1985 300sd fuel tank vent valve

[jack avant]

My fuel tank is building up pressure. My question is can I remove this vent with fuel in tank. I would think that it needs cleaning. Help please. It built up so much pressure that a hose before the primary filter started leaking.

[Biodiesel300TD]

You probably have a bad hose and that is why it's leaking. Not too much pressure.

You shouldn't be getting pressure in the tank. The system sucks out of the tank. If the vent is clogged you get vacuum in the tank and will starve the engine eventually. This can be diagnosed by removing the fuel cap after driving a bit. If you get a suction sound then the vent is clogged. The 123's have a little bell shaped rubber piece under the car that is on the end of the vent line, it can get clogged. Not sure if the 126's have one, if they do, try cleaning that out and see if that changes anything. It's in the rear. Just follow all the metal lines back there until you find one with a bell shaped rubber piece.