Hello aspirant,

It is entirely depends on your time shedule.
While giving time for upsc preparation, you should not ignore the study of ECE.And as we know graduation is compulsory for UPSC exam.So please focus on graduation first.
But if you want to know, how to balance engineering study as well as upsc preparation, then I'm mentioning some points here.
1.First of all you have to understand total syllabus of the exam.after that,
2.You have to make a timetable ,
And then utilize your time accordingly.
3.Read newspaper daily or Read news on television.This habit will be useful further.
4.Prepare self notes and read that notes
5.Focus on clearing concepts or doubts.
6.Refer last 10 years question papers,so that you will get an idea about the UPSC civil services examination.
7.you can start reading from basic books which are necessary to read...and then you can read many of the reference books.
And see If you are preparing for upsc then most importantly you will be very beneficial, if you do time management from now on.
And(we can say that until your graduation is complete) how effectively you study in the time is important than how much time you spend studying for this exam.so think on that.

All the best
And give your best shot...

Hope this answer will help you