Depending on the engine model, various versions of the K-151 carburettor are used, differing in the flow sections of the jets and in minor design changes.
The K-151 family carburettor is of the emulsion type, two-chamber, with downflow and mechanical sequential opening of the throttle valves.
External views of the carburettor: 1 — float axle screw plug; 2 — threaded plug of the fuel jet of the second chamber transition system; 3 — vacuum take-off union to the ignition distributor vacuum regulator; 4 — vacuum take-off union to the solenoid valve of the EPHX system; 5 — crankcase ventilation system union; 6 — union bolt; 7, 29 — fuel supply union; 8 — air valve drive lever; 9 — air valve; 10 — threaded plug of the emulsion jet of the idle system; 11 — accelerator pump; 12 — economizer body; 13 — vacuum control union of the exhaust gas recirculation valve; 14 — idle mixture composition adjusting screw (quality screw); 15 — idle crankshaft speed adjusting screw (quantity screw); 16 — adjusting screw securing the overlay lever of the starting device control cam; 17 — two-arm lever of the starting device; 18 — air valve axle lever; 19 — air valve drive rod; 20 — microswitch of the EPHX system; 21 — sector (throttle valve drive lever); 22 — sector free travel tension spring; 23 — overlay lever of the starting device control cam; 24 — second chamber throttle valve lever; 25 — second chamber valve lever stop screw; 26 — starting device cam; 27 — air valve closing lever; 28 — air valve closing spring; 30 — accelerator pump drive cam; 31 — vacuum supply union to the economizer valve.
The carburettor is secured to the intake pipe by four studs through two paronite gaskets, between which a stamped steel tray is fitted.
The carburettor consists of three parts: the cover, the body and the throttle valve body.
The carburettor has:
- main metering systems of the first and second chambers;
- idle system and transition system of the first chamber;
- transition system of the second chamber;
- econostat;
- accelerator pump;
- starting device;
- forced idle economizer (EPHX) system.
Carburettor diagram: 1 — cover; 2 — float; 3 — air jet of the second chamber transition system; 4 — fuel jet of the second chamber transition system; 5 — threaded screw holder of the econostat atomiser; 6 — main air jet of the second chamber; 7 — econostat atomiser; 8 — emulsion tube of the second chamber main metering system; 9 — small diffuser of the second chamber with atomiser; 10 — delivery valve; 11* — accelerator pump atomiser; 12 — air valve; 13 — small diffuser of the first chamber with atomiser; 14 — main air jet of the first chamber; 15 — emulsion tube of the first chamber main metering system; 16 — block of fuel and air jets of the idle system with emulsion tube; 17 — emulsion jet of the idle system; 18 — idle air jet; 19 — adjusting needle on the jet of the accelerator pump drain channel; 20 — travel limiter of the accelerator pump ball valve; 21 — carburettor body; 22 — bypass (drain) jet of the accelerator pump; 23 — ball of the accelerator pump valve; 24 — accelerator pump diaphragm spring; 25 — accelerator pump diaphragm; 26 — accelerator pump diaphragm cover; 27 — accelerator pump drive lever; 28 — main fuel jet of the first chamber; 29 — EPHX valve union; 30 — EPHX valve diaphragm; 31 — EPHX shut-off valve; 32 — plastic rotation limiter of the quality screw; 33 — idle mixture composition adjusting screw (quality screw); 34 — relief sub-diaphragm hole in the EPHX valve body; 35 — forced idle economizer body (idle assembly); 36 — seat of the idle system valve; 37 — idle crankshaft speed adjusting screw; 38 — gasket; 39 — additional mixture composition adjusting screw on the main fuel supply branch of the idle system (only on early carburettor versions); 40 — transition slot hole of the idle system; 41 — first chamber throttle valve; 42 — accelerator pump lever drive cam; 43 — accelerator pump lever roller; 44 — inlet window of the idle system air channel; 45 — second chamber throttle valve; 46 — heat-insulating laminated gasket of the carburettor body; 47 — throttle valve body; 48 — vacuum take-off union to the EPHX control solenoid valve; 49 — vacuum take-off union to the ignition advance vacuum regulator; 50 — main fuel jet of the second chamber; 51 — vacuum take-off union to the exhaust gas recirculation valve; 52 — power circuit of the EPHX control unit; 53 — microswitch circuit of the EPHX system; 54 — filter on the ventilation union of the EPHX control solenoid valve; 55 — solenoid valve of the EPHX system; 56 — union bolt; 57 — fuel filter; 58 — fuel supply union; 59 — plug on the float chamber wall; 60 — shut-off valve of the float mechanism; 61 — eye of the shut-off needle; 62 — float tongue. On carburettors fitted to the 2.5 l engine, the atomiser has a single nozzle directed into the first chamber.
The float chamber is balanced, with a plastic float.
Fuel is supplied to it through a mesh filter. The float mechanism has a needle valve.
The float acts on the valve needle, closing the channel and thereby maintaining the required fuel level in the float chamber. There is no fuel return to the tank.
The main metering system consists of air and fuel jets, emulsion tubes and atomisers fitted in the small diffusers of the carburettor chambers.
The idle system is autonomous, with adjustment of the mixture quantity and composition by the quantity and quality screws.
The idle system is provided with a forced idle economizer (EPHX) that cuts off the fuel supply in the engine braking mode. This reduces harmful emissions and lowers fuel consumption.
The transition systems of the first and second chambers operate at the moment their throttle valves open and ensure smooth engagement of the chambers.
The transition system of the first chamber is combined with the idle system.
The carburettor econostat, under the action of vacuum, supplies an additional amount of fuel through the atomiser into the second chamber at maximum power modes.
The accelerator pump is of the diaphragm type, driven from the axle of the first chamber throttle valve.
When the throttle valve is opened sharply, it enriches the mixture by injecting an additional portion of fuel into the first chamber of the carburettor, which ensures the vehicle's responsiveness.
In the carburettor of the 2.9 l engine, the accelerator pump atomiser has two nozzles supplying fuel to both chambers.
The starting device is of the semi-automatic type and consists of a pneumatic corrector, a lever system and the air valve.
The air valve must be closed before starting a cold engine using the manual drive.
At the moment of engine start, the pneumatic corrector, under the action of the vacuum generated in the intake pipe, automatically opens the air valve by the required angle, ensuring stable engine operation during warm-up.
Design features and maintenance recommendations
Materials used and recommendations
- Paronite gaskets — use when fitting the carburettor; a stamped steel tray is fitted between them.
- Mesh filter — check and wash during float chamber maintenance.
- Needle valve of the float mechanism — check tightness and wear; replace if necessary.
- Jets — when replacing, select the flow section according to the engine model.
- Quality and quantity screws — use to adjust the mixture composition and idle speed.
- EPHX — check the operation of the solenoid valve and microswitch; a fault may cause increased fuel consumption.
- Pneumatic corrector of the starting device — check tightness and free movement of the levers.
- Accelerator pump diaphragm — check for elasticity and absence of cracks.