Product Support Program For Increasing Performance On Certain 140H And 143H Motor Graders Equipped With VHP Caterpillar

Product Support Program For Increasing Performance On Certain 140H And 143H Motor Graders Equipped With VHP

Usage:

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Caterpillar: Confidential Yellow

NOTE: This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS4593" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.

NOTE: This Revised Service Letter replaces the October 14, 1998 (Revised March 2000) Service Letter. Changes have been made to the Affected Product.

Termination Date

October 31, 2002

Problem

There have been complaints relating to performance (ability to go up grades or plow snow) on certain 140H and 143H Motor Graders equipped with VHP.

Affected Product
Model & Identification Number

140H (2ZK1-4817, 9TN1-1024, 9ZN1-357)

143H (1AL1-769)

Parts Needed

1 - 1287794 BOLT

1 - 1287796 BOLT

1 - 1592434 PLATE

Action Required

NOTE: For fuel setting instructions reference 3306B Engine Systems Operation Testing & Adjusting Service Manual SENR5594. Also, see the attached procedure for the correct interpretation of variable HP torque curves for motor graders.

Adjust engine fuel setting to obtain net engine power increase of (+10). The rework requires that both the low end and high fuel settings be changed. Use the high and low test specs in the chart below correspinding with the correct engine arrangement in the motor grader.

These new test specs are available on aims:

TMI-General Engine Data, use option (ESRS OT'S) spec list. After adjustment the net horse power @ 1900 RPM IS 195/165.

NOTE: Power increase results in a lower altitiude capability before de-rate:

140H DROPS FROM 8789 TO 7215 FT

143H DROPS FROM 7690 TO 6158 FT

(REF. 140G-7382).

Service Claim Allowances

NOTE: This is a 1.5-hour job.

Parts Disposition

Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Attach.

(1-Rework Procedure)

Rework Procedure

Problem:

There has been much misinterpretation of the REFERENCE Service Magazine article as relates to the Variable Horsepower (VHP) engines for these motor graders. In addition, there have been errors in the publishing of engine test history for the two VHP power settings in the Technical Marketing Information (TMI). Also, there is no Special Instructions procedure available for setting the VHP solenoid for the low horsepower setting on these motor graders. These factors have combined to allow significant confusion in regards to resetting the fuel settings for these machines with the VHP (variable horsepower) engine feature.

CORRECT INTERPRETATION OF THE REFERENCE SERVICE MAGAZINE ARTICLE

The REFERENCE Service Magazine article is still valid as a description of the "dog leg" dual horsepower torque curves for the above motor graders. However, in order to fully understand and interpret its contents clearly, the following additional background information is needed:

1. Both Illustrations 1 and 2 in the article are LUG curves, not POWER curves. Although TORQUE rises along a lug curve, POWER usually drops unless the torque rise is sufficient to overcome the loss in engine speed (Power is equal to torque times rpm, divided by a constant).

Illustration 1. Typical single power "dog leg" torque curve. Engine speed in rpm is on the horizontal axis. Torque is on the vertical axis.

Illustration 2. Typical dual power "dog leg" torque curve. Engine speed in rpm is on the horizontal axis. Torque is on the vertical axis.

2. The purpose of the "DOG LEG" portion of the HIGH POWER lug curve (between POINTS 1 and 3 in Illustration 1) is to improve the ease of shifting of the transmission during high gear operation when high torque rise is a plus. The result is smoother machine operation.

3. The "dog leg" shape in the High Power lug curve is the result of the Full Load (FL) power screw compressing a very soft torque spring (actually two torque springs sandwiched together) from between Points 1 and 3 in Illustration 1. At Point 3 the torque spring is completely collapsed, and further torque rise below 1900 rpm is called NATURAL TORQUE RISE.

4. The purpose of the LOW POWER lug curve, which has NATURAL TORQUE RISE only, is to provide protection of the drive train components from excessive torque during low gear operation of the machine.

5. The purpose of the LOW POWER lug curve, which has NATURAL TORQUE RISE only, is to provide protection of the drive train components from excessive torque during low gear operation of the machine.

Segment 1: The OVERRUN CURVE from the no-load high idle speed to POINT 1, when the FL power screw begins to compress the torque spring.POINT 1 also corresponds to the CORRECTED FULL LOAD (FL) POWER AND SPEED shown on the HIGH POWER TEST SPECIFICATION. A continuity light is used to check this point (actually the SET POINT speed is about 50 rpm higher for repeatability) and calibrate the Full Load Static Fuel Setting (FL ST F SET) in the high power test specification.

Segment 2: The "DOG LEG" CURVE for the motor graders has a HIGH TORQUE RISE that begins at POINT 1 (Illustration 1) of the high power lug curve at 2100 rpm. As the engine lugs down from 2100 rpm, the FL power screw compresses the torque spring. This spring has a very soft spring rate for more fuel rack per drop in engine speed rpm, resulting in a large torque rise. At the 1900 rpm RATED SPEED, the torque spring is completely compressed. The high torque rise along Segment 2 also results in an increase in engine power from 2100 rpm to 1900 rpm. The GROSS ENGINE POWER of POINT 3 (Illustration 1) is greater than the gross engine power for POINT 1, and does in fact correspond to the MAXIMUM POWER point of the engine. Note the difference between GROSS POWER and NET or ADVERTISED POWER is the parasitic loads from the fan, alternator, muffler, air cleaner, and air conditioner compressor. The advertised power rating of any Caterpillar machine usually corresponds to the point of maximum power, and thus the 1900 rpm speed is used for the advertised rating instead of the test power 2100 rpm.

Segment 3: Engine operation between POINT 3, the rated point, and POINT 2, which corresponds to the PEAK TORQUE TEST POINT, is the third segment of the high power "dog leg" curve. Along this curve segment, there is only NATURAL TORQUE RISE. Natural torque rise is due to the increase in fuel efficiency of the engine that results as the speed drops. This segment has a relatively low torque rise compared to that in Segment 2, resulting in engine power dropping from the maximum power at 1900 rpm rated speed.

Segment 4: Below the peak torque test point, POINT 2 in Illustration 1, further torque rise is natural as the FT ST F SET screw setting limits further fuel rack travel. Note POINT 2 is a test point used to evaluate the engine performance during factory test, and rarely corresponds exactly to the actual peak torque speed of the engine which often occurs at a lower speed.

6. The DOTTED CURVE shown in Illustration 2 is the LOW POWER LUG CURVE. The main characteristic of this curve is the torque rise is strictly natural. Further fuel rack travel beyond the identical FL ST F SET and FT ST F SET settings on the low power test specification is limited by the solenoid plunger.

7. The LOW POWER curve has two important points. POINT 3 (Illustration 2) corresponds to the RATED TEST POWER point at the same rated engine speed as the high power curve. POINT 4 is the LOW POWER PEAK TORQUE TEST point. These points are important for test reasons only, and are necessary to ensure the solenoid setting and engine performance meet the design specifications for proper operation of the motor grader machine and drive train during low gear operation.

8. POINT 1 in Illustration 2 DOES NOT APPLY OR HAVE ANY SIGNIFICANCE TO THE LOW POWER LUG CURVE. The low power lug curve actually begins below the 2100 rpm speed that corresponds to POINT 1 on the high power lug curve. The FL ST F SET for the low power curve is between the FL ST F SET and the FT ST F SET for the high power lug curve. The correct intersection of the dotted low power curve and the solid high power curve in Illustration 2 would be somewhere in Segment 2 of the "dog leg" high power lug curve.

TEST HISTORY INTERPRETATION IN THE TMI

Prior to August 1997 there were two problems with the VHP engine test history in the TMI. First, only the low power test history was displayed in an inquiry in GKN401-05. Secondly, if the low power test specification called for a setting of "0.00mm", the TMI displayed this as an open field. This was often misinterpreted as "no setting". Now, both these problems have been corrected. The results should clear up any difficulty getting the correct factory specifications for resetting any VHP motor grader engine.

TEST SPECIFICATION INTERPRETATION IN THE TMI

In GKN401-06 the details of any test specification can be viewed. It is important to remember to enter the engine serial number along with the specification number to ensure the specification data is applicable to the engine vintage. Test specifications are modified as more engines are built to ensure the settings correspond to the tolerance stack ups of the parts used in the engines at that time. Normally, these drifts are small, but the correct serial number range for your engine should be used to get a matching test specifications with what is shown on the engine information plate on the valve cover. Note that sometimes serial number ranges for test specifications do not show the correct settings stamped on the engine information decal. This is a problem that will be investigated. ALWAYS REFER TO THE SPECIFICATION SETTINGS SHOWN IN THE ENGINE TEST HISTORY OR THE INFORMATION DECAL LOCATED ON THE VALVE COVER FOR USE IN FUEL SYSTEM ADJUSTMENTS AND RESETTING.

ENGINE INFORMATION DECAL INTERPRETATION

The information decal on the valve cover of your engine shows the correct fuel settings for your engine, and corresponds with those shown in the engine test history. THE RATED POWER AND SPEED SHOWN IS THE ADVERTISED HIGH POWER RATING AND HAS NO RELATIONSHIP TO THE TEST POWER AND SPEED SHOWN ON THE HIGH POWER TEST SPECIFICATION. Remember the FL ST F SET in the high power test specification is for 2100 rpm in the motor graders, and not the 1900 rpm rated speed.

VHP SOLENOID ENGINE FUEL PUMP SETTINGS PROCEDURE

Check and adjust the HIGH POWER specification settings with the Fuel - Air Ratio Control (FARC) or smoke limiter and the VHP solenoid removed from the back end of the governor housing. Use the 6V-7941 Compressor Assembly only with the VHP solenoid removed to check or adjust the high power Full Load and Full Torque static fuel specification settings per the Systems Operation Testing & Adjusting manual for the engine. Use the following procedure to check and adjust the LOW POWER Full Load static fuel specification setting:

1. Remove the fuel pump cover and place the zero pin in the rack slot.

2. Clear all readings on the electronic rack position indicator, move the pointer to actual field, zero the indicator. The throttle should be held fully open.

3. Install the VHP solenoid on the rear of the governor housing.

4. Remove the zero pin.

5. Apply pressure to the governor control shaft in the opening direction to fully#20open the throttle.

6. Back out (unscrew) the VHP solenoid. The reading on the indicator should be within ± 0.13 mm of the Full Torque fuel setting on the high power setting specification.

7. Rotate (screw in) the VHP solenoid to the specified low power Full Load fuel setting.

NOTE: Do not exceed FL setting, as Steps 5 through 7 must be repeated in order to achieve the correct setting.

8. Lock the VHP solenoid.

9. Recheck the setting by moving the throttle to shut off and then back to full open.

10. Remove the indicator and install the cover on the pump.

11. Install the FARC or smoke limiter on the rear of the governor housing.

NOTE: If the low power FL fuel solenoid setting is positive, the electronic indicator should be reading positive numbers and the numbers will decrease until the desired setting.

NOTE: If the low power FL fuel solenoid setting is negative, the numbers on the indicator will start out as positive if the FT fuel setting of the high power test specification is positive. As the solenoid is rotated (screwed in) the numbers will decrease to zero, and then increase in the negative direction.

NOTE: Remove original engine information plate. Stamp the new blank plate with the necessary engine information, including the new fuel settings. Reflatten plate after stamping and install on engine using 8T9021 adhesive.