Multipoint - EFI System (Part6. FUEL RETURN CIRCUIT)

The fuel return circuit is made up of all the components that carry fuel from the outlet of the pressure regulator to the fuel tank, Fig.Below. This normally includes rub­ber fuel hoses, a steel fuel line, and necessary fittings.

The fuel return circuit allows circulation of fuel through the main fuel line, fuel rail, past the inlet to the injectors, through the regulator, return line, and back to the tank. This circulation prevents a heat buildup in the fuel. Heat could cause bubbles in fuel, upsetting fuel mixture.

Fuel Accumulator

A fuel accumulator dampens fuel pressure pulses and helps maintain fuel pressure when the engine is shut off. Fuel pressure fluctuations result from the action of the fuel pump and from the injectors constantly opening and closing. Too much pressure fluctuation could upset the operation of the pressure regulator.
The fuel accumulator acts like a "shock absorber." It can increase component life and help quiet system operation.
The fuel accumulator is simply an enclosed container with a spring-loaded diaphragm. Fuel pressure pushes the diaphragm down and compresses the diaphragm spring. This provides energy to maintain pressure or to counteract a sudden pressure drop.

Fuel accumulator is simply a small canister fitted with fuel inlet and outlet. Canister contains a spring and a diaphragm, the spring and diaphragm absorb pressure pulsations like a cushion. Left. Note names of parts. Center. When engine is running, fuel pressure compresses diaphragm spring. Right. When engine is stopped, spring presses up on diaphragm to maintain system pressure. (Volvo)