Same thing for any "hand operated" vacuum pump. they're all shit.

I bought a "name brand" pump from Amazon to bleed the brakes on my boat trailer and it couldn't pull any vacuum. Returned it.

Realized I was being a dumb ass because I already had a small fluid extraction pump I use to pull the oil from my boat engines that produces some serious vacuum. Worked a charm with one little piece of rubber fuel line hose to adapt to the line insert.

Only issue now is I probably should clean the tiny amount of brake fluid from it before using again.