Usage of AWK command

I have a file in tabular format called emp.txt which has all details for employees.

eno   ename   esal   ecity
1000   a      2000   Pune
2000   b      4000   Nagpur
3000   c      6000   Delhi
5000   d      1000   Hyderabad

Now I am trying to extract information using awk command for employee where esal is 6000.

Wrote the below expression but not getting desired output, any suggestions ?

awk '{if($3="6000") print $0}' emp.txt

Output I got,

eno ename 6000 ecity
1000 a 6000 Pune
2000 b 6000 Nagpur
3000 c 6000 Delhi
5000 d 6000 Hyderabad

Expected output

3000   c      6000   Delhi

Thanks,
Piyush