116 John Deere fuel pump

I replaced the engine on my 116 lawn tractor with a good one from another 116. This has been a 3-year project. Now I have got it running but just on either or by squirting gas in the carb. I am not getting any fuel to the carb. I know about the fuel system problems these had-I believe this has the "pulse" system now. I am not sure if I have it hooked up right. I tried the search the archives but it doesn't work for me. Any body have an idea what I should do?

I am thinking there are different Deere mowers with similar model numbers and I don't know which you have:

Is this the about 20 year old 116 with the vertical shaft Briggs opposed twin cylinder engine on it?

Or is it the even older one like a 110 or 112 with the cast iron horizontal shaft Kohler engine on it?

Product of 1983. My uncle bought it new, I'd like to keep it going. It has mowed thousands of acres. This is a big lawn. Engine froze up a few years ago, found a cheap one with a good engine. Son decided to replace engine a few years ago, so He tore it apart and lost interest. I have now put it back together. I think the donor mower had an electric pump and mine has the pulse pump. I don't understand how a pulse pump works. I think I got it plumbed right. It has the briggs vertical shaft twin.

O.K.: 16 hp vertical shaft Briggs.

That engine has the pulse pump built onto the side of the carburetor. If its not getting gas, probably you need to get a carburetor kit and clean the carburetor as well as replace the diaphragms in the pump. Be careful taking it apart, there are some tiny hair-like springs about 1/4" long that close the pump flappers.
In cleaning the carburetor itself there is either a solenoid or a plug low on the side of the carburetor. Behind that plug or solenoid there is the main jet. You need to clean that jet, that is usually where the running problems are.

The way a pulse pump works is when the pistons go up and down in their cylinders it changes the volume (and pressure) of any air in the crankcase. 2 cylinder engines have twice as many changes but I am thinking 1/2 the net change in pressure.

The pressure goes down when the piston goes up the cylinder and goes up when the piston goes down. The pulse pump uses those changes in pressure on one side of a diaphragm to alternately cause a vacum and then a pressure on the opposite side of the diaphragm. Then check valves (flaps on a rubber sheet) are used to pull fuel from the tank when there is a vacum caused by the diaphragm and then push the fuel toward the carburetor when there is a pressure caused by the diaphragm.