$sliderIndicator.on('click', 'li', updateMainSlider);
autoRun()
// add a variable to store interval identifier
var interval;
function autoRun() {
    var mainSliderChildLenght = $sliderchildren.length;
    var i = 0;
    var next = true;
    var dir;
    // save interval identifier
    interval = setInterval(function () {
        // your code - unchanged
    }, 5000);
}
function updateMainSlider(a) {
    var visibleSlide = $sliderchildren.filter('.visible')
        , actualTranslate = getTranslateValue($sliderMain, 'X');
    if (a == 'next' || a == 'prev') {
        // your code - unchanged
    } else {
        // clear interval
        clearInterval(interval);
        // your code - unchanged
        // now add this to restart the interval
        autoRun();
    }
}