2000 Volkswagen TDI Fuel delivery problem

DKLIEWER

MEMBER
2000 VOLKSWAGEN JETTA TDI
4 CYL
FWD
AUTOMATIC
120,000 MILES

I have a jetta 2000 TDI automatic that has an air in the fuel delivery hose problem. I replaced the existing neoprine tubing with transparent tubing to view since I suspected air leak issues. When the car is running, I observed bubbles from the tank supply feed, as well as from the filter to basically the entire fuel supply and return tubing. I bypassed the return valve on the filter, allowing the return gas line to flow directly back to the fuel tank, and stoppered the return valve seat on the filter, only to find more bubbles in the supply hose to the filter.

I am suspecting that the problem lies somewhere in the feed line from the tank to the filter; my questions are: what components comprise the fuel supply system from the tank to the filter - which of these components are likely to fail? How is the tank constructed? Is it possible that the leak originates inside the tank?

My best guess is that the right-angle press-on connectors are at fault, but I suspect there may be other components that could be suspect.

1 Reply

MATHIASO

MECHANIC
1,209 POSTS

Your car should be equiped with a fuel filter water seperator.

Diesel fuel and water do not readily mix, fuel does tend to entrap moisture from the air each time it is moved from one container to another. Eventually every Diesel fuel system collects enough water to become a potential hazard. Fortunately, when it's allowed to settle out, the water will always drop to the bottom of the tank or filter housing. Some Diesel fuel filters are equipped with a water drain; a bolt or petcock at the bottom of the housing.

If the filter is equipped with a water drain at the bottom, place a pan under the drain to catch the water and fuel.
If equipped, loosen the vent bolt on the filter base. If there is no vent, loosen the return line at the pump (the line not connected to the filter).
Loosen the bolt or valve. When fuel flows in a clean stream, close the drain and tighten the vent or return line.

On most diesel fuel filters, a water drain screw (bottom) is provided for bleeding any accumulated water from the fuel system

here is the fuel system component you requested.