General Description

Fuel Supply
An electric transfer pump, located in the fuel tank, pumps fuel from the tank to the fuel reservoir where it can be picked up by the main electric fuel pump. The main pump supplies fuel under pressure to the fuel injection system. If, for any reason, electric power to run these pumps is interrupted, the engine will not run.

Fig. 4-1 shows the fuel reservoir, together with the main fuel pump, the fuel filter, and the fuel accumulator used on CIS, CIS-E and CIS-E Motronic systems. Digifant models are similar, but do not include the accumulator.

Absolute cleanliness is essential when working with the fuel system. Even a minute particle of dirt can cause trouble if it reaches an injector. Thoroughly clean the unions before disconnecting any of the fuel line connections. Use only clean tools. Keep removed components clean, and seal or cover them with a clean, lint-free cloth, especially if the repair cannot be finished immediately. When replacing parts, install only new, clean components. Avoid the use of compressed air nearby, and do not move the car while the fuel system is open. Seals, 0-rings, and clamps should always be replaced rather than reused.

Fig. 4-1:

Fig. 4-1. Fuel reservoir, main fuel pump, fuel filter, and accumulator on CIS, CIS-E, and CIS-E Motronic systems. Reservoir and pump assembly on models with Digifant is similar,

Fuel Pump:
The electric fuel pump is mounted in the fuel reservoir. The pump is cooled by fuel and therefore may be damaged if allowed to run dry. The pump runs whenever the ignition switch is in the start or run position and the engine is turning over or running. The important fuel pump performance measurements are fuel pressure and volume of fuel flow. Another important aspect of fuel system performance is residual pressure-the pressure which is maintained in the system after the engine is off to aid hot-starting.

On cars with CIS, CIS-E, and CIS-E Motronic, residual fuel pressure is maintained by the fuel accumulator, located on the side of the fuel reservoir and shown in Fig. 4-6, and by a fuel pump check valve. On these cars, the fuel pump check valve is replaceable.

Fig. 4-6:

Fig. 4-6. Schematic cross-section of fuel accumulator to damp pressure pulses and maintain residual pressure in CIS, CIS-E, and CIS-E Motronic systems.

On cars with Digifant, residual pressure is maintained by a One-way check valve at the fuel pump outlet, and a one-way heck valve in the fuel pressure regulator. The fuel pump heck valve is not replaceable.