I made a beer 2 weeks ago and had 2 liters of yeast starter I made for it. I used about 1.5 liters and saved the rest for later in a sanitized jar in the fridge. Is the starter still fine? Is there anything I need to do before using it again?
The starter is still good in that time. Very roughly, a 2L starter, presumably from a vial or smack pack, probably netted you between 200bn and 400bn cells. If you used 3/4 of it, you probably have 50-100bn cells left … about the amount in a smack pack/vial. As such, you should probably make a new starter from the remains of the previous one.