OK- you need to become familiar with the basics of carburetor operation. I'm not being rude, just noting that many people these days don't know how to properly live with a carbureted vehicle.
(1) Fuel pump operation. Old mechanicla fuel pumps operate off a lobe on the camshaft or an eccentric that bolts to the front of the cam. Mechanical fuel pumps typicaly make 5-7 PSI or so, which works out great beacuse most carbs only need 4-5 PSI of fuel pressure to operate. The fuel supply PSI needs to be that low because the carburetor float actually functions as an on/off valve controlling the fuel flow. When the carburetor float bowl (discussed below) gets full of fuel, the float lifts up and presses the inlet needle into the inlet seat and stops the flow of gasoline into the float bowl. Too much fuel pressure and the fuel pump will overpower the float and cause fuel to overfill the carburetor float bowl leaking to a massive fuel leak into and onto the engine.
(2) Carburetor construction. The main point here is the float bowl. The float bowl acts as a small reservoir/holding tank of fuel for the carburetor to feed the engine. Contained in the float bowl are the float (the on/off switch for fuel flow), the accelerator pump, and the main jets and main metering rods (if so equipped). This is an oversimplification since there are many designs of carburetors with different fuel metering arrangements, but for the purposes of this discusion that is enough detail. The fuel in the float bowl serves an number of functions. It provides a ready supply of extra gas to be squirted into the carburetor throat when you step on the gas and operate the accelerator pump. It also stores a small amount of fuel on which the engine will run when first started and the fuel pump has not drawn fuel from the tank yet.
(3) Gasoline evaporates. All non-marine application carburetors all have vents to the atmosphere for a variety of reasons (none of which are important here). These are typicaly called the "bowl vents." If the vehicle sits for more than several days, chances are the fuel in the float bowl will either completely or partially evaporate out the bowl vents. In the bad old days, we all just lived with it. Garages and car interiors often smelled like gas because the cup or so of gasoline left in the carburetor evaporated and the fumes got everywhere, including into the "fresh air" intake for the passenger compartment. Beginning in the late 60s, car manufacturers began experimenting with ways to trap the evaporating gas and make it able to be reused. Early methods included trapping it inside the air cleaner, but the generally accepted industry standard became the charcoal cannister.
Charcoal canisters work by collecting the gasoline vapors that escape from the carburetor (and fuel tank on later models) and storing them in a charcoal matrix to be reintroduced into the carburetor when the engine starts back up. This reduced pollution, make starting easier, eliminated the nasty gasoline smell from garages and interiors, and saved money since you were no longer buying gasoline and just letting it evaporate. The charcoal canister usually has one to five hoses on it. Early models just had a hose that went to the bowl vent on the carb. Later models had two hoses that went to the bowl vent(s) and another port on the carb as well as a hose that went to the vent on the fuel tank. The most advanced designs had numerous hoses that went to many different places. All these hoses were the drawback to charcoal canisters. Many auto enthusiasts and "mechanics" who did not understand what all the hoses were for, were intimidated by all the hoses, thought all the hoses were messy, or just thought auto emissions didn't matter, disconnect the systems or removed them or levelled baseless criticisms against them. The truth is charcoal cannisters help your car run cleaner, be more efficient, and have absolutely zero negative impact on performance.
(4) Proper carburetor operation. "FURIOUSLY pump the gas pedal a gazillion times as quickly as possible while its trying to start" is not the correct way to start a carbureted engine, especially one that has been sitting. Doing this can actually cause the internal parts to wear out prematurely. Here is how a properly functioning carburetor on a daily driver street driven vehicle should operate. If the vehicle is cold, you should be able to depress the accelerator to the floor once, release it, turn the key, and have the car start. Some models require the one pump followed by holding the accelerator pedal 1/3-1/4 of the way dwn while turning the key. In some circumstances (very cold areas) you may need to pump it twice or even three times, but most places only need one pump. The engine should start easily and go immediately to a high idle that drops within a minute or two (longer in cold climates).
When you pump the gas that first time, several things are happening. Externally, the choke valve should be closing fully and the fast idle linkage should be getting set to hold the thottle partially open. Internally, the accelerator pump operates and squirts gasoline into the intake to richen the mix and make starting the engine easier.
(5) What happens when the float bowl is dry. When the float bowl is empty, on the first pump of the accelerator pedal the choke will be set but the accelerator pump will have no fuel to pump into the engine. Depending on the type of carburetor you have installed, the acceleretor pump plunger may be of a design that has a rubber (actually, not rubber but some fancy synthetic material. A long time ago they were leather, but those days are long gone) cup that goes up and down in a small cylinder in the float bowl that pumps the gas into the carb throat. When the float bowl is dry, that little rubber cup scrapes along the edges of its cylinder and wears itself down every time you pump. This is why pumping the pedal many times while you wait for the float bowl to fill can damage the internals of the carb.
(6) The right way to start a carburetor if the float bowl is empty. If you know the float bowl is empty, the best way to start the engine is to remove the air cleaner and fill the float bowl with gasoline or carburetor cleaner through the bowl vent tube. If that isn't an option, pump the gas ONCE to set the choke and fast idle, then crank the engine for a while to give the mechanical fuel pump a chance to pump some gas up into the float bowl. This can often take 30-45 seconds of cranking. After the first 15-20 second of cranking, pump the gas pedal once. If the engine doesn't catch and run, keep cranking and pump once every 5-10 seconds untli the engine catches and runs. Never crank for longer than about a minute. You will wear out the starter motor and the battery. If the engine doesn't start after cranking for a minute, let it sit for about 30 seconds and try again.
(7) Installing an electric fuel pump. Installing an electric fuel pump is not difficult and might actually be a good idea for you. With an electric fuel pump you can prime the carb with gas before ever touching the accelerator pedal. Here are Holley's instructions on how to install one of their aftermarket electric fuel pumps intended to work with a carb. I strongly STRONGLY recommend you follow those instructions and install a safety shutoff.
http://www.jegs.com/InstallationInstructions/500/510/510-12-801-1.pdf Hopefully this helps de-mystify the carburetor and helps you solve your problem. I strongly recommend you get a factory service manual for your van and read it to learn how everything works. That will help you operate it better and keep it around longer.