3412 Generator Set Engines Caterpillar

Restriction of Air Inlet and Exhaust

There will be a reduction in the performance of the engine if there is a restriction in the air inlet system or the exhaust system.

The air flow through a used air cleaner may have a restriction. The air flow through a plugged air cleaner will be restricted to some degree. In either case, the restriction must not be more than the following amount:

• 7.5 kPa (30 in H₂O)

Back pressure is the difference in the pressure between the exhaust at the outlet elbow and the atmospheric air. Back pressure from the exhaust must not be more than the following amount:

• 6.7 kPa (27 in H₂O)

Measurement of Pressure in Inlet Manifold

The efficiency of an engine can be checked by making a comparison of the pressure in the inlet manifold with the information in the Technical Marketing Information (TMI).

This test is used when there is a decrease of horsepower from the engine, yet there is no actual sign of a problem with the engine.

The correct pressure for the inlet manifold is also given in the Technical Marketing Information (TMI), "Fuel Setting and Related Information". These standards are established under the following conditions:

• 96 kPa (29 Inches Hg) dry barometric pressure.

• 29°C (85°F) outside air temperature

• 35 API rated fuel

Any change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower inlet manifold pressure measurement than the pressure in the TMI. Outside air that has both a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.

A difference in fuel density will change horsepower (stall speed) and boost. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that appears in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that appears in the TMI. BE SURE THAT THE AIR INLET OR THE EXHAUST DOES NOT HAVE A RESTRICTION WHEN YOU ARE MAKING A CHECK OF THE PRESSURE.

Use 1U-5470 Engine Pressure Group to check the pressure in the inlet manifold.

Remove the plug on the aftercooler housing in order to measure inlet manifold pressure.

Illustration 1	g00293196
1U-5470 Engine Pressure Group

This tool group has a gauge to read pressure in the inlet manifold. Refer to Special Instruction, SEHS8524 for the operation of this tool group.

Turbocharger

Inspect the bearing of the turbocharger if any unusual sound or vibration is noticed.

A quick check of the bearing condition can be made without disassembling the turbocharger. This can be done by removing the piping from the turbocharger and inspecting the following items.

• The compressor impeller

• The turbine wheel

• The compressor cover

Rotate the compressor and the turbine wheel assembly by hand and observe by feeling excess end play. The rotating assembly should rotate freely. There should be no rubbing or binding of the rotating assembly. If there is any indication of the impeller rubbing the compressor cover or the turbine wheel rubbing the turbine housing, replace the turbocharger with a new or rebuilt turbocharger.

Illustration 2	g00320945
Checking turbocharger rotating assembly end play (typical example)

End play is checked with a dial indicator. Attach a dial indicator with the indicator point on the end of the shaft. Move the shaft from end to end. Make a note of the total indicator reading.

If the end play is more than the maximum end play, rebuild the turbocharger or replace the turbocharger. End play that is less than the minimum could indicate that there is carbon build up on the turbine wheel. The turbocharger should be disassembled for cleaning and inspection.

A more reliable check of the bearing conditions can be made only when the turbocharger is disassembled. The bearings, the shaft journal, and the housing bore diameters can actually be measured.

Note: Do not cock the shaft. This could result in a false reading.

Measurement of Exhaust Temperature

Use the 123-6700 Infrared Thermometer to check this exhaust temperature. You can find operating instructions and maintenance instructions inside the Operator's Manual, NEHS0630, "123-6700 Infrared Thermometer II with Laser Sighting".

Crankcase (Crankshaft Compartment) Pressure

Pistons or rings that have damage can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will be more than the normal amount of fumes rising from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. This crankcase pressure can also be the cause of any oil leakage at the gaskets and at the seals. These areas would not normally have leakage.

Note: The electronic service tool can be used to measure crankcase pressure.

Illustration 3	g00286269
8T-2700 Blowby/Air Flow Indicator

The 8T-2700 Blowby/Air Flow Indicator checks the amount of blowby. See Special Instructions, SEHS8712 for more information on using this tool.

Compression

An engine that runs roughly can have a leak at the valves. An engine that runs roughly can also have valves that need an adjustment. Remove the head and inspect the valves and valve seats. This is necessary to find those small defects that do not normally cause a problem. Repairs of these problems are normally done when you are reconditioning the engine.

Cylinder Head

The cylinder heads consist of three main components that can be removed:

• valve seat inserts

• valve guides

• bridge dowels

When any of these components are worn or when these components are damaged, these components can be removed. Refer to Disassembly and Assembly for the replacement of these components.

Bridge Adjustment

When the head is disassembled, keep the bridges with the respective cylinders. Adjustment of the bridge will be necessary for the following reasons.

• the valves are ground

• reconditioning of the cylinder head is completed

The bridge should be checked and/or adjusted each time the valves are adjusted. Use the procedure that follows to make an adjustment to the bridge.

Illustration 4	g00363479
Bridge adjustment

Note: Valves must be fully closed.

1. Apply engine oil on the bridge dowel in the cylinder head. Apply engine oil in the bore in the bridge.

2. Install the bridge with the adjustment screw toward the exhaust manifold.

3. Loosen the locknut for the adjustment screw. Loosen the adjustment screw for several turns.

4. Put a force on the bridge with a finger. This will keep the bridge in contact with the valve stem opposite the adjustment screw.

5. Turn the adjustment screw clockwise until the adjustment screw makes contact with the valve stem. Then, turn the adjustment screw 30 degrees more in a clockwise direction. This will make the bridge straight on the dowel. Also, this will make compensation for the clearance in the threads of the adjustment screw.

6. Hold the adjustment screw in this position. Tighten the locknut to 28 ± 4 N·m (21 ± 3 lb ft).

7. Apply engine oil at the point that the rocker arm makes contact with the bridge.

Valve Lash Setting

Valve lash is measured between the rocker arm and the bridge for the inlet valves. Valve lash is measured between the rocker arm and the valve stem for the exhaust valve. All of the clearance measurements and the adjustments must be made with the engine stopped. The valves must be FULLY CLOSED.

Valve Lash Check: Engine Stopped

An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. The range is given in Table 3.

Illustration 5	g00363480
Valve lash

Note: Inlet and exhaust valve lash adjustments should be made at the first recommended oil change. Refer to Operation And Maintenance Manual for subsequent intervals.

Valve Lash Setting: Engine Stopped

To make an adjustment to the valve lash, turn the adjustment screw in the rocker arm. Valve lash adjustments can be made by using the following procedure:

Illustration 6	g00363481
Valve adjustment (typical example)

Illustration 7	g01246025
Cylinder and valve location (A) Inlet. (B) Exhaust. (C) Fuel injection pumps.

1. Put No. 1 piston at the top center position.

   Note: See Testing and Adjusting, "Finding Top Center Position for No. 1 Piston" for further details.

2. Make an adjustment to the valve lash on the inlet valves for cylinders 1, 3, 4, 6, 7, and 12. Make an adjustment to the valve lash on the exhaust valves for cylinders 1, 4, 5, 8, 9, and 12.

3. After each adjustment, tighten the nut for the valve adjustment screw to a torque of 30 ± 4 N·m (22 ± 3 lb ft). Then, check the adjustment again.

4. Remove the timing bolt and turn the flywheel by 360 degrees in the direction of the engine's rotation. This will position the No. 1 piston at the top center on the exhaust stroke. Install the timing bolt in the flywheel.

5. Make an adjustment to the valve lash on the inlet valves for cylinders 2, 5, 8, 9, 10, and 11. Make an adjustment to the valve lash on the exhaust valves for cylinders 2, 3, 6, 7, 10, and 11.

6. After each adjustment, tighten the nut for the valve adjustment screw to a torque of 30 ± 4 N·m (22 ± 3 lb ft). Then, check the adjustment again.

7. Remove the timing bolt from the flywheel after all valve lash adjustments have been made.

8. Recheck the valve lash on all twelve cylinders after the initial setting.