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Diagnosis of common mechanical failure Engine

Misfire occurs when the engine is idling

Most often, an engine misfire occurs due to malfunction of power supply systems and / or ignition. If you find the cause of irregularities in the fault diagnosis of these systems fails, check the following options:

There are air leaks through a lining of the inlet pipeline. Check missed oil or desiccant pipe joints with the engine running and listen to the hiss, indicating the source of the leak.

Disturbed regulation valves (engines of 4.2 liters). Check, if necessary, make adjustments to the gaps.

Violating the integrity of the cylinder head gasket. Inspect compression pressure in the cylinders, if necessary, replace the gasket.

There is a burn-out trays or valve seats in the cylinder head. Check the compression pressure, if necessary, make a major overhaul of the head.

Broken or worn piston rings. Check the compression pressure, if necessary, replace the ring.

Loose or worn valve springs. Remove the cylinder head cover and check the condition of the valve springs.

To check the compression pressure unplug the ignition system and act in accordance with the instructions set out in the section on general settings of the engine (see. Chapter Settings and maintenance).

The valve mechanism is at work emits unusual noises

Broken adjustment of backlashes of valves (engines of 4.2 liters). Check, correct.

Loose or broken valve springs. Remove the cylinder head cover and check the condition of the valve springs. If necessary, replace.

Worn or damaged rocker arm assembly. Replace defective components.

Defective hydraulic pushers (engines of 3.0 liters). Replace defective pushers.

Worn valve guides. Perform overhaul of the cylinder head.

Worn cam lobe. Check the camshaft, if necessary, replace.

Before removing the camshaft cams for inspection, check the oil pressure and the condition of the valve springs and, if applied, hydraulic tappets.

We have the noise emitted by the bearings bottom heads of rods

Disrupted oil supply. Check the oil level in the sump and the state of the oil pump and relief valve. Replace the oil filter.

Excessive clearance in the bearings. Replace the pads, check the crank pins of the crankshaft, if necessary, their groove.

Fueled too liquid oil or its dilution occurred gasoline or water. Change the engine oil, the Gulf fresh varieties required. Try to identify and eliminate the cause of thinning.

Fell oil pressure. Check the pressure reducing valve, the state of the spring. Also, check the operation of the overflow valve of the oil filter.

There has been a shift of the connecting rod bearing. Correct rods, if necessary, replace liners.

When a fault rod bearing is usually caused metal knock intensity is maximum when the vehicle is moving at a speed of 60 km / h with a closed throttle. Before disassembling the engine to check the condition of the bottom heads of rods, check the measuring probe and the level of consistency of motor oil. Also, remove the gauge, oil pressure switch and screwed in its place a pressure gauge to measure the pressure.

We have the noise emitted by main bearings (obvious)

Flywheel is loose. Tighten bolts with demanded effort.

Fell oil pressure. Check the main bearing clearance. Check the condition of the oil pump and relief valve. If necessary, make regenerative repair of the pump.

Excessive crankshaft end play. Replace the crankshaft bearings.

There was a roundness of the crankshaft journals. Inst neck and replace the bearings (to repair size with belittling).

Disrupted oil supply. Add oil to the crankcase, bringing its level to the desired value.

On the problem of radical bearings indicates heavy but dull knock when the engine is under load. With the weakening of fixture handwheel deaf or dumb knock occurs during engine shutdown. It is usually accompanied by vibration. Axial play can be checked by moving crankshaft by the lever back first and then forward to the absolute amount of displacement metering. If the oil pressure is normal, remove the crankshaft bearing caps and make a measurement of backlashes in the past with the help of the calibrated plastic wire (set Plastigage). By the crankshaft journals for any ovality or other signs of deterioration can be performed only by means of a micrometer after removing the shaft.

Excessive consumption of motor oil

There have been leaks. Check the condition of the gaskets and seals. If necessary, replace.

Damaged or worn valve stem seals the valve stem. Replace defective caps.

Excessive landing clearance in the valve stem guide bushings. Replace the rails and / or caps.

Worn or broken piston rings. Replace rings on all pistons. Piston rings too tightly planted or stuck in their grooves. Replace the rings, clean the grooves.

Excessively worn cylinders, pistons and piston rings. Inst and / or othoninguyte cylinders, replace the pistons and / or piston rings.

Incorrectly installed compression rings, broken or jammed valve stem ring. Make replacement.

Before starting the engine to check for signs of oil leakage, it should be thoroughly cleaned and degreased. Warm up the engine to normal operating temperature. Enclose the ground directly under the engine clean (preferably white) piece of cardboard to identify the sources of leaks of oil. With valve stem seals damaged valve stem oil starts squeezed bypass valves in the combustion chamber. To test, run the engine for a while at idle speed, then suddenly open the throttle. If there is an oil leak in the bypass valve, the exhaust outlet pipe happen emission of dense smoke blue. Problems with pistons, piston rings and cylinders are usually accompanied by a loss of compression pressure measurement which should be done only by means of compression tester.

Motor oil pressure dropped

Fell the oil level in the sump. Check, if necessary add.

Fueled too liquid oil or its dilution occurred. Change oil and eliminate the cause of thinning, if any.

Reducing valve jammed or broken his spring. Remove the cause of jamming or replace a broken valve spring.

Excessive clearance in the bearings. Replace the pads, or (if necessary) pierce the crankshaft journal.

Excessive wear of the components of the oil pump. Carry out refurbishment or replace the pump.

If the vehicle is not equipped with a pressure gauge oil, remove the gauge, oil pressure switch and replace the gauge in its place. Measure the oil pressure as in the cold and the hot engine. When a faulty oil pump or pressure relief valve will be low in both cases. however, if there is a defect of the bearing, the oil pressure in a cold engine will be high, whereas after heating noticeably drops.

The engine does not rotate

Conjuring starter. Remove the starter. Check the condition and (if necessary) replace the damaged drive and / or flywheel.

Engine wedge while overheating. Remove the engine and disassemble it. Check the condition of the internal components, make the necessary replacement.

The cylinder is wet due to water being sucked into the air intake tract (eg, during the river crossing) .Vyvernite spark plug and dry cylinders.

Water enters the cylinder through the cylinder head gasket or cracks in the body of head / block. Remove the cylinder head. If the coolant leaks through the gasket, check the flatness of the mating surfaces of the head and block. If necessary, make a groove. At detection of cracks a head / unit should be replaced.

There is damage to the crankshaft or connecting rod and piston component groups. Remove and disassemble the engine. Inspect components, make necessary repairs / replacement.

Violating the integrity of the valve plate due to overheating or deformation fatigue. Remove the cylinder head and check the status of its components. Carry out the necessary refurbishment or replacement.

Frequent jamming the starter motor to the flywheel can be caused by bending or damage armature shaft drive gear teeth and / or flywheel. Condition of the flywheel can be checked through the mounting hole after removal of the last starter. If water got into the cylinders at once, in the process of crossing the water or any other similar reason, the deformation of the rods can occur. However, if the pure water hit the stopped engine, run it can be produced without any complications.

Remove the spark plug and unplug the system, as described in the section on checking compression pressure (engine setting) in Chapter Settings and maintenance.

Turn the engine by hand, pushing him out of the water as much as possible.

Then, turn the engine a starter - try not to lean over the engine block, as the water may be pushed through the spark plug hole with a decent pressure. Check engine oil distributor, carburetor, air cleaner, fuel filter and the fuel tank for signs of the presence of moisture. If moisture is detected, dry and replace the spark plug and start the engine.

When engine seizure due to overheating as a result of the fall of the coolant level clearly fail bearings, pistons, etc. components. Although sometimes the motor and can be successfully run and after ostuzhennym replace oil and coolant, typically such deviations occur soon as the increased oil flow, oil pressure, the noise level increases during engine operation, and the like, depending on the degree and nature damage.

When percolation coolant through the cylinder head gasket, or, if the compression pressure in the two adjacent cylinders is low, it is extremely important to carefully check the mating surfaces of the block and the cylinder head on the flatness. Through leaky gasket or crack in the head / block the cylinders can leak sufficient to engine failure from the rotation amount of water. Typically, this situation is accompanied by difficulty in starting, misfire, the release of steam from the exhaust pipe, as well as the fall of the coolant level.

Gas leak in the cooling system can be determined by removing the radiator cap and observation of bubbles in the upper tank of the radiator when the engine is running with turns of fast idling or without removing the radiator cap on excessive prelivu from the expansion tank.