Crank no start afraid to leave this battery hooked up?

I bought new battery which kept dying brought back and had a dead cell got new battery and my van will crank over but stall under a load. I've replaced distributor cap sensor, throttle position sensor, plugs and wires, distributor cap, fuel filter and there was a slow clicking noise under the dashboard by where you check your service engine area with old battery to afraid to leave this battery hooked up. Please help