Product Support Program To Adjust The Engine Governor "Torque Limiter" Setting On Certain Challenger 55 Tractors Caterpillar

Product Support Program To Adjust The Engine Governor "Torque Limiter" Setting On Certain Challenger 55 Tractors

Usage:

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Caterpillar: Confidential Yellow

NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.

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 "PS8965" 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.

Termination Date

August 31, 1997

Problem

Some CH55 engines may have the governor torque limiter adjustment set incorrectly from the factory. The incorrect adjustment can result in very little torque rise as the engine is lugged below rated speed of 2100 rpm, and cause customer complaints of "low power" or poor response in the field. The CH35 and CH45 governors have different specifications, and were not affected by the incorrect factory adjustment procedure.

Affected Product
Model & Identification Number

CH55 (7DM1-334, 7DM511-Up7DM560, 7DM563-569, 7DM571-577, 7DM579-581, 7DM589-593 , 7DM595-604, 7DM606-607)

Parts Needed

1 - Dealer Seal and Lockwire for Governor (after adjustment)

1 - 1192940 Gasket-Valve Cover (only if needed)

1 - Dealer Seal and Lockwire for Fuel Setting (only if Static Fuel Setting has been adjusted)

Action Required

READJUST THE GOVERNOR TORQUE LIMITER SETTING:

The governor Torque Limiter setting can be re-adjusted. For this Program, the preferred method of adjustment is done on-machine using a PTO dynamometer and the attached Procedure, " PTO Dynamometer Adjustment of Governor Torque Limiter". This method is the easiest. In this case, it is not necessary to remove the governor from the engine.

- The PTO dynamometer is used to lug the engine so that the Torque Limiter adjustment can be set properly under load. This Program and the Procedure does not include a complete dynamometer test of horsepower.

- If a PTO dynamometer is not available to perform the Torque Limiter adjustment, it will be necessary to remove the governor from the engine, and adjust the Torque Limiter setting on the Governor Calibration Bench. An abbreviated procedure, " Governor Calibration Bench Adjustment of Governor Torque Limiter" for the CH55 governor is attached for the purpose of checking & setting the Torque Limiter only.The Governor Calibration Bench adjustment procedure will take longer, due to time needed to removestall the governor from the engine, and to check the Static Fuel Setting of the engine after the governor has been re-installed on the engine.

- Some machines may have previously had a dealer adjustment of the engine Static Fuel Setting because of a low power complaint.When performing this Program, if machine has a "red" dealer seal on the Static Fuel Setting (under the valve cover), the Static Fuel Setting should be checked, and reset (if needed) to the Static Fuel Setting specification listed on the Engine Information Plate (Label), within ± 0.10mm.The original factory seals are "yellow".

DISCUSSION - The CH55 Engine Governor is equipped with an externally adjusted "Torque Limiter" to provide a limit on the amount of torque-rise that the governor can provide.The internal torque-cam of the CH55 governor provides extra torque rise (increases dynamic rack) as the engine lugs below the rated speed of 2100 rpm.At 1900 rpm lug (2000 rpm lug on earlier CH55s), theTorque Limiter acts directly on the servo to limit the maximum governor output and prevent any further increase in dynamic rack due to the torque cam.When the governor servo contacts the Torque Limiter screw during lug, no further dynamic rack increase can occur as the engine lugs down, and engine is then limited to its "natural" torque rise.The torque limiter adjustment is originally set during governor calibration at the factory.

The governor Torque Limiter feature is used to assure the engine cannot exceed its operating limits (cylinder pressures & temperatures, exhaust temps, etc) if engine is lugged below 1900 rpm. Excessive torque rise below 1900 rpm could result in overheating and/or engine damage such as head gasket failures or burned valves.

Service Claim Allowances

If PTO dynamometer is not available, and governor is removed for bench test according to the alternate procedure provided, then the labor allowance is:

Parts Disposition

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

Attach.

(1-Rework Procedure)

Rework Procedure

PTO Dynamometer Adjustment of Governor Torque Limiter

(Preferred Method for This Program)

CH-55 Tractors Only

NOTE 1: If dealer has previously re-adjusted the Static Fuel Setting of the machine due to a "low-power" complaint, the Static Fuel Setting should be checked again, and reset to the Static Fuel Setting specification shown on the Engine Information label within ± 0.10mm. This should be done before making the Torque Limiter adjustment using the PTO dynamometer procedure shown below.If the original "yellow" factory seal is still in place on the Fuel Setting adjustment under the valve cover, then it is not necessary to check/adjust the Fuel Setting.Do not remove the seal from the Static Fuel Setting unless the setting is incorrect. The Static Fuel Setting can be checked without removing the seal. The seal and lockwire must be removed in order to make an adjustment of the static Fuel Setting.Dealer seals are "red" in color.

NOTE 2: Before beginning this test, dealer must examine the Governor Information Plate, and determine the Governor Group Number (GOV GRP).Adjustment depends upon which part number of governor the engine is equipped with.

1. Set up CH55 Tractor on PTO dynamometer. It will NOT be necessary to measure fuel flow, temperatures, etc for this abbreviated procedure to adjust the Torque Limiter. It is necessary to be able to monitor engine rpm, and to be able to stabilize and hold a full load (lug) condition for several minutes. Use of the 9U7400 Multitach Group (phototach), or equivalent, is recommended to monitor engine rpm while making the adjustment.

- Remove governor seal and lockwire

- Remove the small hexagonal-shaped cover-plug on the side of the governor so that the Torque Limiter adjustment screw is exposed.Refer to Illustration 1.

2. Warm up engine/machine briefly on PTO dyno, and run at full load for at least 5 minutes. It is not necessary to conduct an extensive warm up of the machine, and not necessary to stabilize oil and coolant temperatures.

3. Make sure engine is at "full throttle", so that governor control lever is in full contact with the High Idle adjustment screw.

4. Earlier Engines with 1135914 Governor - Use PTO dyno to lug engine to 1980 - 2000 rpm.

Later Engines with 1349898 Governor - Use PTO dyno to lug engine to 1880 - 1900 rpm.

Allow rpm to stabilize within this rpm range for at least 30-60 seconds.

5. Loosen locknut on Torque Limiter adjustment screw on side of governor. See Illustration 1.

6. With rpm stabilized within rpm range shown in Step 4, slowly back out the Torque Limiter adjustment screw (CCW) approximately turn while monitoring rpm.Engine rpm will remain constant, or may increase.

- If engine rpm increases when backing out the Torque Limiter adjustment screw, continue to back out screw slowly until rpm stops increasing, then back out screw an additional 1/4 turn to assure it no longer is affecting engine rpm.Go to Step 7.

- If engine rpm remains constant while backing out the adjustment screw, then stop after 1/4 turn, and proceed to Step 8.

7. If engine rpm increased when the adjustment screw was backed out during Step 6, then it may be necessary to increase the PTO dyno load slightly to stabilize the engine again within the correct rpm range listed below and in Step 4, before making the final adjustment in Step 8.

- 1135914 Governor - Stabilize at 1980-2000 rpm (Earlier Engines)

- 1349898 Governor - Stabilize at 1880-1900 rpm (Later Engines)

8. With engine rpm stabilized in lug condition listed above in Step 7 (also shown in Step 4), slowly turn the Torque Limiter adjustment screw "in" (CW) until engine speed drops 20-30 rpm. If necessary, repeat steps 6-8. Lock the adjustment screw in this position.

9. Remove the load and gradually reduce engine rpm. Allow engine to idle for about 5 minutes and then shut off engine. Install hexagonal cover-plug over the Torque Limit adjustment screw.

10. Install lockwire and dealer seal on governor housing; sealing the High Idle screw, the Torque Limiter cover-plug, and Fuel Ratio Control (FRC) cover plug. One lockwire and seal is used to "seal" all these items on the governor. Be sure plastic "seal" does not interfere with governor lever or linkage operation.

11. Stamp a "T" on the Governor Information Plate in the lower left-hand corner of the plate, just below the words "Lot No.", as shown in Illustration 2.

12. Make a Service Report (SIMS) entry, as follows:

Governor Calibration Bench Adjustment Of Torque Limiter

CH55 Tractor Only

This abbreviated procedure is intended only as an alternate means to check and adjust the CH55 Torque Limiter adjustment of the Governor "off-engine" on a Governor Calibration Bench, when a PTO Dynamometer is not available. This procedure and the Specifications listed apply only to the CH55 governor (113-5914 or 134-9898 Governors) and should not be used when complete governor bench calibration is needed, such as after a major governor repair or overhaul.Use TMI for complete Governor Specifications.

1. Remove the CH55 engine governor from the engine. Use Service Manual procedures for governor removal and installation. Be sure to keep the governor clevis pin (linkage pin) with the governor, as the pin is needed during bench testing.

NOTE: The RPM's referred to in this procedure are governor test bench rpms, and NOT engine rpm.

2. Install governor on Governor Calibration bench, and prepare it for bench test. Refer to the Governor Service Manual, Form SENR6454 (October 1994). This manual includes instructions for obtaining Governor Specifications from TMI. Always use the TMI to determine the complete governor test specifications for the particular GOVGRP part number and change level of the governor.

The "change level" is shown on the governor information plate just after the governor part number. For example,GOV GRP113 591403.In this example it is a 1135914 Governor, with change level 03. TMI provides governor specifications for each change level of a governor, if the change level is specified.

3. Pressurize and hold the Fuel Ratio Control to 20-30 PSI so that FRC cannot restrict governor output during this test. Use a pressure-regulated air supply.

4. Remove Governor Seal and Lockwire.

5. Remove small Hexagonal Cover over the Torque Limiter adjustment screw (Illustration 1).

6. Loosen Torque Limiter locknut, and back out (turn CCW) the adjustment screw at least two (2) full turns, before testing the governor.

- Be sure to follow Governor Service Manual procedures when testing, such as lowering governor rpm slowly to the desired test rpm from at least 100 rpm above thetest rpm. The Torque Limiter Adj. is a new feature used only on certain applications, and is not yet described in the Governor Service Manual. However, the procedures for adjusting bench rpm, making the adjustment, and rechecking it are similar to those forthe Load Stop adjustment. The Torque Limiter must be checked with the Fuel Ratio Control (FRC) pressurized to 20-30 psi, so the FRC does not restrict governor output.

7. Run governor on bench. Increase test bench rpm to approximately 1500 rpm. Be sure FRC remains pressurized.

- Do not loosen or make changes to the High Idle (throttle stop) or Low Idle adjustment screws during this abbreviated test procedure.

- Be sure the initial set-up on the governor bench is correct, per the Governor Service Manual, and that the correct calibration pin (1U7316) is being used.The governor bench calibration pin is not the same pin that is used for checking Static Fuel Setting on the engine.

- Do not attempt to check or re-adjust the "Load Stop" setting while performing this abbreviated procedure.The throttle-stop screw (Hi Idle screw) must be loosened and backed out completely when checking and/or adjusting the Load Stop setting.

8. Lower the bench rpm to 1365 rpm, and adjust the Torque Limiter (TORQ LIM ADJ) by turning the screw "in" (CW) to the specification shown below, and record results on the "Governor Calibration Bench - Job & Data Record" page. After adjustment, install the Torque Limiter cover over the adjustment screw.

NOTE: Be sure dial indicator has adequate travel to make the Torque Limiter adjustment. Check by adjusting Torque Limiter adjustment to a larger value first (such as 10.6mm to 10.7mm), then adjusting to the desired value shown above.

9. After TORQ LIM ADJ has been made, release (bleed) the air pressure from the FRC. Check the FRC Adjustment, per Governor Service Manual (SENR6454, October 1994), per topic "Checking Procedure for Previously Adjusted Governors", on page 51, step 8. The FRC specifications for these CH55 governors are listed above in Step 8. Re-adjust the FRC setting only if needed, and then re-check again.

10. Stamp a "T" on the Governor Information Plate in the lower left-hand corner of the plate, just below the words "Lot No.", as shown in Illustration 2.

11. Install lockwire and dealer seal on governor housing; sealing the High Idle screw, the Torque Limiter cover-plug, and Fuel Ratio Control (FRC) cover plug. One lockwire and seal is used to "seal" all these items on the governor. Be sure plastic "seal" does not interfere with governor lever or linkage operation.