The autovac is an early mechanical fuel system component mounted high on the firewall. It uses intake manifold vacuum to pull fuel from a low-mounted rear gas tank into a small internal reservoir. From there, the fuel feeds downward via gravity into the carburetor. It was widely used on older vehicles before reliable mechanical or electric fuel pumps were developed.
The engine keeps starving for gas on long hills because the autovac has a cracked vacuum line.
When diagnosing fuel starvation on vintage cars with this system, check the float valve inside the chamber, as it frequently sticks and breaks the vacuum seal.
Also heard as
- vacuum tank
Related terms
Induction
The process of drawing air or an air-fuel mixture into an engine's cylinders.
Intake manifold
The engine component that distributes incoming air or air-fuel mixture evenly to each cylinder.
Classic car
An older vehicle maintained for its historical interest or aesthetic appeal rather than daily transportation.