Stuck in Deathspank and in need of help.

I have done lots of quests in the game and now the only quests left are the ones that require me to go past the rail bridge to Wortten's factory , the problem is that the road to Wortten's factory is closed and I couldn't deliver the acid that the engineer gave me , am I missing something? or is it a game bricking glitch?

I wish that you help me with this one and thanks in advance.