The technical condition of the engine is determined by fuel consumption, engine power, oil pressure, compression in the cylinders, engine noise and exhaust smoke
Measure the reference fuel consumption with the car (after driving at least 9,000 km) moving in top gear with a full load on a dry, even asphalt or concrete road at a speed of 90 km/h.
The front axle must be disengaged.
Perform the measurement on a section of the road 3–5 km long in two opposite directions.
Before driving, warm up the engine and chassis units with a vehicle mileage of 10–15 km.
To measure fuel consumption, you can use the tank model 361 GARO.
In winter, the reference fuel consumption may increase by no more than 10%.
The power qualities of the engine are determined by acceleration and the highest speed of the car.
The technical condition of the chassis units determine the length of the free run-out path of the vehicle.
On a flat stretch of paved highway, while driving at a steady speed of 50 km/h, disengage the gear and let the car drive smoothly until it comes to a complete stop.
Measure the free “run-out” path when driving in two opposite directions.
Check the control fuel consumption and the “run-out” of the car during normal, according to external signs, engine operation.
Before that, check and, if necessary, adjust the tire pressure, toe-in of the front wheels, and the completeness of the brake release.
Tire tread wear should be no more than 50%. The chassis is in good condition if the car (after a run of 9000 km) will move to a complete stop for at least 400 m.
Oil consumption during engine operation does not remain constant: during the break-in process, it decreases and after a run of 5,000–7,000 km it becomes equal to 70–150 g per 100 km of run.
Oil consumption increases after 70,000–90,000 km. If the oil consumption exceeds 450 g per 100 km, then the engine needs to be repaired.
Measuring oil consumption by topping up.
Check the oil pressure in the lubrication system with a control pressure gauge with a division value of not more than 49 kPa (0.5 kgf / cm 2), which is connected using a flexible hose instead of an oil pressure sensor.
To measure the oil pressure with the vehicle stationary, raise the rear axle on stands, disengage the front axle, start the engine and, engaging direct gear, manually open the carburetor throttle until the speedometer shows a speed of 45 km / h, and measure the pressure in the system.
Fig. 1. Checking compression in engine cylinders
Compression in the cylinders check on a warm engine with a model 179 GARO compression gauge.
To do this, unscrew the spark plugs, insert the rubber cone tip of the compression gauge into the spark plug hole (Fig. 1) and turn the crankshaft with the starter at full throttle and the carburetor without fuel.
The pressure in the cylinders must be at least 660 kPa (6.65 kgf/cm 3). The pressure difference in the cylinders must not exceed 98 kPa (1 kgf/cm 2).
Evenly low compression in all cylinders indicates, as a rule, significant wear of the cylinders and piston rings.
Decrease in compression in individual cylinders can occur as a result of "hanging" or burning valves, burning or breaking of piston rings, damage to the cylinder head gasket, or improper adjustment of valve clearances.
If, when pouring 25–30 cm 3 of clean oil into an engine cylinder with reduced compression, the pressure in it increases, this indicates a broken piston rings or their coking in the piston grooves.
If, however, the compression does not increase, then the cause of the malfunction must be sought in leaks, hanging and burning of the valves or in damage to the cylinder head gasket.
Lower compression in two adjacent cylinders indicates damage to the cylinder head gasket.
Fig. 2. Engine listening zones: 1 - distribution gears; 2 - valves; 3 - piston fingers; 4, 5 - pushers, valve stems, camshaft bearings; 6 - bearings of the main crankshaft
Engine knocks and noises listen with a stethoscope model K-69M GARO on a warm engine at different crankshaft speeds (Fig. 2).
Start listening with the distribution mechanism at low and medium crankshaft speeds: valves at 550–1000 min -1, tappets at 1000–1500 min -1 , distribution gears at 1000–2000 min -1.
Valve knocks are clearly audible from the side of the head, above the valve locations;
- - knocks of pushers and camshaft journals - from the side of the distribution mechanism, at the level of the camshaft axis;
- - knocks of timing gears - from the side of the cover.
Listen to the crank mechanism (pistons and main bearings) with a sharp change in engine speed within 500–2500 min -1.
To determine the cylinder in which there are knocks of the crank mechanism, remove the wires from the candles one by one.
The most clear bearing knocks are heard on the walls of the crankcase on the right side at the level of the camshaft:
- - knocks of pistons and piston pins - on the walls of the cooling jacket against the corresponding cylinders.
- - The knocks of the main bearings are dull, and the knocks of the connecting rod bearings and piston pins are sharper and more sonorous.
- - Piston knocks - sharp, rattling. They can be heard in all engine operating modes.
Knocks of pistons, piston pins, main and connecting rod bearings, valves and tappets on a warm engine indicate an engine malfunction.
Increased tapping of valves and tappets, merging into general engine noise with an increase in crankshaft speed, or periodic valve knocking that appears and disappears with a sharp change in crankshaft speed, as well as a slight knock of pistons on a cold engine, are not signs of engine malfunction .
We can also allow a slight high-pitched noise from the timing gears and oil pump gears.
Fig. 3. Engine suspension: 1 - protective cap; 2 - washer; 3 - top pillow; 4 - nest; 5 - bottom cushion; 6 - spacer sleeve; 7 - washer; 8 - bolt
The engine is mounted on the frame at four points (Fig. 3).
Periodically check the tightness of the nuts of the front and rear engine mounts.