OM606- Sanity check fuel line air leaks
OM606- Sanity check fuel line air leaks
Sorry to hear you are still having problems with this system. It really is terribly designed.
There are o-rings around the delivery valves. They usually get enough pressure that they leak visibly once they are a problem. Also the fuel heater itself has a seal between the plastic and metal parts.
If the problem is on the suction side. Get the engine started, then partially restrict the inlet hose (vice grips). Shine a bright flashlight through the clear lines. Often you can see where the bubbles start.