What you are referring to as the "jet" is actually a check valve to keep pressure in the system after shut down. As you have found--it can be tricky to get the whole assembly tight enough not to leak. The '84 245Ti I'm currently cleaning up had a regular drip-drip from the pump area when my daughter looked at the car for me. While the fuel line was tight to the check valve--the check valve was loose to the pump. Use fresh copper rings and tighten the heck out of it--counter holding the pump when installing the CV--and then counter holding the CV when attaching the fuel line. -- Dave