What does "Do not pump it" refer to in "Place the accelator pedal all the way to the floor, and hold it there. Do not pump it"? To pump the accelerator? If so, what's the purpose? Thank you.
"Do not pump it" means, keep the accelerator pedal pushed firmly to the floor while attempting a "clear flood mode" operation when starting the car.
It used to be, with carbureted engines, you'd "pump" the accelerator pedal in order to get fuel into the engine, which would make it (sometimes) easier to start. Watch any old movie (from the 1960's or 70's) where they are starting a car and you'll see them stabbing the accelerator pedal over and over again with their foot, working the carburetor's accelerator pump in an attempt to get some fuel to go into the engine.
To some hold overs from that era, people still try to "pump" the accelerator pedal while trying to get their car started. In a car with a fuel injected engine, you shouldn't touch the pedal in a car during startup, unless you believe there is a "flood" type situation. When an engine is "flooded", there is an extreme rich condition in the engine which won't allow the engine to start. At some point, with excess amounts of fuel, it will not ignite. This is the point at which an engine is considered "flooded". With most fuel injected vehicles, the way you clear this out is to push the accelerator pedal to the floor and hold it there, without pumping it, then turn the key over in the ignition to attempt to start the car. As long as your foot is on the accelerator and it's all the way to the floor, the computer keeps the system in "clear flood mode", which will not allow the fuel injectors to release fuel into the engine. At the same time, the throttle body is wide open, so the engine can ingest as much air as it can. These two things together allow for the rich condition to be purged and the engine should be able to get started sooner because of it.
You have a carburetor with an integrated choke. When the engine is cold the choke is activated by a single full depression of the accelerator pedal.
(Aussies - VK Commodore, not many around, I wonder why?).
You then start the car and the choke will abate as the car warms up.
Carburetors also include fuel pumps, the purpose of which is to overcome the sudden loss of vacuum (or venturi airflow) and keep the mixture rich enough or even slightly excessively rich.
Pumping the pedal whilst the engine has not yes been started may flood the engine, shorten the life of your oil, and contribute to upper cylinder wear, as well as making the engine hard to start, which will stress and possibly exhaust your battery.