I tested it on my end by passing context (this) to $sel.change, it works fine. you can call both saveEditCell and quitEditMode in $sel.change
Which version of jQuery/ jQueryUI are you using. I can test that in it as well.
Are you losing the current value of context somewhere in the call stack of functions. There is an alternative way of calling pqGrid API which may be helpful to you.
$sel.change(function(evt){
//this points to select list in change event.
$(this).closest(".pq-grid").pqGrid("saveEditCell");
});