Rule #1: Stay alive
If your support keeps feeding, you unfortunately can't do much about that. Of couse you can try to protect him and/or follow his engages, but if this would just end in you dieing too it would be the worst thing to do.
Rule #2: Don't overestimate yourself
You by yourself alone can't do much without a support. It already requires a lot of skill to sustain and keep on with CS on a 1vs2 Botlane. And if the opposing champions are even ahead of you, because they killed your support a couple of times it's even harder. Don't try to make things up in some heroic action, you will just die and give them even more advantage.
Rule #3: Stay calm and CS
As long as you don't get ganks you have to play passively. Just try to keep up at least a bit with the CS without getting yourself killed. In doubt just tower hug and take the last hits you can get there - even if you fall behind with CS then. In doubt ask the jungler if you can take Golems or Wolves (depending on your side of the map).
Rule #4: Ask for ganks
If the jungler doesn't come by himself ask for ganks. There is nothing wrong with that - if he's at least a half decent jungler he won't let you beg for them. Also your situation gives you one advantage -> most likely your lane will be pushed constantly, which means your jungler should have an easy time ganking. If your enemies are too strong you maybe even want to ask your AP Carry to help you release some pressure on your lane too.
Rule #5: Don't give up
Even if your team doesn't manage to gank your lane propery - don't give up. Maybe the other lanes are doing fine and will carry the game. But if you give up, your team lost it's support and it's AD Carry which will seal the defeat for your team.