notaguru

'83 US spec.
On many cars, the fuel tank is depressurized by a pump or engine vacuum to prevent evaporating gas from reaching the atmosphere. On such cars, internal pressure is always below ambient pressure unless the filler cap is loose or there's a leak, in which case the system detects the excess pressure and triggers an alert.

Do our cars do that?

Thanks.

FredR

The fuel tank has to be vented in some circumstances and have a vacuum breaker capability for when the tank level drops. The later models [S4+] have such a system but as I am aware there are no alarms. I have no knowledge of how your model year is kitted out but I fully expect it has similar capability

ammonman

The '83 US cars use a charcoal canister system. The fuel tank is connected to the canister through an expansion tank (in the passenger side rear wheel arch.) The fuel tank is open to atmosphere at all times via the expansion tank, charcoal canister and canister vent line that is open to atmosphere. The vent pipe ends behind the rear bumper cover. As fuel vapors build up in the tank the pressure is relieved to atmosphere through the charcoal canister, which absorbs the fuel vapors. As vapor pressure in the tank drops (overnight temperature drop for example) atmospheric pressure pushes air into the fuel tank thought the vent line and canister. When the engine is fully warmed and running above idle a series of valves opens a connection from the charcoal canister to the intake manifold. Since the intake manifold pressure at part throttle is below atmospheric by quite a bit, air is drawn through the charcoal canister vent line. The collected fuel vapors are pulled from the charcoal by the airflow into the intake manifold and burned with the fuel/air mix. As Fred says, there is no pressure sensing in these systems as there is in a modern sealed tank/vapor system.

Mike

Ducman82

^^ well said. yup, no "smart" sensor for that system