Gas Fumes in the Cockpit

[ChrisInNashville]

For nearly a decade, I have struggled with gas fumes in the cockpit but only when the gas tank is over 1/2 full.   This predated my full restoration that included an engine rebuild by Metric….and the problem as continued

Last year, I replaced the charcoal canister and related hoses.  In addition, I checked the vent line to be sure it was clear.  For the most part, I use ethanol free gas.  At first, I thought I’d fixed the problem because the old hoses were so deteriorated…but alas, as of yesterday, after filling the tank slightly over 1/2 full, I’m still smelling the fumes.

What am I missing?   Why do I only experience this only when the tank is over 1/2 full?

Thoughts?

[Pawel66]

I am sure others will provide a better advise, but mine is a simple one, good so start with.

Open the inspection window cover in the trunk floor and check for gasoline leaks in the fuel sender area.

By the way: if you are talking about the small expansion tank in the rear right part of the trunk - no charcoal there, just an empty tin with a couple of dividers inside.

[Pinder]

If Sender unit is sealed and no gas present there. Take the cover off where the neck of the Gas tank filler pipe is. there should be vent lines there and check the connection is good, use hose clamps not twisted wire.

[Cees Klumper]

One perhaps unlikely but still obvious suspect is the tank itself. I repaired my Lancia Fulvia tank that had a pinhole leak at the top. If your tank has similar, maybe a teeny-tiny leak at the seam for example (which is about halfway up I believe) then you will smell gas seeping out and evaporating out of that opening. Worthwhile checking?

[ChrisInNashville]

Thank you…I’ve checked the technical manual to familiarize myself with the sender unit.  I also see the need to disconnect the battery to prevent sparks.   How dangerous is checking this unit?

[Benz Dr.]

Thank you…I’ve checked the technical manual to familiarize myself with the sender unit.  I also see the need to disconnect the battery to prevent sparks.   How dangerous is checking this unit?

Not very dangerous at all. Very low voltage going to the sending unit. Turn off your ignition switch which cuts off all voltage. But go ahead and disconnect your battery.

Don't go anywhere near your trunk with a trouble light and your sending unit removed from your fuel tank. THAT can be VERY DANGEROUS!!!! Loose bulb on your trouble light can cause a spark which will ignite the gasoline fumes and your car will be burnt toast - maybe you as well. We sure wouldn't be happy hearing about that........

[Harry]

I also have gas fumes in the cockpit but only at startup.  I don't see any indication of fuel leaks under the hood..  I've meant to also check the cold start valve on the intake although the car runs very nicely.

[mmizesko]

Chris,

I know you've posted plenty, as I tried to figure out the model and year of your car.  Now I know it's a 280SL.

You must have looked into the vapor expansion tank and it's associated connections.  Those little nipples on the bottom right crack and leak fumes, mostly when you have a full tank, but sometimes when they feel like it.  I've attached a pic.  isn't this tank mounted on the drivers side of your trunk?  the hoses might be the culprit too?  This was the source of my "fumey cockpit".

You've probably already investigated this.

Mike