Fuel and Vacuum Line Routing (1985.5 and Newer N/A 944s)

Introduction

This page describes the fuel and primary vacuum line routing for 1985.5 and newer 8V normally-aspirated 944 models. Additional vacuum routing exists for the heater control valve and ventilation controls; that routing is common across all 944 variants and is not covered here.

Fuel Lines

The fuel system is a circulating type: the pump moves more fuel than the engine consumes, and the excess returns to the tank.

• Supply. The in-tank fuel pump draws from the tank and pushes fuel forward through the fuel filter to the engine compartment. On 1985.5 and newer cars the supply line connects to the fuel damper at the front of the fuel rail; the damper smooths the pressure pulsations created by the fuel injectors. From the damper, fuel enters the fuel rail, which feeds each of the injectors.
• Return. At the rear of the fuel rail, the fuel pressure regulator bleeds off the excess and sends it back through the return line to the tank. The regulator is what sets the rail pressure.

Vacuum Lines

The primary vacuum connections on these cars are:

• Fuel pressure regulator. A vacuum line runs from the intake manifold to the regulator so that rail pressure tracks manifold vacuum — keeping the pressure drop across the injectors constant as load changes.
• Brake booster. A large vacuum line feeds the brake booster from the intake manifold.
• Evaporative charcoal canister. A line connects the fuel tank's vapor system, through the charcoal canister, to the intake — purging stored fuel vapor into the engine.

The throttle body and intake manifold also carry the smaller vacuum taps used by the idle and crankcase-ventilation systems.