no brake pressure

im in the middle of getting my fathers xj750 seca fixed up so he can ride again and im about done but i have run into an issue with the front brakes. with fluid in the master cylinder resevoir when i pump the brakes it does not suck any fluid out of the resevoir and into the lines. i can however take the solid brake line off of the splitter (the piece under the fog light that send the fluid to each caliper) i can pull in the lever then plug it with my finger and release the lever and it will suck fluid, if i do it again it will have enough in the line to squirt out when i pull the lever. then i reconnected it and tried pulling the lever and it wont suck anymore fluid. i tried rebuilding the mc and that didnt solve it, i made sure all my lines are clear and not collapsed. im completely lost, any help would be greatly apreciated

 

Did you replace the brake lines recently?

 

try checking your master cylinder. should be 2 holes in the reservoir. clean it up. i know i had this issue and then i noticed a hole was plugged in my master cylinder then i got that clear and sucked the fluid through with a syringe and tube and after that it was a breeze. just be sure to keep the master cylinder full.