little. They are made of cork, so they don't last too long.

there is an upgrade rubber gasket

[kfosburg]

Thanks for all the great suggestions.

The fuel tank is new and there is a new sender gasket which is not leaking. There is no gas smell in the trunk and it is more of an un-burnt fuel/exhaust smell than pure raw gasoline.

I will change out the gas cap since mine is 33 years old now, but I don't think that is the root cause.

I think that John's idea and experience is what I'm experiencing. Where is this flapper valve? What did you do with the three hoses that used to be connected to the air cleaner housing? How long of an exhause extension did you install?

Thanks,

Karl

[copper]

Karl

Look under the car. on the front side of the heat exhangers, (opposite the muffler side) you'll see the pipes lead to round boxes with triangular or pie shaped holes in them. These are your heater control boxes or flappers. Should terminate near the wheel wells.

Check their condition. Check the seal when your heat lever (in the cabin) is completely down.

These, as I said in a previous post are probably the cause of the problem, allowing fumes to enter the cabin.

Jim

[yeuporsch]

I welded about a 5 in extension pipe to each of the exhaust pipes; I have the dual out exhausts that comes out right under the engine fan. So far, no exhaust fume in the cabin at idle. Before, I would come into the office and smell of exhaust fume on my clothes after driving the car. Also, I discover that my car is still running a little rich, which would explain the gas smell from the exhaust before.

John