Created on:2021-06-28 11:48

Tractor hydraulic failure -- feed pump and main pump failure

Tractor hydraulic failure -- feed pump and main pump failure

There are two hydraulic pumps in the hydraulic system of a John Deere load shifting tractor, namely the feed pump and the main pump.

(1) Feed pump

The feed pump is also called clutch pump or transmission pump. The oil is supplied by medium pressure 1.23 ~ 1.37mpa. It is a separated internal gear pump, which is installed at the front end of the clutch set in the transmission device and driven by the drive shaft of the clutch set.

① Test of feed pump

a. Remove the pedal in the cab, remove the plug from the right corner of the clutch housing on the right side of the oil return pipeline, and connect the pressure gauge of 0 ~ 0.5MPa. The test results show that when the engine speed is 1500r / min, the oil temperature is 43 ℃, the pressure should be 0.11mpa, and the oil temperature is 66 ℃, the pressure should be 0.08mpa; The pressure should be 0.2MPa when the engine speed is 2000r / min, the oil temperature is 43 ℃ and 0.16mpa when the oil temperature is 66 ℃.

b. Open the control valve of the maintenance accessory flow meter on John Deere tractor, put the metering button of the selection control valve on the lower right side at the "maximum flow" position, and put the metering button of the selection control valve on the left side at the minimum flow position.

c. Put the handle of each hydraulic control system in the cab in the "neutral" position, and adjust the engine to 1000r / min. Rotate the control valve of the flowmeter until the pointer of the pressure gauge swings and does not rise. At this time, the pressure should be 0.89 ~ 0.95mpa.

d. Move the handle of the left "selection control valve" in the cab back to leave the neutral position to make the pressure oil flow back to the oil tank and let the engine work at 2000r / min. adjust the metering button of the left "selection control valve" to make the lubricating oil pressure be 0.07MPa. At this time, the minimum flow at 43 ℃ should be 45.4l/min, When the oil temperature is 66 ℃, the minimum flow rate is 43.5 L / min.

② Fault and diagnosis of feed pump

a. When the handle or pedal moves from one position to another and the pressure change exceeds 0.02MPa, the oil supply filter is blocked; The bottom oil inlet filter screen is blocked; The inlet or outlet of the feed pump is blocked; The regulating pressure of the pressure regulating valve is not correct.

b. When the handle or pedal moves from one position to another and the flow rate changes more than 3.8l/min, the oil outlet pipe or O-ring leaks; Leakage of oil passage cover plate; Oil supply filter overflow valve leakage; Gasket leakage of pressure regulating valve assembly and clutch valve housing; The oil seal in the pump leaks.

(2) Main pump

The main pump of the hydraulic system is a radial piston variable displacement pump, which is installed in the front of the engine and driven by the power of the crankshaft with a special coupling.

There are eight plungers in one week of the main pump, all of which work in the same state. A 45 ml pump is used on tractors without front wheel drive and a 66 ml pump is used on tractors with front wheel drive. There is a stroke control valve in the front cover of the pump, which can automatically adjust the pump oil volume according to the load demand.

① Main pump assembly and adjustment requirements

a. After assembly, the axial clearance of the main pump shaft should be 0.02 ~ 0.08mm.

b. The bolt tightening torque of oil inlet valve is 133.28n · M.

C. the lift of oil inlet valve should be 1.52-2.03mm.

d. When assembling the oil inlet valve, the distance between the pipe and the machined surface of the pump body should be 13.54-13.64mm.

e. The distance between the oil drain valve nut and the pump is 3.2mm.

f. The tightening torque of plunger plug is 133.28n · M.

g. The tightening torque of the fixing and connecting bolts of the main pump is as follows: the connecting bolts of the pump and the pump bracket are 112.7n · m, the bolts of the connecting shaft are 46.06 n · m, the special driving bolts of the pump are 46.06 n · m, and the locking nut of the coupling is 40.18 n · M.

② Fault and diagnosis of main pump

a. Do not pump oil. The driving part of the pump shaft is damaged, the stroke cannot be closed, the stroke control valve is not adjusted correctly, there is a fault or the oil supply circuit leaks.

b. The pump oil volume is small“ No load "low pressure, stroke control valve, valve seat, spring or oil seal failure, plunger or pump chamber wear or damage, drain valve or spring damage, oil inlet valve leakage.

c. The suspension system is slow“ The "no-load" pressure is low, the stroke control valve, valve seat, spring or oil seal is faulty, the oil seal of the oil drain valve sleeve of the crankshaft chamber is damaged, and the oil drain valve of the crankshaft chamber is blocked in the closed position.

d. The pressure is too high. The oil filter sleeve of the crankcase drain valve is blocked.

The response of E. pump was slow. The crankcase drain valve is installed too low, and the crankcase drain valve is blocked in the closed position.

f. The suspension motion vibrates“ No load "low pressure, stroke control valve, valve seat, spring or oil seal failure, plunger sticking, drain valve or spring damage, oil inlet valve damage, insufficient oil inlet, pressure control valve failure.

g. The pump and pipe vibrate. The installation of oil drain valve in crankshaft chamber is too high, the oil drain valve or spring is damaged, the oil inlet valve leaks and the oil inlet valve is damaged.

h. The oil seal of pump shaft is damaged. The drain valve is damaged, the square oil seal is damaged, and the steering system motor leaks.

i. The pump makes a noise or squeal. The coupling is worn or partially detached, the "no-load" pressure is low, the stroke control valve, valve seat, spring or oil seal are faulty, the oil drain valve of crankshaft chamber is installed too high, the oil inlet valve leaks oil, the air seeps into the oil inlet pipe, and the oil inlet is insufficient.

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