The Fuel Supply Line

The higher viscosity of SVO as compared with peytroleum diesel causes it to flow less readily through the fuel supply line. For this reason, Elsbett installs a larger diameter fuel supply line from the tank to the engine compartment. This installation seemed easier on the Mercedes cars at the workshop, since the tank connections were accessible from under the car. For TDIs, the connection originates on top of the tank under the rear passenger seat. In either case, most of the length of the new supply line is a semi-rigid plastic tube, but at each end, it switches to a flexible rubber-like tube for easier routing to the tank and engine compartment connections. The connections to the rigid plastic tube appeared to be one of the most mechanically difficult parts of the conversion. In general, the metal hose-barbed connector is heated either with propane torch or electric heat gun, and then the plastic tube is forced onto the barbs until they penetrate to the limits of the connector. It helps to gently heat the plastic tube as well, and it is also easier to clamp the connector in a vise or at least brace it against the floor or other solid object while pushing the tube on. When installing the rubber-like hose on the same barbed connector or other connectors, Alexander sprays a bit of WD-40 inside the end of the hose first.

By the way, Kent says to remind everyone to place clamps over the hoses BEFORE you join the hose to the connector!

Alexander contemplates Kent's Jetta with the rear seat raised to get at the fuel tank connections.

Leif, Alexander and Kent looking for debris and deposits in Kent's fuel gauge sender unit. Later, they drilled out a check valve within this mechanism to further improve the fuel flow. Todd alerted us to the existence of this check valve in some Jetta models.

Kent feeds the new fuel line through a narrow gap beside the gauge sender unit, down to Alexander below. The hammer had a role in this process as well - Alexander used it and a long screw driver to "chisel" out a bit more clearance for the fuel line in a plastic trim piece. Without the extra clearance, the fuel line tends to get pinched when the tank straps are re-tightened.

Here's Alexander trying to retrieve the fuel line that Kent is pushing down. Note the loose fuel tank strap, that allows a bit of extra clearance while installing this fuel line.

Got it! Now comes the hard part--joining this rubber-like hose to the more rigid plastic line that goes up to the engine compartment.

Kent watches Alexander push the plastic tube onto the hose barbs after heating both gently. This would become the connection inside the engine compartment. Unfortunately, the other end had to be installed in place under the car. First, they routed the tube from the engine compartment through the channel back to the fuel tank. Then they cut the tube to the correct length and then lowered the car so Alexander could...

...heat the fitting...

and then brace the fitting against the floor while he pushed the tube onto it.

Raising the car again, they connected the plastic tube to the rubber-like hose and installed clamps.

Finished view from fuel tank looking forward - note the larger diameter of the new line, and the tie-wrap securing it in place.

Later, Kent helped Todd do the same process on Todd's Golf. Kent shows how easy it was!

Meanwhile, Rachel and Pete drain Mimi's Mercedes fuel tank...

...and plan the fuel line route to the engine compartment...

Which Mimi and Andy follow with ease.

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