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Yanmar 4TNV88-BXBVB engine fault diagnosis

1 determined using the stall detection engine failure

1.1 Determination stall

Stall determination is the use of the machine itself or hydraulic power transmission system of work load on the engine. Test torque for a particular engine speed is decreased by the maximum extent of idle speed, to evaluate the output of the engine. Carter and Komatsu are using this method to determine the engine is equipped with a host up engine performance.

1.2 Preparation before stall detection

(1) Check the stall performance, such as the monitor can not monitor the speed and the use of hand-held tachometer measurements, carried out by two people: one person to inspect the engine speed, the other people in the cab control operations. They are to act in harmony, in the test effectively throughout their personal and mechanical safety.

(2) the photoelectric tachometer tachometer sheeting used when observing through the flywheel holes Yanmar affixed to the outer periphery of the engine flywheel.

Reflectors affixed by the observation hole flywheel engine flywheel peripheral

Reflectors affixed by the observation hole flywheel engine flywheel peripheral

(3) Test conditions: engine water temperature 75-90 ℃, hydraulic oil temperature is 70-80 ℃.

(4) the radius of gyration excavator parked on a flat barrier.

1.3 detection step

(1) Start the engine, the throttle pulled maximum speed of the engine idling. If the measured high idle speed is 2510 ± 50r/min, you do not need to adjust the maximum speed limit device.

(2) Load: Individual manipulation excavator arm or arm to limit hydraulic cylinder piston position in the formation of the overflow.

(3) with the rotational speed of the engine overflow table to check speed, the hydraulic pressure reading is the stall speed of the measured values​​. Stall test each operation should be completed within ten seconds. When the stall time is greater than 20 seconds, should the operating lever back to the position quickly.

1.4 Reading determination

If the measured stall speed of 2050r/min, Yanmar  stall speed reference value 2200 ± 50r/min compared to determine the stall too large. Check the hydraulic system in the normal context, should be further diagnose the engine stall when smoked while no significant change in the power output is insufficient.

(2) the use of fault diagnosis Cheat

1.The engine intake system, exhaust valve clearance is not suitable.
Failure analysis is lack of engine power, exhaust color is “normal.”
2 Engine system compression pressure leak valve seat portion.
Failure analysis is lack of engine power, exhaust color is “normal”
3. Engine system piston rings, pistons, cylinder wear.
Failure analysis is lack of engine power, exhaust color is “white”
4. Engine fuel supply system is inadequate.
Failure analysis is lack of engine power, exhaust color is “white”
5 turbocharger contamination, failure analysis for the lack of engine power, exhaust color to “white” or “black”

3 engine output inadequate (exhaust smoke color normal) may have the following factors

Fuel pump fuel supply shortage may be due to leakage of the plunger, high pressure tubing deformation, delivery valve leaks, clogged injectors, poor atomization, oil return is too large, injection angle changed.

Low oil pressure low pressure system, fuel tank respirator may be due to clogged water separator clogged filter clogging, electronic pump and rotor pump leaks, constant pressure valve spring failure.

Regular oil changes, probably due to the cam and plunger injection pump wear adjustment screw loose.

Governor poor, probably due to coupling mechanism Songkuang, hammer bearing wear, loosening the adjusting screw out of control.

Fuel poor, probably because the fuel is mixed with water or impurities in the fuel grade is incorrect.

According to the survey concluded the aircraft stalled mainly due to “quantitative” enough to take in the field to adjust the total amount of oil fuel pump control screw (see figure below), first remove the adjustment screw sheath with a knife to change the adjustment screw reverse lap increase the amount of oil to the engine rpm required.

Adjusted gross oil chart



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