Fuel vapor canister and bad gas

[Bukowski]

If the gas goes bad in the tank, say for a long long time, how does that affect the fuel vapor canister adsorbant? asking for a friend.

[DannoXYZ]

Gas doesn't really "go bad" like milk which decays and rots. Hydrocarbons, especially aromatics, are extremely stable (it was in the ground for millions of years before being put into our cars.

What happened with old carb systems was that the gas-tank and carbs were vented to atmosphere. This allowed the lighter fractional elements to evaporate leaving behind the heavier stuff. In low-volume areas like thin fuel lines and carbs, this fractional distillation occurs quicker and all the liquid may actually evaporate completely and leave a rubbery plastic-like film that'll clog the carburetor jets.

This is not a problem with modern sealed systems. Some examples:

- in 2001 I had a 951 that sat for a year waiting for engine-builder to deliver engine for Open Track Challenge. Got the engine week before event and I stayed up 72-hours straight putting in the engine. Started on 1st crank and ran without any issues.

- 2014 I non-op a 944na that I was going to use for spare parts and eventually dump. While I was replacing clutch in 951 last weekend, a friend needed ride back from airport at 2am. Hmmm, I threw 951's battery into 944 and wrroom, it started right up. Got to airport and had to wait an hour because flight was delayed from LAX.

Modern fuel systems are sealed so that there's no evaporation. You don't have to worry about fuel drying out in the cars like the old days and turning into varnish. The EVAP canister works on vacuum with a valve. Without intake-manifold vacuum to suck it out, the gas won't be vented to the intake, so it'll be stored just like in the tank.

The key here is that the gas is in a sealed system with no vents to atmosphere. There won't be any drying or gumming up.