I have a sump in my basement that collects discharge water from my washer, furnace, and water softner. The sump pumps the water straight up to the ceiling, where it ties into septic system. All the water drains to my septic tank/field outside.

The kitchen sink upstairs gurlges every time the sump runs. There is a check valve about 5 feet above the sump, and the kitchen sink has a Studor valve on it. I replaced the Studor Valve, but it didn't help.

I never smell any gas, so I'm guessing it's sucking air, but that should be solved by the Studor valve.

Any ideas?

The Studor valve is a mechanical replacement for a vent. It can go bad. Not venting won't cause an odor but if it sticks open instead of closed you will smell sewer gas.