Engine power supply system (VAZ-1111)

The fuel system includes devices for feeding fuel and air to the carburetor, preparing the combustible mixture and releasing exhaust gases. The fuel system consists of a fuel tank, fuel pump, fuel lines, air filter, carburetor, mufflers and pipelines.



The fuel for the engine is high-octane gasoline grade AI-93 with an octane number of 93, determined by the research method.

Fuel tank

Fuel tank 38 — stamped, welded from two steel halves. To increase corrosion resistance, the tank is tinned with POS 35 on both sides and painted with black enamel. The capacity of the fuel tank is 30 l, including the fuel reserve.

The tank is installed under the body floor and is secured with four nuts to the welded bolts of the body. On the side of the main muffler and exhaust pipes, the tank is covered with a screen that protects the fuel in the tank from heating. The filler neck 16 of the tank is brought out into a niche in the rear part of the right side of the body and is closed with a sealed plastic plug 14. The plug has a tightening torque limiter (some cars may have a lock installed in a traffic jam). The filler neck is connected to the fuel tank pipe by a hose 18 made of petrol-resistant rubber.

To prevent fuel from leaking out during refueling, the upper part of the filler pipe is connected to the tank branch pipe by a rubber hose 13, through which air is forced out of the tank during refueling.

Fuel level sensor 37 with fuel pickup pipe is attached to the fuel tank from above through a sealing gasket. Fuel pickup pipe has mesh filter 36. When there is fuel left in the tank, float lever 35 closes the contacts of fuel reserve indicator lamp. Fuel level indicator with fuel reserve indicator lamp is installed on the instrument cluster in the car interior.


For ventilation and access to atmospheric air, the fuel tank has a ventilation hose 12 made of a PVC tube with a tip 34 at the end. The hose is connected to the tank branch pipe, has a loop along the filler neck and is then laid on hooks along the rear edge of the tank. Fuel that gets into the lower part of the loop of hose 12 when the car is moving on an uneven road forms a liquid seal that prevents gasoline from evaporating from the tank.

Fuel lines and hoses

Fuel line 40, connecting the fuel tank with fuel pump 42, is made of galvanized or lead-coated steel tube with a diameter of 6 mm. Fuel line 40 is connected to the fuel tank and fuel pump by rubber hose 39 and 41. Rubber hose 43 connects the fuel pump to carburetor 44. Rubber hoses 39, 41 and 43 are fastened to the branches with screw clamps.

Fuel pump

The fuel pump is a diaphragm type, with a mechanical drive, equipped with a lever 9 for manual fuel pumping with an extension 8 of the lever. The fuel pump is mounted on two studs of the drive housing from the side of the front shield of the body through a heat-insulating spacer 3 and adjusting linings 1 and 2.

The pump is driven by pusher 4 from camshaft eccentric 5. The fuel supply by the pump is not less than 50 l/h at a pumping frequency of 2000±40 rpm. The pressure developed by the pump is 21...30 kPa.

The fuel pump consists of a lower housing 20 with drive levers, an upper housing 23 with valves and pipes, a diaphragm unit and a cover 24.

The diaphragm unit has three diaphragms: two upper 28 — working for fuel supply, one lower 30 — safety, working in contact with crankcase oil and preventing fuel from entering the engine crankcase if the working diaphragms are damaged. Between the working and safety diaphragms, remote outer 29 and internal 27 gaskets are installed. The external gasket has an opening for fuel to exit if the working diaphragms are damaged. The diaphragms with plates and with an internal remote gasket 27 are installed on the rod 31 and secured from above with a nut.

The diaphragm unit is installed between the upper and lower pump housings. A spring is installed under the diaphragm unit on the rod. Rod 31 is inserted with a T-shaped tailpiece into the slot of balancer 32. This design allows the diaphragm unit to be removed from the fuel pump without disassembling it.

In the lower housing 20, levers 19 of mechanical fuel supply and balancer 32 are installed on the axis. In the lower housing, also on the axis with cam 11, lever 9 of manual fuel pumping is installed, which returns to the initial position under the action of a spring. Lever 9 has an extension 8 to facilitate fuel pumping.

In the upper casing 23 of the pump there are installed textolite hexagonal suction 7 and discharge 8 valves. The valves are pressed against brass seats by springs. The cover 24 is fastened to the casing from above by a central bolt. A plastic mesh filter 25 of the pump is installed between the cover and the casing. The suction 26 and discharge 21 branch pipes are pressed into the upper casing of the pump.

When the engine is running, the camshaft eccentric 5 acts on the lever 19 via the pusher 4 and turns the balancer 32, which pulls the pump diaphragms down by the rod 31. In this case, the diaphragm spring is further reduced, a vacuum is created in the working chamber above the diaphragm unit, as a result of which the fuel fills the working chamber through the suction valve 7. When the eccentric runs off the pusher, the lever 19, balancer 32 and rod 31 with the diaphragms are released. The diaphragms, under the action of the compressed spring, create fuel pressure in the working chamber, the suction valve 7 closes, and the fuel is fed through the discharge valve 8 into the float chamber of the carburetor.

At low fuel consumption the diaphragm stroke will be incomplete; in this case, the stroke of lever 19 will be partially idle.

When manually pumping fuel through extension 8, press lever 9, cam 11 acts on balancer 32 and pulls rod 31 with diaphragms. Fuel is sucked into the working cavity. When released, lever 9 with extension and cam under the action of spring 10 return to their original position, and the diaphragms pump fuel into the carburetor.

When installing the fuel pump on the engine, adjusting linings 1 and 2 are selected in such a way that the minimum protrusion of the pusher 4 above the mating plane of the heat-insulating spacer 3 (taking into account the gasket between the spacer and the fuel pump) was 0.8...1.3 mm. The minimum protrusion of the pusher is set by slowly turning the engine crankshaft.

Gaskets 1 are made in three types and have a thickness of 0.30; 0.75 and 1.25 mm. An adjusting gasket 2 with a thickness of 0.30 mm must always be placed between the heat-insulating spacer and the fuel pump drive housing.

To determine the serviceability of the fuel pump, disconnect hose 43 from the pump discharge pipe and use lever 9 for manual fuel pumping to check whether fuel is supplied. In this case, the crankshaft should be in a position in which the stroke of lever 9 is complete. If fuel is not supplied, then disconnect hose 41 from the pump suction pipe and check whether a vacuum is created at the inlet of this pipe. If there is a vacuum, fuel line 40 or hoses 39 and 41 may be damaged or clogged. If there is no vacuum, the fuel pump is faulty. To eliminate the malfunction, it will be necessary to remove and disassemble the pump.