I have a 91 RS which I had to jumpstart the other day to get going. The car ran fine coming home, but after going in the house for about an hour and coming back out I turned the key and nothing at all. I just took the battery out and checked it, which it turns out it's fully charged. I'm not sure where to go from here. Thanks.

 

More info would be helpful. i.e. Trans type, how did you check the batt? voltage test? Current Draw test? More information gets better answers.

Things to check are Ground wire at engine block for bad connection.
Clutch start switch, if it's a stick.
VATS System, Does the security light come on when you try and start it?
VATS- Starter enable relay, located by the fuse box. if it activates VATS is OK but check it for voltage on the starter side. both if you don't know which is the starter side.
Crank fuse
Ign switch.
Starter Sol.
Starter enable switch, same as neutral safety switch located in the console on the shift mechanism.
A voltage drop test can be very useful in locating the problem. Place the positive lead of your voltmeter on the side of the circuit that is closest to the pos. batt terminal The negitive on the other side of the component that is being tested. have some one turn the key to start. The higher the voltage reading the more resistance there is, near batt voltage is a failed component.
For example put pos. test lead on the pos. side of the starter enable relay The negative can go on the starter side of the relay (the 2 heavy gauge wires) or on the starter sol. terminal. (the one from the key switch) have some one turn the key to start. You can use this to test singe components or to check parts of a circuit to see where the fault is. i.e. neg. to starter side of the relay would check just the relay. neg to the starter sol would check the circuit including the Relay. pos. batt. post to pos. batt terminal would check just the connection at the post and the terminal. (with key turned to start position) just remember the circuit has to be live (voltage put to it) to do the check.
if you have a digital volt meter polarity is not important, just the voltage reading.
to check the starter sol, pos. to the terminal coming from the key switch neg to ground on the starter with your volt meter. have some one turn the key to start. A reading of battery voltage would mean a bad sol.

I had a batt go bad once on a 3 mile ride to the gas station. Voltage was 13.2 no load, if I turned the headlights on it would drop to 0. one of the cell connectors went bad on the ride to the gas station or when I started the truck. so if you haven't done it yet do a current draw test on your batt. it's the simple things that get you every time!
Hope this isn't to confusing and that it helps. I just went through this with my 92RS.

 

The Vats have been bypassed, so thats not it. What I mean by nothing is that when I turn the key forward I don't get power to anything, no lights in the dash or anywhere else. I tested my battery by hooking it up to my charger and it reads as 100%. As far as the starter goes it is brand new. The clutch switch is good. I have checked the battery connections and they are tight. I do not have a Multimeter, but will go get one. I have a feeling my charger is lying to me, so I'm going to take the battery to a battery shop.

 

make sure all you wires on you starter are tight and not corrroded mine did that before. and check your battery connection real good, sometimes it doesnt take much to lose connection. also could be the ign switch, the one on the clumn with the connections to it.