Signature Tests for Certain 797B Off-Highway Trucks{7601} Caterpillar

Signature Tests for Certain 797B Off-Highway Trucks{7601}

Usage:

797B JSM

Off-Highway Truck/Tractor:: 797B (S/N: JSM1-UP)

Introduction

This Special Instruction enables dealers and customers to benefit from use of the Cat VIMS by using VIMS to measure and record machine data while the truck is operated under specific sets of conditions. Every effort has been made to provide the most current and relevant information known to Caterpillar Inc.. Since Caterpillar makes ongoing changes and improvements to the products, this Special Instruction must be used with the latest technical information available from Caterpillar to ensure that such changes and improvements are incorporated where applicable.

For VIMS / DSN Support contact the local technical communicator.

Summary

This Special Instruction describes signature tests that can be run on an operational 797 Off-Highway Truck equipped with VIMS to record and analyze vital machine information data. Then the data can be compared to earlier data from the same machine, or to other similar machines in the fleet, to assist in identifying major component degradation or problems that have gone undetected by more conventional inspections.

Signature stationary tests include:

Brake System Testing & Operating Temperatures.

Starting Test.

Unloaded Engine Test.

Converter Stall Test for Front Engine.

Converter Stall Test for Rear Engine.

After the tests have been run and data downloaded from the VIMS, the truck can be put back on the ready line. Data is analyzed using VIMSpc and in some cases a spreadsheet program.

Data from signature tests is primarily used as a trending indicator. If tests are run when the truck is new, and then repeated at 2,000 service hours or 4,000 service hours, the rate of degradation for various machine systems can be monitored and repair scheduled in a cost effective manner.

Data from the signature tests can also be used for evaluation of truck performance. Some system-specific data analysis techniques are described that can be used to identify potential problems with the truck. These problems are such that it is unlikely that they are severe enough to cause a fault to be displayed on the monitor, logged on the event recorder, or be noticed by the operator. However, early identification of these problems will allow timely trouble shooting and repair scheduling, if needed. As a result, unscheduled repairs can be reduced.

If the truck meets the requirements for these tests, it can be expected to give normal performance on the haul road.

Recording Test Conditions

Many of the tests described in this Special Instruction will require keeping a record of the conditions (grade of road and surface condition) under which the tests were run. A paper or electronic file that describes SELD7026 the test conditions should be maintained.

A recommended method for creating an electronic reference file is to use the text editor in Windows Program Manager. To create the text file, access Programs / Accessories and open the Notepad program double clicking the Notepad icon. Type in the desired text that describes the particular conditions related to the test. Name and save the file to the desired sub directory that contains the datalogger file for the current machine. Double clicking the file name in File Manager with the mouse will enable the selection and reading of the text file at a later date.

Important Safety Information

Do not perform any procedure in this Special Instruction until you have read this Special Instruction and you understand this information. Use only proper tools and observe all precautions that pertain to the use of those tools. Failure to follow these procedures can result in personal injury. The following procedures should also be observed.

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs.

A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools in order to perform these functions properly.

Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard.

Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. Ensure that any tool, procedure, work method, or operating technique you use that is not recommended by Caterpillar is safe.

Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or repair procedures used.

Note: Caterpillar recommends that each customer conducts a risk assessment for remote control operation and establish layers of protection in and around the area of the remote controlled machine and establish safe job site procedures. Examples may include personnel training, warning signs, and barricades.

Note: Prior to operation of the machine read the Operation and Maintenance Manual.

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Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings could result in injury or death. Contact any Caterpillar dealer for replacement manuals. Proper care is your responsibility.

Stationary Tests

Purpose

The purpose of the stationary tests is to record key information on the engine, power train system, and electrical system that is monitored by the VIMS sensors. Stationary tests can be run on the vehicle near the truck shop, access to a haul road is not required. Information from the stationary tests can be compared to:

Expected normal values,

Earlier tests ran on the same machine, or

Tests that have been run on similar machines.

When the information is compared, the overall condition of the machine systems can be determined without the need for more time consuming installation of service tools.

The data logger and event recorder should be downloaded and cleared before beginning these tests. All five tests can be completed sequentially with the data logger turned on at the beginning of Test 2 and left on for the remaining tests. Estimated time to run all five tests is 0.5 hours if the machine is at operating temperature. If systems are not warmed, additional time will be required.

Test 1: Brake System Testing and Operating Temperatures

The purpose of this test is to warm the machine to normal operating temperatures and to verify that the brake system is functional. The test is not intended to measure maximum brake holding effort. Brake holding effort required to hold a machine at a specific engine rpm will vary from machine to machine due to differences in engine power setting, power train efficiency, and so on, and in brake holding capability.

Engine rpm at beginning of machine movement, with secondary brake applied, should be compared with the engine rpm the specific machine was able to hold on a prior test.

Start the engine and allow air system pressure to build up to maximum operating pressure.

Warm the engine and power train such that:
1. Coolant outlet temperature (ENG COOL TEMP) is between 79° C (175° F) to 90° C (195° F).
1. Converter outlet oil temperature (TC OUT TEMP) is between 82° C (180° F) to 90° C (195° F).
1. Transmission lube temperature (TRN LUBE TEMP) is between 79° C (175° F) to 90° C (195° F).

Apply secondary brake.

Move the transmission shift lever to first gear range forward.

Release the parking brake.

Gradually accelerate the engine to 1200 rpm.

The machine should not move forward.

If the secondary brake does not function properly, have necessary repairs made. Repeat this test with the service brakes. If truck creeps forward at full engine speed, have necessary repairs made before continuing the stationary tests.
Note: New trucks or trucks with newly rebuilt brakes may not hold completely until the brakes have been somewhat worn in.

Set the parking brake and shut down the engine.

Test 2: Starting Test

The purpose of this test is to record engine cranking speed. If the truck has a prelube system installed, prelube oil pressure and system voltage drop during prelube will also be recorded.

Note: This test will deplete the air system, run only if an alternate air source is available for recharging the air system.

Set the ground level shut off in the "FUEL OFF" position.

Turn key switch to the on position, allow VIMS to go through self-test.

Verify that air pressure is 827 kPa (120 psi). If not, recharge the air system.

Turn ON the data logger.

Crank the engine until cranking stops because of low air pressure.

Turn the data logger OFF.

Recharge the air system.

Set the ground level shut off in the "RUN" position.

Important channels to monitor during this test are:

Engine Speed
System air pressure
Engine oil pressure front
Engine oil pressure rear
System voltage

Test 3: Unloaded Engine Test

The purpose of this test is to record electrical system charging voltage and engine lubrication pressure as engine speed is increased. The time required to recharge the air system pressure is also recorded.

Turn key switch to the ON position, allow VIMS to go through self diagnostic test.

Turn the data logger ON.

Wait about 5 seconds.

Start the engine.

Run engine at low idle for 20 seconds.

Leave transmission in Neutral and gradually increase engine speed from low idle to high idle in 15 seconds. Hold at high idle for 10 seconds.

Reduce engine speed to low idle.

With transmission still in Neutral, snap accelerate engine speed from low idle to high idle two times with 15 seconds between accelerations.

Reduce engine speed to low idle.

Important channels to monitor during this test are:

Engine speed
System air pressure
Engine oil pressure front
Engine oil pressure rear
System voltage

Test 4: Converter Stall Test for Front Engine

The purpose of this test is to record the front engine response time and maximum engine speed developed against converter stall.

Note: Do not apply the parking brake during the converter stall test. On VIMS equipped machines, applying the parking brake with the transmission in gear will cause a category 3 parking brake warning message to lock on the message center. This condition will prevent the serviceman from observing when the category 2 warning occurs from hot converter oil temperature during the stall test.

Position the machine on ground level at least 50 m (164 ft) from other machines, structures, or people.

Chock the wheels to prevent movement of the machine.

Connect CAT ET Service Tool and disable injection for the rear engine.

Apply the service brake and retarder, shift the transmission to first gear forward.

Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce the engine speed to a low idle and shift the transmission to Neutral.

Turn ON the datalogger.

Apply the service brake and retarder, shift the transmission to first gear forward.

Quickly accelerate the engine from low idle to maximum speed. Hold at maximum engine speed for 5 to 10 seconds or until the high torque converter oil temperature warning comes on (Category 2).

Reduce the engine speed to a low idle and shift the transmission to Neutral. Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Repeat step 8, 9, and 10.

Reduce the engine speed to low idle. Turn data logger OFF.

Allow system to cool to normal ranges.

Important channels to monitor during this test are:

Engine speed
Torque converter temperature
Exhaust temperature left front
Exhaust temperature right front
Boost pressure front

Test 5: Double Stall Test for Front Engine

The purpose of this test is to record the front engine response time and maximum engine speed developed against converter stall and the hoist hydraulic system pump.

Position the machine on ground level at least 50 m (164 ft) from other machines, structures, or people.

Chock the wheels to prevent movement of the machine.

Connect CAT ET Service Tool and disable injection for the rear engine.

Apply the service brake and retarder, shift the transmission to first gear forward.

Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce the engine speed to a low idle and shift the transmission to Neutral.

Turn ON the datalogger.

With the service brakes and retarder applied, move body raise lever to BED DOWN position, move the transmission shift lever to first gear forward range.

Quickly accelerate the engine from low idle to maximum speed. Hold at maximum engine speed for 5 to 10 seconds or until the high torque converter oil temperature warning comes on (Category 2).

Lower the engine speed to a low idle and shift the transmission to Neutral, and move body raise lever to "FLOAT" position. Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce engine speed to low idle.

Repeat step 8, 9, 10, and 11.

Turn data logger OFF.

Allow system to cool to normal ranges.

Important channels to monitor during this test are:

Engine speed
Torque converter temperature
Exhaust temperature left front
Exhaust temperature right front
Boost pressure front

Test 6: Converter Stall Test for Rear Engine

The purpose of this test is to record the front engine response time and maximum engine speed developed against converter stall.

Position the machine on ground level at least 50 m (164 ft) from other machines, structures, or people.

Chock the wheels to prevent movement of the machine.

Connect Cat ET and disable injection for the rear engine.

Apply the service brake and retarder, shift the transmission to first gear forward.

Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce the engine speed to a low idle and shift the transmission to Neutral.

Turn ON the datalogger.

Apply the service brakes and retarder, shift the transmission to first gear forward.

Quickly accelerate the engine from low idle to maximum speed. Hold at maximum engine speed for 5 to 10 seconds or until the high torque converter oil temperature warning comes on (Category 2).

Reduce the engine speed to low idle. Shift the transmission to Neutral. Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Repeat step 8, 9, and 10.

Reduce engine speed to low idle. Turn data logger OFF.

Allow system to cool to normal ranges.

Important channels to monitor during this test are:

Engine speed
Torque converter temperature
Exhaust temperature left rear
Exhaust temperature right rear
Boost pressure rear

Test 7: Double Stall Test for Rear Engine

The purpose of this test is to record the front engine response time and maximum engine speed developed against converter stall and the hoist hydraulic system pump.

Position the machine on ground level at least 50 m (164 ft) from other machines, structures, or people.

Chock the wheels to prevent movement of the machine.

Connect Cat ET and disable injection for the rear engine.

Apply the service brake and retarder, shift the transmission to first gear forward.

Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce the engine speed to a low idle and shift the transmission to Neutral.

Turn ON the datalogger.

With the service brakes and retarder applied, move body raise lever to BED DOWN position, move the transmission shift lever to first gear forward range.

Quickly accelerate the engine from low idle to maximum speed. Hold at maximum engine speed for 5 to 10 seconds or until the high torque converter oil temperature warning comes on (Category 2).

Lower the engine speed to a low idle and shift the transmission to Neutral, and move body raise lever to "FLOAT" position. Raise the engine speed to about 1600 rpm and hold until torque converter oil temperature warms to 98.9° C (210° F).

Reduce engine speed to low idle.

Repeat step 8, 9, 10, and 11.

Turn data logger OFF.

Allow system to cool to normal ranges.

Important channels to monitor during this test are:

Engine speed
Torque converter temperature
Exhaust temperature left rear
Exhaust temperature right rear
Boost pressure rear

Download Data and Clear VIMS

At the completion of the Truck Signature Tests, the data logger and event recorder should be downloaded and cleared.

None of the tests described in this Special Instruction should cause VIMS to display a level 3 warning to the operator or log a level 3 event. If any level 3 events are present, they should be investigated and appropriate repair made. Use the methods described in the Service Manual for troubleshooting.

Analysis of Signature Test Data

Engine

Problem 1: Exhaust Temperature Split Too High

Exhaust temperature split is the difference between the right exhaust temperature and the left exhaust temperature taken at the same time. Left and right exhaust temperatures are measured at full load conditions during the following tests.

Stationary Test 4 - Converter Stall

Stationary Test 5 - Double Stall

The exhaust temperature split will likely be highest for the Double Stall test.

A normally performing engine has some variation in the bank-to-bank exhaust temperature difference, typically less than 20° C (36° F). An exhaust temperature split greater than 50° C (90° F) or a step change in the exhaust temperature split occurs, this may indicate a serious problem.

Probable Cause:

Faulty exhaust temperature sensor

Defect in fuel injector

Leak or break in fuel line between fuel manifold and cylinder head

Wrong valve lash

Air inlet system has a leak

Exhaust system has a leak

Air inlet or exhaust system has a restriction

Wrong fuel Injector lash

Incorrect fuel injection timing calibration

Bent or broken push rod

Problem with electronic control system

Note: Refer to Testing & Adjusting, SENR5596, "3512 and 3516 EUI Engines for Caterpillar Built Machines ", for troubleshooting the engine.

Problem 2: Engine Has Low Oil Pressure

A decrease in engine oil pressure, although the pressure is still within the acceptable range since the last test, is an indication that parts (engine bearings, engine oil pump, engine oil pump relief valve, and so on) are beginning to fail.

Engine oil pressure versus engine speed data can be derived from several of the stationary tests. Stationary Test 3 - Unloaded Engine Test is the best source since the engine speed is raised slowly. The Data Logger plot shown on the next page is a typical run.

This data can be reduced to produce a plot of engine oil pressure versus engine speed. Since VIMS does not have capability to plot one sensor output versus another sensor one of several alternate approaches can be used. Two approaches are:

Using VIMS Analysis read the actual values of oil pressure and engine speed and plot the values in another program such as a spreadsheet.

Using VIMS Analysis, export the data to a separate file and then import this file into a spreadsheet or other data analysis or plotting program.

The graph shown in Illustration 2 is generated using the data from the Data Logger run as plotted in the Illustration 1.

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Illustration 1	g02931879

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Illustration 2	g02940275

The straight-line curve in Illustration 2 represents the oil pressure versus engine speed warning level that is used by the Engine Control Module (ECM) and VIMS to provide low oil pressure warning. Oil pressure is checked against these curves according to engine speed. Refer to Testing & Adjusting, SENR5596, "3512 and 3516 EUI Engines for Caterpillar Built Machines ", for further definition of this oil pressure map.

The measured oil pressure for this engine is well above the warning level curves. The change in slope of the measured oil pressure occurs at the engine speed where the relief valve is beginning to open. As an engine and lubrication system wears, the speed at which the relief valve begins to open will increase. When a 20 percent increase in engine rpm is necessary to generate maximum (oil-over-relief) oil pressure, this may be an indicator that repair or rebuild is needed.

If the same viscosity oil is used and the oil temperature is the same and there are significant changes in oil pressure, determine the reason and make repairs as needed.