Maintenance and assembly of fuel injection pumps and governors for truck cranes

1. Preparations before assembly

(1) Ensure a highly clean working environment. Workbenches, components, and tools used must all be thoroughly cleaned.

(2) After the components to be installed have been cleaned and inspected as qualified, they should be neatly arranged on the workbench, ensuring an orderly arrangement and being mixed but not chaotic.

2 Precautions for assembling fuel injection pumps

(1) The assembly process must use open-end wrenches, box wrenches, socket wrenches, screwdrivers, wood chips and all kinds of special tools. General-purpose tools such as adjustable wrenches and pipe wrenches are not allowed.

When assembling the camshaft, attention should be paid to its installation direction. After the fastening bolts of the camshaft intermediate bearing are evenly tightened, the camshaft should rotate smoothly, and its axial clearance should be 0.02-0.06mm. Note that the oil seal must not be installed in the wrong direction.

(3) The assembly sequence of the plunger assembly is opposite to the procedure during disassembly. When installing the plunger sleeve into the flange sleeve, it is necessary to ensure that the positioning grooves on the plunger sleeve are aligned with the positioning pin holes. After the pin is pressed in, the plunger sleeve should be able to move up and down slightly by 1-2. When installing O-rings, a small amount of lubricating oil should be applied to prevent damage and facilitate installation.

When installing the flow guide ring, pay attention to the difference between the top and bottom to avoid installing it wrongly. In addition, when installing, use a caliper to secure the caliper firmly.

When installing the oil outlet valve pair, it is necessary to keep the upper end face of the plunger sleeve and the lower end face of the oil outlet valve seat highly clean to ensure a tight mating surface and prevent oil leakage during the operation of the plunger, which may affect the uniformity of oil supply to each cylinder. The tightening torque of the oil outlet valve clamping seat is 107.8 N·m, and the tightening purpose is achieved in three stages: tight, loose, and tight.

After the plunger control sleeve is installed, it is necessary to ensure that the steel balls are fully inserted into the ball groove of the fuel supply control rod. After installation, the left and right movement of the fuel supply control rod can be checked manually to see if it is smooth.

(5) When installing the plunger into the plunger sleeve, it is particularly important to ensure that the marked side of the plunger flange block faces the direction of the locating pin. Do not install it in the wrong position; otherwise, the fuel injection pump will not work after installation. After the plunger is inserted into the plunger sleeve, the fuel supply control rod should also be pulled left and right to check if it is blocked.

3 Precautions for assembling the speed controller

(1) When installing the sliding sleeve and bushing, first accurately press the ball bearing into the bushing, and then press it into the sliding sleeve. After fixing the sliding sleeve, it is necessary to check whether the rotation of the bushing is smooth.

(2) When installing the flying block, the round nut used for fixing it should be tightened with a torque of 58.5N·m.

3) The gear rod travel adjustment bolt can be temporarily installed for use during commissioning.

(4) When the governor is installed into the pump body, its mating surface should be coated with adhesive to prevent oil leakage.

(5) As this governor is a dual-purpose governor with an additional control arm for speed control, the adjusting bolts on it should not be loosened at will before debugging.

4 Fault example

There was a truck crane. After the fuel injection pump was repaired and debugged, the following fault occurred during the reinstallation and test run: when the accelerator was released at medium speed of the engine, not only did the speed not decrease, but it also became faster and faster, showing signs of "runaway". After disassembling the fuel injection pump, it was found that when the plunger was installed into the sleeve, its position was misaligned by 180°, resulting in the opposite directions of fuel supply and fuel cut-off. When the throttle is released, the fuel supply control lever moves in the direction of reducing fuel supply, while the plunger moves in the direction of increasing fuel supply, causing the fuel injection pump to fail to work. After rotating the plunger by 180° and installing the machine for another test, everything was normal.