I have a 1995 E300D which has a deisel leak. It started with the injection pump and seems to be moving around. The next leak fuel filter shutoff valve, the hose "o" rings, etc. It seems to happen when it is hot and in Houston that's common. I've replaced pretty much every gasket and "o" ring. When I fuel up the fuel cap lets off quite a bit of pressure. My question is: is there a fuel pressure relief/return somewhere that I am missing?