Check that the length of the push rod is correct. It's about the only thing taht could cause your problem. Except, of course if you have connected the inlet and outlet around the wrong way.
HTH.
unbolt it and pump her by hand using a screw driver or similiar, if this works then lay under the car while someone else turns the fan apply pressure to the rod and make sure it moves up and down. If it does then measure it, subtract and standoff the pump may have and you can work out how far it is pushing the pump. I have had pumps that only worked in the top 1/4 before.
There is at least 2 diferent shaft lengths for the type 1 maybe there is for teh type 4 as well.
or perhaps a new but faulty pump.
NOS... new old stock , wonder how long it takes for the diaphram to rot. Lets hope there is another reason.
Regards,Glenn>
Simon, if it's stroking, apart from a ripped or damaged diaphragm, it can only be the valves. It could be the inlet valve being stuck in its seat. When the diaphragm goes down, it creates a vacuum which should over-ride the fine spring holding it in place & allow fuel in. If the pump has been sitting on the shelf for decades, the valves could "oxidise" & stick.
it happens dude!:P
cheers
rhys:bounce
A good result, and some one that is big enough to admit falibility.🙂
Regards,Glenn>