Cause | Elimination Method |
Engine won't start | |
No fuel in carburetor: | |
– clogged fuel lines or carburetor and fuel pump filters | – wash and blow out the fuel tank, fuel lines and filters |
– the fuel pump is faulty | – check pump operation and replace damaged parts |
Faulty ignition system | See subsection 5.4 |
The carburetor choke remains closed at the first flashes in the cylinders | Repair leaks in carburetor starter |
Engine runs erratically or stalls at idle | |
Engine idle adjustment is broken | Adjust idle |
Air leak through a damaged drain tube | Replace drain tube |
Air leakage through gaskets in the intake manifold connections to the carburetor or cylinder head | Tighten fastening nuts or replace gaskets |
Violated gaps between the levers and camshaft cams | Adjust gaps |
Faulty carburetor: | |
- jets or carburetor channels are clogged | – blow the jets and channels with compressed air |
- water in the carburetor | - remove water from the carburetor, drain sediment from the fuel tank |
- the tightness of the diaphragm of the starting device is broken | change diaphragm |
Faulty ignition system | See subsection 5.4 |
The engine does not develop full power and does not have sufficient throttle response | |
Incomplete opening of the throttle valves of the carburetor | Adjust throttle actuators |
Air filter dirty | Replace filter element |
Faulty ignition system | See subsection 5.4 |
Faulty fuel pump | Check pump operation and replace damaged parts |
Faulty carburetor: | |
– faulty accelerator pump | – check pump performance, replace damaged parts |
- clogged main jets | - blow jets with compressed air |
- air damper not fully open | - adjust damper actuator |
– fuel level in the float chamber is not correct | - adjust the float setting |
Violated gaps between the levers and camshaft cams | Adjust gaps |
Insufficient compression - below 1 MPa (10 kgf/cm2): | |
- blown cylinder head gasket | - replace gasket |
– Burning of pistons, breakage or occurrence of piston rings | – clean the rings and grooves of the pistons from carbon deposits, replace the damaged rings and the piston |
– poor fit of valves to the seats | – replace damaged valves, grind seats |
– Excessive wear of cylinders and piston rings | – replace pistons, bore and honing cylinders |
Knocking crankshaft bearings | |
Usually a dull tone, metallic. Detected when the throttle is suddenly opened at idle. Its frequency increases with an increase in the frequency of rotation of the crankshaft. Excessive axial clearance of the crankshaft causes a sharper knock with uneven intervals, especially noticeable with a smooth increase and decrease in the crankshaft speed | |
Too early ignition | Adjust ignition setting |
Insufficient oil pressure | See below |
Loose flywheel bolts | Tighten the bolts to the recommended torque |
Increased clearance between journals and main bearing shells | Sand the necks and replace the liners |
Increased clearance between thrust washers and crankshaft | Replace thrust half rings with new ones or with increased thickness |
Knocking rod bearings | |
Usually the knock of the connecting rod bearings is sharper than the knock of the main bearings. It is heard at idle speed of the engine with a sharp opening of the throttle. The place of knocking is easy to determine by turning off the spark plugs one by one | |
Insufficient oil pressure | See below |
Excessive clearance between crankshaft journals and bearings | Replace liners and re-grind necks |
The knock of pistons | |
This knock is usually unvoiced, muffled: called «beating» piston in the cylinder. It is best heard at low engine speeds and under load | |
Increased clearance between pistons and cylinders | Replace pistons, bore and honing cylinders |
Excessive clearance between piston rings and piston grooves | Replace rings or pistons with rings |
Knocking inlet and outlet valves | |
Working with increased clearances in the valve train causes a characteristic knock, usually at regular intervals; its frequency is less than any other knock in the engine, since the valves are driven by a camshaft, the rotational speed of which is half the speed of the crankshaft | |
Increased clearances between levers and camshaft cams | Adjust gaps |
Valve spring failure | Replace spring |
Excessive clearance between stem and valve guide | Replace worn parts |
Camshaft lobes wear | Replace camshaft and valve levers |
Loosening the locknut of the adjusting bolt | Adjust the gap between the lever and the camshaft cam, tighten the locknut |
Excessive Camshaft Drive Circuit Noise | |
From the general noise of the engine, the noise of the camshaft drive circuit stands out when gaps appear between the gearing elements and is clearly audible at a low crankshaft speed. | |
Loose chain due to wear | Pull the chain |
Broken chain tensioner shoe or damper | Replace tensioner shoe or damper |
Jamming of the stem of the plunger of the chain tensioner | Eliminate the jam |
Entry under the pressure reducing valve of the oil pump of foreign particles | Clean the valve from foreign particles and burrs, flush the oil pump |
Worn oil pump gears | Repair oil pump |
Excessive clearance between bearings and crankshaft main journals | Sand the necks and replace the liners |
Seized oil pressure reducing valve | Replace valve |
The use of engine oil of an inappropriate brand and quality | Change the oil to another recommended subsection 14.3 |
Excessive oil pressure on a warm engine | |
Seizure of the reducing valve of the oil pump | Replace valve |
Increased oil consumption | |
Oil leakage through engine seals | Tighten fasteners or replace gaskets and seals |
Worn piston rings and pistons or engine cylinders | Rebore cylinders and replace pistons and rings |
Breakage of piston rings | Replace rings |
Coking of slots in oil scraper rings or piston grooves | Clean slots and grooves |
Worn or damaged valve stem seals | Replace oil seals |
Increased wear on valve stems or guide bushings | Replace valves, rebuild cylinder head |
Increased fuel consumption | |
Air damper not fully open | Adjust damper actuator |
Increased vehicle resistance | Check and adjust tire pressure, brake system, wheel alignment |
Incorrect ignition timing | Adjust ignition timing |
The vacuum regulator of the distributor of ignition is faulty | Replace vacuum regulator or ignition distributor |
High fuel level in the carburetor: | |
- the tightness of the needle valve or its gasket is broken | – check for foreign particles between the needle and the valve seat, if necessary, replace the valve or gasket |
- jamming or friction that prevents the normal movement of the float, leakage of the float | – check and, if necessary, replace the float |
Clogged carburetor air jets | Clean the jets |
Engine overheating | |
Poor tension on the pump and alternator drive belt | Adjust belt tension |
Insufficient amount of fluid in the cooling system | Add coolant to the cooling system |
Incorrect ignition timing | Adjust ignition timing |
The outer surface of the radiator is heavily soiled | Clean the outer surface of the radiator with a jet of water |
Faulty thermostat | Replace thermostat |
Faulty radiator plug valve (opening pressure less than 0.05 MPa (0.5 kgf/cm2) | Replace plug |
Faulty coolant pump | Check pump operation, replace or repair |
Rapid drop in fluid level in expansion tank | |
Damaged radiator | Repair or replace radiator |
Damage to hoses or gaskets in pipe connections | Replace damaged hoses or gaskets |
Fluid leaking from heater tap | Replace faucet |
Loose hose clamps | Tighten the clamps |
Fluid leakage through the coolant pump seal | Replace seal |
Damaged radiator cap or gasket | Replace plug |
Damaged cylinder head gasket | Replace gasket |
Liquid leakage through microcracks in the block or in the cylinder head | Check the tightness of the block and cylinder head, if cracks are found, replace damaged parts |
Fluid leakage through microcracks in the housing or cover of the coolant pump, expansion tank or inlet pipe | Check the tightness, if cracks are found, replace the damaged parts; an insignificant leak can be eliminated by adding a sealant type NIISS-1 to the coolant |