The method for adjusting fuel supply timing is as follows: Open the inspection window on the side of the fuel injection pump and locate the tappet corresponding to the plunger to be adjusted. Loosen the timing screw locknut on the tappet. If the timing is late, back out the timing screw slightly, tighten it with the locknut, and try again. If the timing is advanced, back in the timing screw slightly, tighten it with the locknut, and try again (this situation is rare). After each adjustment, carefully rotate the cam slowly until the plunger reaches its highest point. Then, use a screwdriver to pry up the tail of the plunger and use a feeler gauge to measure the gap between the tail of the plunger and the head of the timing screw. This gap must be no less than 0.4mm to prevent the plunger from hitting the oil outlet valve seat and damaging both sets of components. If the timing requirements can only be met with a gap less than 0.4mm, the plunger must be replaced with a new one.
Fuel Advancer Maintenance
Just like ignition advance in gasoline engines, diesel engines also require the start of fuel injection before the piston reaches top dead center (TDC) on the compression stroke. This is called the injection advance angle. This advance angle ensures fuel atomization and combustion for maximum power. The crankshaft angle of the injection pump from the start of fuel injection to TDC is called the fuel advance angle. The fuel advance angle is indicated by a scaled line and an indicator on the advancer housing at the front of the injection pump.
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Common advancer failures include oil seal leakage and driven disc wear. The advancer's components operate in oil, which dampens the vibration of the flyweights. Oil deficiency can affect advancer performance. Wear on the driven disc's curved shape can also alter advancer performance. Therefore, when a diesel engine experiences insufficient power at high speed, thick smoke, or overheating, it's important to check the advancer's characteristics.
The advancer's operating characteristics should be checked on an injection pump test bench. For advancers used in non-supercharged CA6110 engines, the advance angle is 0° at speeds below 500 rpm and 6.5° at 1500 rpm. For advancers used in supercharged engines, the advance angle is 0° at speeds below 500 rpm and 5° at 1300 rpm. The advance angle changes linearly with speed, directly proportional to the speed. If the characteristic curve measured during testing deviates from the above requirements, the system should be repaired.
A change in the advancer's operating characteristics indicates wear on the contact surface between the driven plate and the flywheel roller. Remove the plate and reshape the curved surface with an oilstone to restore it to its original shape. Place a shim under the driven plate's spring seat with a thickness equal to the total wear and reshaping to maintain the curved surface's position. The repaired advancer should be reinstalled and retested until the operating characteristics meet the requirements. A leaking advancer can usually be corrected by simply replacing the oil seal.
Adjusting Unit Pump Injection Timing: Like separate pumps, unit pump injection timing significantly impacts diesel engine operation. Adjusting unit pump injection timing also involves adjusting the injection pump's fuel advance angle. Excessively large injection advance angles lower the cylinder air temperature, resulting in poor mixture formation upon fuel injection and a prolonged ignition delay, potentially leading to rough engine operation, poor idling, and starting difficulties. Excessively small injection advance angles delay combustion of the combustible mixture in the cylinder, lowering the maximum explosion pressure and temperature, and even incomplete combustion. This can lead to reduced engine power, overheating, black exhaust smoke, and reduced fuel economy. Therefore, adjusting unit pump fuel timing is crucial. Unlike separate pumps, unit pumps do not have a fuel advancer. Instead, adjustment is performed directly on the unit pump by varying the distance between the injection pump plunger and the injection pump tappet. The thickness of the adjustment shim Z is Ts. A thicker shim increases the fuel advance angle; a thinner shim decreases the fuel advance angle. It is necessary to adjust the appropriate thickness Ts of the adjusting gasket so that the injection pump fuel supply advance angle just meets the needs of the diesel engine.
1. Calculation of the thickness of the adjustment gasket Z
2. Calculation formula for the thickness of the adjustment gasket (1)
Ts=(L-Vh)-(Lo+A/100) Where: L - the height from the installation plane of the injection pump in the cylinder block to the surface of the injection pump tappet. The standard hole on the standard cylinder block is Le=150mm. After replacing the cylinder block, the height from the installation plane in the cylinder block to the tappet changes to L=Le+X+Y, where X+Y is the height difference after the change. Vh - the pre-stroke of the injection pump plunger from the bottom dead center to the moment of starting to pump oil. The Vh value can be found in the data table of the diesel engine model. For example, when the injection advance angle of the BF6M1013EC engine is 9°, the pre-stroke Vh value is 5.50mm.
L0 - the standard length from the installation plane of the single pump (when it is about to supply oil) in the cylinder pump to the surface of the single pump tappet, L0=143mm.
A/100-The difference between the standard length L0 of the single pump and the actual length. The A value is measured and marked on the pump body when the single pump leaves the factory.
When the theoretical value is calculated after replacing the cylinder body and the single pump, it can be rounded to the applicable adjustment gasket thickness value. For example, if the calculated value Ts is 1.665mm, the rounded gasket thickness Ss value is 1.7mm.
Calculation of replacing only the injection pump Z
Adjustment gasket thickness calculation formula (2)
Ts = Ek-(L0+A/100) Where: EK value can be found in the data table of the diesel engine model. The EP value is marked on the nameplate of the diesel engine. The EK value can be found from the Ep value to calculate the Ts value.
Adjustment of the fuel supply of the single pump
The fuel supply of the single pump is guaranteed by the original position of the fuel supply rack and the stroke of the rack. After the injection timing of each injection pump is adjusted, it is very important to ensure the position of the fuel supply rack.
The fuel rack adjustment diagram for the BF6M1013EC diesel engine is shown below.
X represents the fuel rack's position when it is in the stop position (X = 0.3-1.3 mm). This value is measured at the end of the housing. If it is too small, the fuel rack will not fully stop the fuel flow.
Y represents the maximum stroke of the fuel rack (Y = 16.8-17.1 mm). This rack stroke ensures maximum fuel delivery from the injection pump. A smaller Y value will affect fuel delivery and prevent full power at full throttle.
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