Question: Why won't my lemon filling in lemon meringue pie set up, it's runny.
By: Charlie
Published: January 4, 2012

Followed recipe to the letter.  After refrigeration for over 4 hours, when cut into, the filling will not hold its shape, sort of pudding consistency not like jello consistency.

Answers:
Dan

it would depend on the recipe of the filling. I'm only guessing but I suspect that its a curd set with either eggs and butter or with cornstarch (or some other thicker).
It probably needed to be cooked more before you put it into the shell to set.
post the recipe and I'll be able to troubleshoot it better