A small diaphram about 3/4" in diameter. In order to change the pump you may have to pull the top off the carb. The diaphram normally has a small "tit" of rubber that pull the new diaphram into place with. I normally wet the diaphram with some gas to ease installation of the diaphram. If you break off the tit, you'll have to buy a new diaphram and start over.
When I started to loosen the screws that hold the cover on fuel started coming out. Is it supposed to have fuel in that area? Is the orange part inside the carb part of the accelerator pump to? I didnt want to mess with something I didn't know about.
Sometimes it squirts out fuel good, then sometimes it won't squirt fuel at all. The reason why I was asking for help again is because I didnt know if the orange part was part of the assembly, I never had a Ford 2 barrel carb apart. All fuel line is new, filter is new, tank is new, removed mechanical and installed electric fuel pump. Runs good for a while then it will start to miss and if I push the throttle it will die if I let back off it will continue to run but miss. Moved the throttle by hand under the hood several times never squirted out fuel. Turn the engine off a few minutes then crank it back up and turn it back off then move the throttle by hand again and this time it squirted out fuel. I have had the accelerator pump go out on a 78 Bronco I use to have put I had a friend replace it. The carb I have on my 79 is a reman carb that is only about a year old.
I just replaced mine on my 82 bronco i just bought (mine was completely froze in place had to hammer it out of the casing) it is not hard to do just remove the four screws as everyone above mentioned. and yes fuel will run ot of there. there is a spring inside as well make sure that doesn't fly out, replace the spring and diaphram and bolt it back on.....took me about 15 minutes to do not a complicated process.
Took the diaphram out today and it looked fine. Turned on the fuel pump then pumped the carb, fuel squirted out good. So I guess I have trash in the carb around the needle and seat. Runs good for awhile then idles really low and misses will die if I give it gas because it is just getting air, if I close the choke it will smooth out some. As i mentioned above carb is not very old, I guess it needs to be took apart for a good cleaning, something got inside and clogged it up.