Carburetor Work

How does the carb work?

Basically a Carburetor is a pump used to inject fuel into the engine, as gasoline leaves the fuel tank it gets pressurized by the fuel pump, the pressure is produced through a venturi where the pipe narrows down then widens out again, which pushed the fuel to speed up in that area. In a carburetor there is a series of springs and ball bearings to measure the amount of fuel that flows into the engine, this depends on the engines speed (RPM) or load put on the engine. where the fuel comes out the other end of the venturi, it flows into a chamber where it is mixed with air from the air intake.

Components of a carburetor?

The main components in most carbureted systems are a float chamber, a venturi, the throttle, idle circuit, main circuit, a choke and an accelerator pump.

1.  Float Chamber: 
2. The float chamber holds a small amount of fuel at atmospheric pressure ready for use. It is refilled by a float driven valve when the level drops the float drops too and opens a valve which allows more fuel to be delivered into the float chamber. The float rises with the replenished fuel level, this shuts off the valve and stops the flow

1. Diaphragm chamber:   
2. A float chamber can some times not be suitbale for certain engines, for example in chainsaws and leaf blower which are turned upside down numerous times a float chamber will not preform as it should and will be faulty. The diaphragm chamber uses atmospheric pressure to push the diaphragm in and out which pumps the fuel, a needle attached to the diaphragm feeds the fuel as the seal moves inwards.

What is the purpose of the float in the carb?

the float is set in a float chamber when the fuel rests before being pumped into the engine, this is in place to provide a steady flow of fuel when it is needed and keeps the fuel at the atmospheric temperature. when fuel is extracted from the chamber the float drops, which opens the inlet valve and lets fuel flow in. In the other way, when the float rises it cuts off the valve and stops the flow.

What is the purpose and how does  mechanical lift pump work?

A lift pump functions to raise the level of fuel or other liquid up through a given system. In automobiles, the fuel lift pump works to build pressure or suction in the gas tank, thereby encouraging the fuel level to rise to the injection systems and on to the engine block. Lift pumps have several applications beyond automobiles and are also used in sewage systems to pump out waste from a full sump pump.

What pressures would you get from this time of pump? 
Not to sure will have to ask

http://www.google.co.nz/imgres
http://www.cdxetextbook.com/fuelSys/gasoline/operation/carburetorcomp.html
catalogs.indiamart.com › Automobile
http://faq.ninja250.org/wiki/How_a_carburetor_works:_Carbs_explained 
http://www.thedieselstop.com/forums/f30/does-sound-like-bad-mechanical-lift-pump-189818/