Difference between MUI and EUI in cylinder head

This picture shows the difference between the Mechanical Unit Injection (MUI)
and current Electronic Unit Injection (EUI) installation in the cylinder head.
Notice the Helper Spring on the injector pushrod. This arrangement is designed
to keep the follower in constant contact with the camshaft. The helper spring is
required due to the increased injection pressures of 151 MPa (22000 psi) and the
steeper, high lift camshaft lobe profile.
The 3500B has a larger diameter camshaft to accommodate the higher injection
pressures generated in the unit injector pumps.

DIRECT INJECTION UNIT INJECTOR FUEL SYSTEM - caterpillar fuel system

DIRECT INJECTION UNIT INJECTOR FUEL SYSTEM
The 3500 Series Engines use the direct injection combustion system. This system has the advantages of: low heat rejection (in comparison to pre-combustion); low fuel consumption; and easy starting.

UNIT INJECTOR AND CONTROL LINKAGE
A fuel injector (7) is in a central bore of each cylinder head. The position of the rack (6) of each injector is changed by a bellcrank and bracket (5) that is held to the top of the cylinder head by bolts. Each bellcrank
is moved by a control rod (4) connected to a hollow torsion shaft (1) through a lever (3).

Rotation of the torsion shaft (1) is done by the governor input shaft (10) and causes in and our movement of the rack (6).
The torsion shafts (1 and 8) are just below the camshafts of each bank of cylinders. A hollow cross shaft (9) at the front of the engine connects the right torsion shaft (1) and left torsion shaft (8) so they move together at the same time.

The control rods (4) have a “click” screw adjustment (11) at the bellcrank ends. There is one adjustment screw for each rack. This adjustment is used to synchronize all racks together. The adjustment sets the racks of the separate unit injectors so that they have the same reference position.
Also, there is a spring in the top end of the control rod. If one unit injector plunger will not turn (is STUCK) or the rack of that unit injector will not move, the control rod can still control the racks of the other injectors. This will prevent engine overspeed and the engine can be stopped. This design characteristic is for protection of the engine from damage.
Another protection for the engine: If the control linkage becomes disconnected from the governor, the WEIGHT of the control linkage can move the racks of the unit injectors to the fuel OFF position. The engine will STOP.
The torsion shafts (1 and 8) are marked with red and green colors on the inside diameter for assembly identification purposes. The left torsion shaft (8) has red and the right has green

In the inset we can see the power pad. The power pad has the power setting screw cover. The power setting screw cover has two bolts. The top bolt is the synchronizing pin and fastens the power setting screw cover. The bottom bolt also holds the cover on. With the cover removed, we can see the power setting screw and locknut.
The hole to the right of the power screw is where the collet and dial indicator is installed for measurement and adjustment of the power setting. The hole to the left of the power setting screw is for the synchronizing pin (the top bolt). This pin is used to put the fuel control linkage in the reference (fixed) position, when the synchronizing adjustment is made to the unit injectors.

NOTE: This illustration is not correct. The seal goes through the cover bolt, not the synchronizing pin.

In the highlighted area we see the power setting screw.
The power setting screw makes contact with the fuel stop lever. Adjustment of the power setting screw controls the maximum power setting of the engine. It controls the maximum movement of the control linkage and all injector racks.
Above the highlighted area is the governor lever which is connected to the governor output shaft. The governor lever, the fuel stop lever, the front end of the right torsion shaft and the power setting screw are in the front gear housing behind the power pad.

In this slide we see the fuel control linkage operation from the front of the engine. When the speed control of the governor is moved toward maximum rpm, the governor output shaft (black arrow) turns clockwise and moves the governor shaft lever to the left. A pin in the governor shaft lever is in the groove in the fuel stop lever and moves it to the left. The fuel stop lever turns the right torsion shaft counterclockwise as seen by the arrow. This counterclockwise movement moves the control rod up. This movement pivots the bellcrank and pulls the rack out of the injector in the fuel “ON” direction. The right and left torsion shafts always move together.
The ends of the shafts are connected to the ends of the cross shaft by a fork lever-ball lever arrangement (to understand better, see iron later).

This is the cross shaft on the front of the engine. It connects the right torsion shaft to the left torsion shaft.

The front housing is removed.

This shows the end of the right torsion shaft and cross shaft. You can also see the connection between the fork lever on the torsion shaft and ball lever on the cross shaft. This connection has a smalltolerance.
We can also see the fuel stop lever.

This shows the end of the torsion shaft and the left end of the cross shaft. The connection of the ball lever on the cross shaft with the fork lever on the torsion shaft can be seen.

The front housing is installed in this view.

Here we see inside the camshaft compartment. The camshaft is above. The torsion shaft of the fuel control linkage is below. The control rod of the torsion shaft (center) goes up to the bellcrank assembly of the unit injector.

This shows the rear end of the right torsion shaft. The support bracket for the shaft can be seen.

Also with the front housing removed, we can see the fuel stop lever clearly. With the front housing installed. . .

. . . we can see the power setting screw in contact with the fuel stop lever.
This also shows the notch in the fuel stop lever which connects with the pin of the governor lever.
We will learn about the power setting adjustment later; however, you can see how the power setting screw controls the position of the fuel stop lever by stopping its movement.

UNIT INJECTOR AND OPERATION
In this schematic we can see the injection components of this fuel system.
The components are:
1. injector cam lobe of engine camshaft;
2. a push rod
2a. a lifter assembly
3. an injector rocker arm
4. an injector clamp
5. a unit injector
6. a section of cylinder head; and
7. a piston in a cylinder

In this schematic we can see the control components of this fuel system.
The components are:
8. control lever on torsion shaft
9. control rod
10. bellcrank
11. injector rack
12. injector plunger

Here we see two unit injectors. The one on the left has been cut away for instructional purposes. The injector on the right is complete.
This slide shows the:
1. injector body
2. follower
3. follower return spring
4. rack
5. injector housing (nut); and the
6. injector nozzle (spray tip).

This is the unit injector designed and manufactured by Caterpillar. It is being used for current production marine engines. Remanufactured nozzles will be available. Service tools (to be announced at a later date) will permit some field service to be done on these nozzles. This injector has a removable cone on the end and a trim screw for bench calibration.

The injection of fuel is made by the rotation of the engine camshaft which causes the cam to lift the lifter assembly and push the rod up. When the push rod moves the injector rocker arm up, the contact of the rocker arm pushes the follower an injector plunger down. As the plunger moves down, fuel is injected into the combustion chamber. As the lower scroll on the plunger goes beyond the lower port, injection stops. When the rocker arm stops its downward movement, the follower return spring pushes the follower up with the plunger. The follower return spring also keeps a force on the rocker arm push rod and lifter. This force keeps the lifter in contact with the cam.

Looking at the cutaway of the injector, we can see the:
1. plunger
2. barrel
3. lower port
4. upper port; and the
5. spill deflector
The plunger position shown is at the top of the stroke.
The barrel (2) has an upper port (4) and a lower port (3). The relation of the scrolls to the ports:
(1) changes the length of the effective stoke and the quantity of fuel per injection stroke;

(2) permits the start of the effective stroke to be variable in relation to piston position.

The smaller the quantity (VOLUME) of fuel injected during the injection stroke, the later (NEARER TO TOP CENTER) injection takes place.

The larger the quantity (VOLUME) of fuel injected during the injection stroke, the earlier (FARTHER FROM TOP CENTER) injection takes place.
Movement of the control linkage and rack turns the plunger and changes the quantity of fuel injected and the point at which injection starts.
The action of the double scroll is a method of timing advance.
Older injectors are double scroll. Newer injectors aresingle scroll.

Let us look at the nozzle of the injector. We see the:
1. check valve
2. check valve cage
3. valve spring and seat
4. spring cage
5. needle valve
6. spray tip; and the
7. injector housing or nut
The spray tip has several small orifices. Each nozzle has two dowels in the body which puts it in the correct position when installed. This position puts the rack in the correct location with the bell crank and the spray tip at the correct angle with the surface of the piston.
The plunger position shown here is on the downward stroke and the lower port is just closed.

The plunger position shown here is the start of the injection stroke. Both the lower port and the upper port are closed. It is at the start of the effective stroke.
During the effective stroke, the plunger forces fuel into the nozzle of the injector. The fuel goes around the check valve and through passages in the check valve cage. After fuel goes through the valve spring cage, it goes into the passages in the spray tip. The passages sends the fuel to the chamber around the needle valve. Here the fuel pressure lifts the needle valve off the seat and fuel flows through the spray tip and out the orifices into the combustion chamber. Injection of fuel continues until the lower scroll on the plunger goes by the lower port, the pressure of the fuel against the needle valve is less.

The valve spring pushes the needle valve closed. This stops the flow of fuel into the combustion chamber. Also, when the fuel is released through the lower port, the fuel pressure above the check valve decreases. The fuel pressure in the tip chamber then pushes the check valve up against the end of the barrel. With the needle valve on the seat and the check valve against the end of the barrel, combustion gases cannot get into the injector and cause damage between injection strokes.

NOTE: If the needle valve is held open by foreign particles between injection cycles,
combustion gases can come into the injector and cause damage.

LUBRICATION SYSTEM - Caterpillar

LUBRICATION SYSTEMThe engine oil pressure has a normal operating range from 345 to 480 kPa (50 to 70 psi) and will be approximately 450 kPa (65 psi) at full load rpm. Flow of oil through the engine at rated rpm is approximately 340 litres/min (90 gpm).

In this diagram of the lubrication system, we see the oil reservoir (sump in the oil pan), the oil pump (1) with a pressure relief valve (2); the oil cooler (3) with a bypass valve (2); the oil line from the cooler to the oil filter base/housing (4); with bypass valve (2) [one bypass valve for each filter]. The oil goes from the oil filters through the oil line to the oil elbow (manifold) on the left top front of the block.

The oil pump takes oil from the sump and sends it through the oil cooler, oil filters, and into the oil elbow (manifold).

Oil is sent to the turbochargers through outside lines (9) that are connected to the elbow on the left from (if turbocharger is top mounted). Turbocharger drain lines empty into the camshaft compartments through the camshaft side covers (10).
In the elbow (manifold), the oil is divided; one branch is sent to a camshaft oil gallery (7) below the camshaft and fuel control shaft, the other branch to a main oil gallery (5) which is above the main bearings of the crankshaft and on the centerline of
the block.

The main oil gallery (5) sends oil through vertically drilled passages to each main bearing, then through the crankshaft to each connecting rod bearing.

The oil that flows to the rear of the main oil gallery is sent up to the rear top of the block into an adapter (elbow manifold). The adapter sends the oil again into a camshaft oil gallery (7) in the block to the passage below the right camshaft.
The adapter also has plugs that may be removed to supply oil when the turbochargers are mounted on the rear of the engine.

 

The inset on the right of the diagram shows the oil passages on the right side of the engine. The oil in camshaft oil gallery (7) on the left side and the right side below the camshafts sends oil to the camshaft journals (11). The oil goes through hollow dowels to the cylinder heads through passages to the three lifters (two lifters for
valves, one for the injector) and the rocker arm shaft (12).

Oil is sent from each end of the main oil gallery (5) through small passages to the sequence valves (6). The two sequence valves control oil flow into piston cooling jet manifolds. There is one sequence valve on the left front of the block for the left passage and one on the right rear of the block for the right passage.

The purpose of the valves is to stop oil flow into the piston cooling jet manifold until oil in passage (5) has more than 140 kPa (20 psi) pressure. During engine start-up, the sequence valves decrease the time needed for the oil pressure to come up in the
main oil gallery to the main and connecting rod bearings. The sequence valves also hold the oil pressure up during engine idling, especially when the oil is hot, and parts are worn.

When the oil pressure is more than 140 kPa (20 psi), the sequence valves open and let oil go to the lower small passages (8) alongside of the crankcase. This oil is sent to the piston cooling jets (one for each piston). Each cooling jet has two openings. As oil is forced through each opening, one stream (spray) of oil is sent to a passage in the bottom of the piston which takes the oil to a circular manifold inside the piston and cools the piston. The other stream of oil hits the piston underside to cool it
and give lubrication to the piston pin and bearing.

The inset on the right of the diagram shows the oil passage to the gear train. Oil is sent to the front and rear gear trains from the oil passages below the camshafts (7) through passages drilled in the front and rear housings and the front and rear
block face.

The oil pump (1) and pressure relief valve (2) can be seen here.

The oil pressure relief valve is in the oil pump body and keeps the oil at the correct pressure. It opens at above normal pressures and sends the extra oil back to the pump inlet. Oil pressure must be measured when the engine is at normal temperature of operation. Also, oil pressure must be measured at a location (tap) AFTER the oil
has gone through the oil cooler and filters. Oil pressure can be measured on each side of the block at the oil gallery plug.

Here we can see the:
1. oil cooler
2. oil line from the oil pump to the oil cooler
3. oil line to the filter base housing on the left side of the engine
The oil cooler (1) is on the right side of the engine and is a tube core-type. Coolant goes through tubes in the cooler, and oil goes around the outside of the tubes. The oil cooler supply line (2) is on the outside of the cooler. The oil flows through the supply line through the cooler to the oil line to the filter base housing (3). On the vehicle arrangement, the oil line goes under the oil pan to the filter base housing on the left side of the engine.

The oil cooler bypass valve is in the oil cooler housing. The oil cooler bypass valve permits oil to go around the cooler when the oil is cold and thick or when there is a restriction in the cooler. The bypass valve will open when there is a pressure
difference of 160 to 200 kPa (23 to 29 psi) across the oil cooler (from the inlet of the cooler to the outlet of the cooler).

This is the oil line (arrow) from the oil cooler to the filter base housing which goes under the oil pan. Also we can see the oil pan is held to the bottom of the block with bolts. The bolts go through the block and are turned into threaded holes in the pan. To improve service on some arrangements, the bolts go through the oil pan to the block.

VEHICLE FILTER ARRANGEMENT
On the left side of the engine, we see the three oil filters. The oil goes from the filter base housing to the manifold (elbow) on the front left top of the block. The oil flow
from the oil cooler goes through the line on the right into the filter base/housing and to the oil filters. (The oil filters shown are full-flow type spin-on filters.)

Each oil filter has a bypass valve behind the plates (see arrows). When the oil filters have a restriction, the bypass valve opens and sends the flow directly to the
oil line on the left which sends the oil to the block.
Each oil filter bypass valve will open when there is a pressure difference of 180 to 200 kPa (26 to 32 psi) across the filter (from the inlet side of the filter to the outlet side of the filter).

NOTE: Other applications of this engine can have the oil
filters at other locations.

Use a strap wrench , if needed, to remove the oil filters.

Change the oil filters when you change the engine oil at the service interval given in the Operation Guide.
Before installing the oil filters, be sure the old gasket is removed and the filter base is clean.
To install the oil filter, put clean oil on the gasket and turn the filter on the filter base until it contacts the base. Turn the filter 3/4 of one turn (270 degrees) more.

Put more oil in the engine when the oil level is at the ADD oil mark on the gauge.
Change the oil in the engine as recommended in the Lubrication and Maintenance Guide.
CAUTION
Vehicle engine dipsticks will be marked on both sides.
Be sure to read the correct side. The other side will read ADD, HOT-RUNNING.

The small lines going from the front, left oil manifold (elbow), sends oil to the turbochargers when they are top mounted. The large line from the bottom of the turbocharger is the oil drain which returns the oil to the camshaft compartment and
crankcase.

On the right rear of the engine block is the adapter (elbow manifold). Oil is sent from the main oil passage (gallery) to the top of the block. The adapter sends the oil into the camshaft bearing oil gallery. When the turbochargers are rear mounted, such as a Generator Set, Marine Engine, or Marine Auxiliary Engine, oil for the turbochargers comes from the two large plugs in the adapter.

OTHER ENGINES
Other engines (Industrial, Generator Sets, Marine and Marine Auxiliary Engine arrangements) have the oil filter housing (2) mounted across the front of
the engine.
Here we can see the:
1. drain valve
2. filter housing
3. bypass valve; and
The filter housing(2) has three (3) filter elements. The filter housing has a single bypass valve (3). On vehicular engines, there is one bypass valve for each filter. The oil inlet line goes from the oil cooler to the filter housing. The oil outlet line goes
from the oil filter housing to the oil manifold (elbow) on the block. Clean oil from the filters goes into the block in the same location as the vehicle engines.

The filter elements should be changed when the engine oil is changed. To install new filter elements,
open the drain valve (1) and drain the oil from the filter housing. Then remove the cap from the end (right-hand side) of the filter housing.
Remove the three filter elements and clean the filter housing with a clean lint-free shop towel.
Install new filter elements, a new seal, if needed.
Put the cap on the filter housing. After the engine is started, check the cap and seal for leaks.
A duplex oil filter is shown here.

Here we can see the crankcase dipstick on this industrial/generator set engine. There are either right-hand or left-hand locations for the dipstick
on the different engine arrangements.

Be sure there is oil in the sump before starting the engine. Then check the oil level with the engine idling and with the oil hot. The oil must be checked daily or every ten service meter units.
The oil must be between the “ADD” and “FULL” marks on the oil level dipstick.

Cooling System - Caterpillar

Cooling System


COOLING SYSTEM SCHEMATIC
This diagram shows the basic cooling system. We can use it to see the components of the system and see how they are connected. In the diagram, we see the engine block, cylinder heads (separate heads for each cylinder), coolant manifold, housing of the temperature regulators (thermostats), water outlets bypass line from regulator housing to water pump, water pump, water inlet from radiator or heat exchanger, coolant line to the aftercooler, and the oil cooler.
1. water pump
2. oil cooler
3. cylinder heads
4. water manifold (right side)
5. aftercooler
6. temperature regulator housing
7. bypass line from regulator housing to water pump.



COOLING SYSTEM FLOWCoolant flow comes from the elbow which is connected to the radiator or other heat exchanger into the center of the water pump. The cooler flow is divided at the outlet of the water pump. One partflows to the aftercooler; the other part to the oil cooler.
Coolant sent to the aftercooler goes through the aftercooler and is sent by an elbow into a passage in the block near the center of the vee at the rear of the block. The coolant sent to the oil cooler goes through the oil cooler and flows into the water jacket of the block at the right rear cylinder. The coolant mixes and goes to both
sides of the block through distribution manifolds connected to the water jack of all the cylinders.
The main distribution manifold is located just above the main bearing oil gallery.


COOLING SYSTEM FLOW
The coolant flows up through the water jackets and around the cylinder liners from the bottom to the top. Near the top of the cylinder liners, where the temperature is the hottest, the water jacket is made smaller. This shelf (smaller area) causes the coolant to flow faster for better liner cooling. Coolant from the top of the liners goes into the cylinder head which sends the coolant around the parts where the temperature is the hottest. Coolant then goes to the top of the cylinder head and out through an elbow, one at each cylinder head, into a manifold, one for each back of cylinders. Coolant goes through the manifold to the thermostat housing.



The water pump is gear driven at 1-1/3 times engine speed for the 1300 to 1800 rpm high speed engine and 2 times engine speed for the 1300 rpm low speed engines.

Coolant comes from the aftercooler and goes into this

elbow and into the engine block.

After the coolant goes through the oil cooler, it is sent into the engine block at the right rear cylinder. Coolant from the oil cooler and aftercooler mix (comes together) in the block and goes through the cylinder heads to the left and right water manifolds in the “vee” of the engine.



The bypass line goes from the temperature regulator housing to the inlet of the water pump. The regulators in the housing control coolant flow to the radiator or heat exchanger to regulate the temperature in the cooling system. When the coolant temperature is not high enough to open the regulators, the coolant will flow through the bypass line (bypassing the radiator) to circulate through the engine for quick warm-ups.

Four temperature regulators are in the thermostat housing.The housing has an upper and lower section. The sensing bulbs of the four temperature regulators are in the coolant in the lower section of the housing. Before the regulators open (upper inset), cold coolant is sent through the bypass line to the inlet of the water pump. As the temperature of the coolant increases to 88°C (180°F) and the regulators start to open (lower inset), coolant flow in the bypass line is stopped and coolant is sent through the outlets to the radiator or heatexchanger.
Coolant capacity is given in the Operation Guide for the engine only. Total system capacity will depend on the size of the radiator or heat exchanger. To prevent the coolant from freezing, it should have a mixture of 50 percent pure water, 50 percent
permanent antifreeze and a 3 to 6 percent concentration of corrosion inhibitor.



Here we see the housing for the temperature regulators (thermostats) and the four sleeve-type temperature regulators. The housing of the temperature regulator is above the front gear cover and supported by a compartment connected to the right and left water manifolds that are located above the cylinder heads.
Each of the regulators is positioned in a counterbore and has a lip-type seal.



Here the temperature regulator and seal have been removed from the housing. The smaller barrel portion of the regulator is the part that comes in contact with the seal.

When the regulator is closed (engine cold) coolant goes through the regulators. The coolant returns to the inlet of the water pump by way of the bypass
pipe (which is fastened to the opening in the front of the housing)

and does not get to the radiator.
When the regulator is open (engine hot) coolant goes through the

regulator out the side of the housingand then to the radiator for

cooling. On marine applications, the position of the regulator housing

will be upside down from the position in the photo.



The seals can be removed and replaced. To replace the seals, a seal driver must be used. To replace a seal, remove the old seal and clean the counterbore. Now install the seal in the housing with the lip of the seal away from the regulator.

Use a 1P529 Handle and a 1P489 Drive Plate to drive the seal into position in the housing.
When regulators and seals are replaced, the machinedsurfaces of the housing and cover must becleaned and a new gasket installed.

COOLING SYSTEM GENERATOR SET
On the right, we can see the coolant outlet line and the coolant inlet line at the bottom. The outlet line and inlet line are connected to a radiator outside the building.

The bypass line goes from the top of the thermostat housing to the inlet side of the water pump. We can also see the fuel filter housing and oil filter
housing on this generator set arrangement.