Introduction to Automobile Oil Return Pipe

Abstract:

The function of a vehicle's oil return line: It allows excess oil to return to the tank, reducing fuel consumption. Not all vehicles have an oil return line. Return Line Filter […]

The function of a vehicle's oil return line: It allows excess oil to return to the tank, reducing fuel consumption. Not all vehicles have an oil return line.

The return line filter is installed in the hydraulic system's oil return line to remove metal powder and rubber impurities from worn components, ensuring clean oil returning to the tank.

The filter element is made of synthetic fiber and offers high filtration accuracy, high oil flow capacity, low initial pressure loss, and a high dirt holding capacity. It is also equipped with a pressure differential indicator and a bypass valve.

When the filter element becomes clogged to a pressure differential of 0.35 MPa between the inlet and outlet, a switch signal is issued, indicating the need for cleaning or replacement. If the system is not shut down promptly or no one is present to replace the filter element, the bypass valve located above the filter element automatically opens to protect the system. This filter is widely used in hydraulic systems of heavy machinery, mining machinery, metallurgical machinery, and other applications.

Most modern vehicles have a fuel return line. After the fuel pump supplies fuel to the engine, building up a certain pressure and supplying the fuel injectors with the remaining fuel, the remaining fuel is returned to the fuel tank through the return line. Of course, excess gasoline vapor collected in the carbon canister also returns to the tank through the return line. The return line returns excess fuel to the tank, relieving gasoline pressure and reducing fuel consumption.

Diesel engine fuel supply systems typically have three return lines. Some diesel engine fuel supply systems only have two return lines, without a return line from the fuel filter to the tank.

Return Line on the Fuel Filter

When the fuel pressure provided by the fuel pump exceeds 100-150 kPa, the overflow valve in the return line on the fuel filter opens, allowing excess fuel to flow back to the tank through the return line. Fuel return line on the injection pump

Since the fuel pump's delivery capacity is 2-3 times the maximum fuel delivery capacity under the injection pump's rated operating conditions, excess fuel flows back to the fuel tank through the return line.

Fuel return line on the injector

During operation, a very small amount of fuel leaks from the mating surface between the needle valve and the valve body. This acts as a lubricant to prevent excessive accumulation and needle valve back pressure, which could lead to malfunction. This fuel is directed through the hollow bolt and the return line to the fuel filter or fuel tank.

Troubleshooting:

The return line is a relatively unnoticeable component in a vehicle engine, but it plays a vital role in ensuring proper engine operation. The return line's layout in a vehicle is quite unique, and leaks or blockages can cause a variety of unexpected problems. The fuel return line is a valuable window into engine troubleshooting, allowing for a variety of ingenious inspections and diagnosis. The basic inspection method is as follows: Disassemble the return line for inspection to quickly determine the fuel system's operating condition. To determine whether the fuel pressure in an electronic fuel injection engine's fuel system is normal, if a fuel pressure gauge is unavailable or difficult to access, you can indirectly determine this by observing the return flow from the return line. Specifically (using a Mazda Protégé as an example): disconnect the return line, start the engine, and observe the return flow. If the return flow is rapid, the fuel pressure is generally normal. If the return flow is weak or absent, it indicates insufficient fuel pressure, requiring inspection and repair of components such as the electric fuel pump and fuel pressure regulator. (During this inspection, use a hose to direct the fuel flowing out of the return line into a container to prevent contamination and fire.)