Bosch 110 series common rail injector

Bosch 110 series CRI2 Injector parts detail and measurement

Through the picture, you can clearly understand all the internal parts of the Bosch 110 injector and the relative positions of the high and low pressure oil lines (note: the red color in the figure is high pressure, and the yellow color is low pressure). When the solenoid valve is attracted, the armature plate starts to lift under the action of electromagnetic force, and at the same time, the spring force on the valve ball seat and the intermediate ball is reduced. Under the double action of oil pressure and electromagnetic force, the valve ball is lifted and the oil return channel opens. At this time, the high-pressure fuel at the oil nozzle end is higher than the fuel pressure at the top of the valve cap, and the oil needle is lifted up. At the same time, the injection hole is opened, and the high-pressure atomized fuel is injected into the engine combustion chamber to start work.

CRI2 belongs to Bosch 110 series, most of them are matched with small and medium-sized vehicles, and the maximum opening pressure is 1400bar. Bosch CRI2 injectors do not have separate solenoid valve pressure nuts. The tight position is integrated with the solenoid valve, and the disassembly and assembly are easier. CRI2 Bosch fuel injectors are different in size and length, and the solenoid valve wiring is also different. Except the obvious difference in shape and structure,  the internal structure and the adjustment methods of each stroke are very similar.

Below we will start to explain in detail each component and measurement method of Bosch 110 series injectors

Bosch injector solenoid F00RC30319

1 We already know about the 110 series solenoid valve. The loose position is integrated with the solenoid valve which is outer hexagon (Note: use S29D11 and S30D12 tools for disassembly), the recommended tightening torque is 25N.m.

There is an obvious part number on the top of the solenoid valve (for example: 0445110xxx),  which can check the corresponding valve assembly and nozzle through it. In the top oil return hole, there is an obvious dead position of the card slot mirror to prevent the oil return connector from falling off. The bottom of the solenoid valve has a leak-proof rubber ring to prevent fuel leakage inside the solenoid valve.

Pay attention to when checking the installation:
1 If the wiring connection of the solenoid valve is broken or damaged, it should be replaced in time. In order to prevent the solenoid valve from working poorly in the energized state, causing damage to the fuel injector, engine power and other problems.
2 If the hole on the top of the solenoid valve is bumped or damaged, it should be dealt with in time, to prevent the leakage of oil from here.
3 If the rubber ring at the bottom of the solenoid valve is damaged, it should be replaced in time to prevent fuel leakage inside the solenoid valve.

2 Solenoid valve spring (valve spring) spring height 115mm, spring outer diameter 5.1mm, inner diameter 2.3mm, a total of 8 turns (from the tangent at both ends), turn diameter 1.1mm (Note: Bosch CR12 and CRINI CRIN2 solenoid valve springs are not universal ). The solenoid valve spring is assembled inside the center hole of the solenoid valve. When the solenoid valve breaks the electromagnetic field and disappears, the solenoid valve spring expands its spring force and acts on the solenoid valve core, so that the solenoid valve core and the armature plate will quickly and accurately  take valve ball and to ball seat on the oil return hole of the valve cap, ensuring the requirements of the oil return amount and the oil injection amount.
The solenoid valve spring has a corresponding spring force. If you want to change this force, you can adjust it through the adjustment shims below it. The effect of this spring force on the oil quantity at medium speed is more obvious, and it will also affect the corresponding speed of the solenoid valve core and the armature disc under different pulse width control (adjustment is generally not recommended).
Pay attention to when checking the installation:
1 If there is any rust on the surface of the spring, it should be treated in time to prevent the spring from being inflexible and inaccurate when the solenoid valve is energized.
2 If the spring is bent, it should be replaced in time. It is also to prevent the spring response from being inflexible and inaccurate when the solenoid valve is powered on or off.
Bosch injector solenoid F00RC30319
Bosch solenoid spring gasket

3 The solenoid spring gasket sits at the bottom of the solenoid bore in contact with the top of the solenoid spring. solenoid bomb
The thickness of the solenoid valve spring gasket directly affects the size of the solenoid valve spring force (the size of the specification is strictly divided), which also plays a key role in the corresponding rate of the solenoid valve core and valve plate in the power on and off (Note: Bosch CR12 and CRIN1 CRIN2 are not common).
When inspecting the installation, note that.
1 solenoid valve spring gasket outer edge if there are scratches and rust stains should be dealt with in time to prevent the seat to the solenoid valve bore on the position of the change caused by the amount of injection and oil return irregularity.
2 Solenoid valve spring gasket and spring contact surface if there is a scratch should be dealt with in time to prevent the thickness change caused by the scratch.

4 The protective cover, also known as the protective sleeve, is an internal part of the solenoid valve unique to the Bosch CR12 (110) series. Height 5.2mm, bottom center hole inner diameter 5.5mm, top center hole inner diameter 4.0mm for tower design high protection sleeve is seated on the spool top U-shaped locking tab outer diameter position.
When checking the installation, note that the protective cover should be replaced in time if there is any deformation. To prevent the U-Lock from suddenly disengaging from the spool groove during normal operation, causing injector damage.

Bosch 110 injector protective sleeve
Bosch U-shaped locking plate

5 U-shaped locking plate, 5.4 mm outside diameter and 3.1 mm inside diameter (Note: not compatible with Bosch CRIN1 solenoid core small clamps).


The U-shaped locking plate is mounted in the upper groove of the spool to block the force exerted by the spring on the solenoid valve plate after power failure. There are strict thickness requirements to ensure the position in which the armature pan runs has a significant effect on the total travel of the solenoid assembly.

When inspecting the installation, note that any rust on the surface of the U-lock should be treated in time. To prevent changes in thickness that can cause problems such as unstable injector operation.

6 The outer diameter of the locking screw of the valve assembly pressure cap is 16.8mm, the diameter of the inner circle is 11.3mm (the inner hole corresponds to two included angles), and the height is 6.5mm. (Note: The cap screw with the Bosch CRIN1 valve assembly can be used universally).

The bottom flat end of the locking screw is in close contact with the top end of the lower seat of the solenoid valve, the locking screw is mostly internal hexagonal design, there is a wide and narrow difference between the top and bottom planes, when assembled, the slightly wider side downward corresponds to the solenoid valve lower seat. (Note: Recommended torque 55 N.m)

Due to the large hole in the valve assembly pressure cap screw, if the distance between the spool and the ball seat is too large, then when the solenoid valve is energized the ball seat in the magnetic field and oil pressure, is sucked and to the bottom of the spool when the position will be greatly offset. Similarly, when the solenoid valve’s disconnected electromagnetic field becomes weaker, the distance between the ball and the bonnet will also become farther away, and it will be impossible to accurately seat the bonnet in the center of the oil return hole position. This is one of the major causes of early wear of the valve cap.

When inspecting the installation, note that.
1 Valve assembly pressure cap locking screw ends, if there are any impurities, should be handled or polished in time to prevent the locking position under the standard locking torque is not in place, resulting in a change in the travel position, the injector will not work properly.
2 Replace any damaged threads of coarse locking screws on valve assemblies in a timely manner. Also to prevent the locking position from falling out of place under standard locking torque, causing a change in stroke position, the injector not working properly or an increase in oil return.

Bosch Valve cap screws
solenoid spool

7 Solenoid spool height 25.5mm, spool stem top diameter 2.5mm, spool stem diameter 4.3mm, small clamp placement diameter 2.6mm, spool base diameter 7.9mm, spool bottom and ball seat combination placement diameter 3.5mm.


The solenoid valve spool is installed in the center hole of the solenoid valve seat, and sits on the top section of the ball seat, when the valve is energized under the action of magnetic field, the solenoid valve spool will make up and down reciprocating motion with precise stroke size to ensure the precise opening position of the ball and the corresponding rate of the solenoid valve.


When inspecting the installation, please note: the solenoid valve core and solenoid valve seat hole and the inner hole of the armature plate, if there is any scratch or rust on the contact surface, it should be treated in time. To prevent the valve spool in the seat hole running inflexible, resulting in two core and solenoid valve seat and armature plate inner hole of the sticking state, so that the down seat to the valve ball seat on the force increases, from the surface to reduce the life of the valve cap. At the same time, the corresponding rate of power-on and power-off will also change, resulting in the injector injection volume and return volume of irregular changes.

8 The height of the solenoid valve plate is 6.5mm, the diameter of the large end face of the armature disc is 18.4mm, the diameter of the small end face is 7.4mm, and the diameter of the small hole is 4.3mm (Note: it is a clearance fit with the armature core).

The solenoid valve plate, solenoid valve core and solenoid valve lower seat play a vital role in Bosch CR12 injector maintenance!
The inner hole of the solenoid valve plate and the solenoid valve core belong to a gap fit, and the appearance is completely different from Bosch CRIN1 and CRIN2, and belongs to the unique structure of CR12.

Pay attention to when checking the installation:
1 If the surface of the inner hole of the solenoid valve plate is scratched or rusted, it should be dealt with in time. In order to prevent the valve core from running inflexibly in the valve plate hole, the sticky state of the valve core and the valve plate is caused, and the force of seating on the valve ball seat is increased, thereby reducing the service life of the bonnet. At the same time, the corresponding rates of power-on and power-off will also change, resulting in irregular changes in the amount of fuel injected and returned by the fuel injector.
2 If there are impurities or scratches on the top of the solenoid valve plate, they should be dealt with in time. In order to prevent the stroke parameters from being accurately controlled during measurement, the service life of the fuel injector is shortened.

solenoid plate
Bosch 110 common rail injector armature spring

9 armature spring
(Also known as a cushion spring whose spring force is so small that we cannot now measure it with a tool). Height 9.2mm, outside diameter 9.4mm, a total of 6 turns (from the amount of tangent at both ends), turn diameter 0.8mm drop seat in the valve assembly locking screw inside and solenoid valve seat end contact, while the top and armature plate bottom small end contact, when the solenoid valve power failure, the solenoid valve spool and valve plate in the solenoid valve spring force with the ball and seat at the same time downward movement, when the ball and seat accurate to the cap small hole position, the valve plate will also have a certain amount of running space (and the spool between the flexible fit gap has a close relationship) considering that this running distance will give the ball and seat an additional force, to prevent this additional force to the cap wear and add this spring, in order to relieve the solenoid valve plate under the inertia of the force generated.
When checking the installation, it should be noted that the surface of the cushion spring should be replaced in time if there is any rust. To prevent sudden breakage during normal operation, causing the injector to fail to work

10 Solenoid valve spring seat height 8.4mm, spring seat large end face diameter 15.9mm, spring seat small end face diameter 7.3mm, inner hole diameter 4.3mm.
The solenoid seat falls on the armature travel adjustment pad and attaches to the top of the valve cap. The two small holes at the bottom are the oil return channel and the injector body internal oil return channel, the solenoid valve spool through the middle hole.
The bottom large end face of the solenoid spool is combined with the bottom large end face of the solenoid spring seat, and the top is locked by the valve assembly pressure cap.
When inspecting the installation, note that:
1 Any impurities or scratches on the bottom surface of the solenoid seat should be dealt with in time to prevent changes in the bonding gap between the seat and the top of the bonnet, resulting in an inability to accurately control the amount of oil returned.
2 The two small holes in the bottom of the solenoid seat should be dealt with in time if they are blocked. To prevent the oil return channel from not opening smoothly, causing the solenoid valve to work poorly.
3 Any impurities or scratches in the center hole of the solenoid seat should be dealt with in a timely manner. To prevent the solenoid valve core from being inflexible when in motion, causing the solenoid valve to work poorly and the injector to not work properly.

Solenoid valve spring seat
Bosch 110 injector protective sleeve

11 Ball diameter 1.5mm (Note: Ball is made of ceramic!) (Theoretically zero wear, Bosch CRIN1 and CRIN2 are not universal). Ball seat height 2.1m, diameter 2.6mm. (Note: Bosch CRIN1 and CRIN2 are not universal).
The bonnet and ball are mounted in the small hole in the top of the bonnet (oil return hole). When the solenoid valve is energized, the armature in the electromagnetic force and oil pressure of the double action of the ball will be lifted, at this time the oil return channel open. It enters the oil return channel through a small hole in the body and enters the oil tank through the oil return line. After the solenoid valve power failure, the solenoid valve spool and valve plate under the action of the solenoid valve spring force, and at the same time the valve seat and ball at the corresponding rate down the seat to the valve cap oil return hole position, the oil return channel is closed.
We can see from the working principle that if the diameter and height of the ball and seat change, it will affect the rate at the time of seating and will change the amount of oil return. It will also cause early wear on the top end face of the bonnet, reducing the service life of the valve assembly, which can of course be eliminated by adjusting the corresponding gasket to achieve the best working condition and longest service life.
When inspecting the installation, note that.
1. The valve ball should be replaced in time if it wears out to prevent the return of oil from increasing, causing the injectors to work poorly and the engine speed limit.
2. If the valve ball seat is broken or worn, it should be replaced in time to prevent the oil return volume from increasing, resulting in poor working of the injectors and engine speed limit.

12 The Air gap adjustment shims has an outer diameter of 28.6mm and an inner diameter of 18.9mm, and the thickness has strict dimensional requirements.
The Air gap adjustment shims gasket sits where the inner end face of the injector meets the bottom end face of the solenoid.
The key component that controls the distance between the internal end face of the solenoid valve and where it meets when the plate of the solenoid valve moves upward under the force of the cushion spring.
When inspecting the installation, note that.
1 Air gap adjustment shims should be replaced in time for any deformation. To prevent changes in the distance of the solenoid valve plate in motion after power failure, resulting in changes in the amount of oil injection and oil return.
2 Air gap adjustment shims surface should be treated in time if there is any rust. To prevent changes in the stroke position, resulting in changes in the corresponding rate of the solenoid valve and solenoid valve plate.

Air gap adjustment shims
Bosch 110 injector protective sleeve

13

Valve sets(also known as control plunger) are composed of a valve rod and a cap. Due to compatibility with various models, the classification of valve types is detailed. At the top of the valve cap, there is a small through-hole (also known as the return oil hole), and there is also a small hole on the side (this small hole is also known as the Z hole or high-pressure inlet hole). The top hole is connected to the return oil chamber, and the Z hole is connected to the high-pressure chamber. As the solenoid valve operates, the fuel pressure in the high-pressure chamber and the low-pressure chamber changes. The high-pressure fuel passes through the high-pressure chamber channel and enters the nozzle inlet hole, lifting the nozzle needle valve while overcoming the spring force. The high-pressure fuel enters the engine combustion chamber through the nozzle spray hole, enabling the engine to operate.

Based on its working principle, we can assume that the valve stem primarily works in an up and down reciprocating motion within the body. The Z hole position (high-pressure inlet hole) of the valve cap forms a high-pressure reservoir at the bottom of the valve cap (the position varies depending on different valve caps in the production process), which stores high-pressure fuel. Therefore, during maintenance, if the valve cap is replaced separately, the corresponding stroke size (needle valve stroke) must be measured. The valve components have strict requirements for lift in each operating condition, which can be achieved by adjusting the thickness of various gaskets (the thickness of the CRI2 adjustment gasket plays a key role in the displacement position of the valve component). It is also closely related to the preset force of the spring and the corresponding rate of the solenoid valve.

When inspecting and installing, the following points should be noted:

  1. If there is wear on the working surface of the valve stem, it should be replaced promptly. Grinding the valve stem to fit the valve cap is not recommended to prevent an increase in the return oil volume, which can cause delayed establishment of rail pressure, resulting in difficult vehicle starting and decreased power.
  2. If there is wear on the top surface of the valve cap’s return oil cavity, it should be replaced promptly to prevent inadequate sealing of the valve ball during seating, which can cause an increase in the return oil volume and result in delayed establishment of rail pressure, difficult vehicle starting, and decreased power.
  3. If there is rust on the surface of the valve stem, it should be replaced promptly to prevent the valve stem from being inflexible during normal operation of the injector, causing different stability in high and low-pressure fuel pressures and causing the injector to be delayed in closing or open state.
  4. If the Z hole of the valve cap is blocked or contains impurities, it should be replaced promptly to prevent the high-pressure fuel from flowing smoothly, resulting in the injector not spraying fuel and the rail pressure unable to establish normally, leading to difficult vehicle starting.