Connecting a transistor base directly to a bidirectional port pin of a standard 80C51 is no good idea because you force the port pin to a rather low potential there. Inside the port driver there is a circuit, which detects this low level and turns off the output driver. This to reduce supply current when the port pin is used as an input. So, with your different loads (LED, relay) the one time this base resistor adding might work and the other time might not.

Don't turn on a load with a logic high at the port pin!! The one reason is that the standard 80C51 port output isn't strong enough the provide enough current. The other reason is that logic high at the ports is also the reset level of a standard 80C51. So, use a driver which needs a logic low to turn on your load as Michael has mentioned already.

Kai Klaas