Short guide to vacuum systems
(1) Pump for a while. Water vapor pressure at your current ambient temperature of 23 °C is 21.1 mm Hg, but the temperature and therefore the v.p. may be higher when you have everything in the sun. Just a little moisture somewhere (and it's everywhere) can keep your pump working for hours or days.
(2) Leak test. At your pressure regime, you can spray ethanol at the joints. A leak will suck in ethanol, the liquid will evaporate and give you a jump to a higher pressure. Later, the leak may freeze shut with ethanol (pumping a liquid cools them down), so the pressure may improve for a while. Best have one person do the spraying and another watch the vacuum gauge.
(3) Use vacuum connectors instead of pressure connectors. The quick-connects you use look to me like connectors for pressurized air. The seals are different, so the wrong kind may or may not seal.
Good luck!
