Bukkit

What steps will reproduce the problem?
1. place ironblock
2. place rail above it
3. place a sign under the iron block with
1st line: [empty:l]
2nd line: [player:r]
4. use tool, sneak and punch it. The rail is dstroyed and it says "block added" in the chat
5. i place the rail again
6. i let a minecart pass it, and every cart, full and empty wil drive right(south/west rule)

What is the expected output? What do you see instead?
Every cart drives right, but i want that an empty cart drives left

What version of the product are you using?
0.4

Do you have an error log of what happened?
no

Please provide any additional information below.
booster blocks are working perfectly