Shahzad,

You said:
.... i connect the LED to 89c51 port pin and ground directly with positive to port pin. its too dim i was expecting it bright... it usually was with 89c2051 port pin.

I think:
This is not an usual way to connect a LED. In this way the LED has to light when the output pin is high, and the high level output current use to be very loy, maybe 0.5 mA.

Alternatives:
1) Connect the LED cathode to the port pin and the LED anode to +5V via a 1k5 resistor. So yu get about 2 mA. Not very bright and the output current is at its limit value. Valid for test purposes. With
an 89C2051 you can use a resistor of about 330 ohm and get about 10 mA, valid for a real project.

2) Use a transistor to drive the LED. Recommended for a real project using the 89C52.

BTW:
What port is the LED and/or the LCD connected to?.
Are you sure the EA pin is connected to +5V?.

Alfredo.