Thanks 2721955Meteor , I re re-checked my lines , they`re on  the correct way , manifold line to the outside , wiper line nearest the block.
I am beginning to think the vacuum side of the pump is failing somewhere. Old `56 Mercury Shop Manual says to pull the lines off at the
rubber connections on top of the pump , and check pressure there ...no less than 10"Hg. I will have another look today.
Regards,
John.

do you have the lines to fuel pump on backwerds.the pump should suplement the engine when engine vacume drops. if the pump does not help ,just get a small propane cyl and convert to a extra vacume source with a check.i am not a fan of the dual dyaphram fuel pumps,but if it is hooked up in corectley it is a neg help. henrey should have  had a kick re the vacume wippers, especialey with a standerd trans.

Hello All , I have a `56 Mainline , trying to get wipers working correctly . Wipers can barely lift themselves from the park position on the screen
when I have them hooked up to the DA fuel pump . When I connect the wiper motor directly to the front  manifold port , they work fine,
even when I rev the engine . Vacuum reading off the hose to the vacuum wipers is roughly 20 Hg inside the car . DA pump is supposed to be rebuilt,
is it possible for DA pump to read 20 Hg , but not able to operate the wiper motor ?
Any input would be much appreciated , I must be hooking something up wrong .
Regards,
John.