Fuel smell

[8adgerx]

I have a 81sc with Webber carbs and k&N filters I also have a rain shield fitted under the deck lid grill.

The problem I have is a very strong fuel smell in cabin when the heating is on.

I think it’s running a bit rich but could the rain shield be adding to the problem.

[fizeus]

Fuel smell is generally due to not working canister system ... if you only have it in the cabin when the heat is on it could be a leak in heater exchangers but it should be burned fuel smell (rich or lean is influent) and it's very dangerous.

[8adgerx]

Originally Posted by fizeus

Fuel smell is generally due to not working canister system ... if you only have it in the cabin when the heat is on it could be a leak in heater exchangers but it should be burned fuel smell (rich or lean is influent) and it's very dangerous.

I don’t have a fuel canister in engine bay as it was removed with the carb install the ssi’s are new my thought was maybe the rain shield was allowing enough vacuum on the fan to draw fumes through the air filters and into the heat exchangers that way.

[8adgerx]

Could the rain tray be causing a vacuum across the filters ??
No canisters as they where removed with the carb install.

[MrBonus]

You might check in and around your fuel tank. I had the same problem twice and the first time, my fuel pump was leaking and the second time, the fuel sending unit gasket was leaking.

[8adgerx]

Originally Posted by MrBonus

You might check in and around your fuel tank. I had the same problem twice and the first time, my fuel pump was leaking and the second time, the fuel sending unit gasket was leaking.

The smell is coming through only when the heater flaps are opened making me think it being drawn in by the fan.

[8adgerx]

I don’t have any smell when the heater flaps are closed

[RobFrost]

You could have a fine leak in the fuel system in the bulkhead area, and the heat is evaporating the fuel and circulating within the cabin.

Also, for fear of suggesting the obvious, try taking the rain cover off to test whether it's that.

I'd want to know for sure the fuel tank expansion system etc. is disconnected.

Do you have any heat insulation between carbs and cylinder heads? Another member had heat from the engine boiling the fuel in float chambers. This would cause fuel fumes in the engine bay and I could imagine it causing your experience. Is there a strong smell of fuel in the engine bay when the engine's hot?

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[Tea Tray]

Did you recently add the rain shield?
I agree w/ RobFrost ^^ suggesting removing the shield to test.
Any appreciable restriction the shield adds to air flow can cause/exacerbate your issue.
Could the rain shield be spaced further away from the grill to reduce restriction?

[8adgerx]

Some excellent thoughts the car is off the road but I have removed the shield.
The fuel boiling in bowls is a good point and that would be a great check to see if the smell increases withe engine temp.
I’m pretty sure there is no fuel leaks front or rear.
👍👍👍

[BoxsterGT]

You really need to tell us more about the fuel system.

Fuel won't boil until the motor is HOT, not just warm.

When do you get the smell? Immediately after starting & driving, or is it only after being fully warmed up?

What do you have for fuel lines and Fuel Pressure Regulator? Is it a PMO?

What do you have for a fuel Pump? If original SC with a PMO, the fuel pressures are still High through the system until after the PMO regulator.

How old is the system? I expect you have hose clamps with all of the Carb conversion hoses.

Hose clamps are not adequate for high pressures, especially when a few years old. Perfectly fine for the low pressure side.

Len

[BoxsterGT]

When nothing is obvious, the word "permeation" comes to mind.

Everywhere there is high fuel pressure this can occur, as with most of your system, even though you have Webers.

This happens even with the "Braided SS Hoses" that comes out of China. And with the SS cover you cannot inspect the hose over its length.

Len

[RobFrost]

Another thought here, is there ethanol in your fuel, possibly degrading hoses?

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