Engine Stalling Due To Operating Technique Caterpillar

Engine Stalling Due To Operating Technique

Usage:

BACKHOE LOADERS416C (4ZN, 1WR, 5YN, 1XR),
426C (6XN, 1CR, 1YR, 1MR, 7WN, 1ER, 1ZR, 1NR),
436C (8TN, 1FR, 2AR, 1PR, 9JN, 1GR, 2BR, 1RR),
428C (8RN, 2CR),
438C (9KN, 1JR, 2DR, 1TR) BACKHOE LOADERS

THIS TIB REPLACES THE SEPTEMBER 30, 1998 BACKHOE LOADER TIB, "ENGINE STALLING MAY OCCUR IN SOME OPERATIONAL MODES". DESTROY THE SEPTEMBER 30, 1998 TIB. IT WILL NOT APPEAR IN THE QUARTERLY INDEX.

Problem:

The engine may stall in some operational modes if an incorrect signal pressure is trapped in a pump control valve. This can occur when the operator has one implement in a "STALL" position and another implement is being lowered by gravity. If the operator suddenly releases the control handle for the implement being lowered by gravity, the torque limiter valve will be trapped in a high flow and low pressure position. The pump then sees the high pressure requirement of the stalled implement, but the signal is trapped in the high flow and low pressure position. The engine at low idle cannot produce enough torque to drive the pump at high flow and high pressure requirement, hence the engine stalls.

Solution:

Install a 169-7122 Shuttle Valve between the pump signal line and the pump discharge flange. The shuttle valve selects the lowest pressure. Then it forwards this signal pressure to the pump control system. The pump control system can then "correctly" respond to the occurring condition.

NOTE: Before installing the shuttle valve make sure the pump control circuit is operating properly. This can be tested by performing the tests for the hydraulic pump in SENR1208-01 Systems Operation Testing & Adjusting 416C, 426C, 428C, 436C & 438C Backhoe Loaders Hydraulic & Steering Systems.

NOTE: The 169-7122 Shuttle Valve will not correct other stalling conditions caused by the following:

1. Low idle set below specifications (950 to 1000 RPM).

2. Engines using winter grade fuel.

3. Engine timing improperly set.

4. Fuel setting too low.

5. Hydraulic system pressure set out of specification.

6. The hydraulic pump may require higher than normal torque on engines with less than 50 hours.

7. Engines with 50 to 100 hours that have not been broken in will not produce full torque.

Installation Procedure

NOTE: If the procedure is being performed on an All Wheel Steer Machine skip steps 1 and 2. The hose lengths and hose routing for these machines must be determined.

1. Assemble Hose (12) using 122-6887 Hydraulic Hose, one 124-2140 Hose Coupling, and one 124-2111 Hose Coupling. The overall assembled length is 237 mm (9.33 in). See Illustration 1.

2. Assemble Hose (13) using the 122-6887 Hydraulic Hose, one 124-2140 Hose Coupling, and one 124-2113 Hose Coupling. The overall assembled length is 390 mm (15.35 in). See Illustration 1.

3. Remove floor mat and floor plate to access pump area.

4. Remove one end of the Signal Line (14) from the pump compensator and the existing fitting.

5. Install the 169-7122 Shuttle Valve (1) on the Signal Line (14). See Illustration 2.

6. Install the 7X-2459 Tee to the pump compensator and attach Hose (12).

7. Install Hose (12) onto the 169-7122 Shuttle Valve (1).

8. Replace fitting at the pump discharge flange with the 7X-2459 Tee (2). See Illustration 2.

NOTE: All Wheel Steer machines require the Tee to be mounted to the existing Tee.

9. Install Hose (13) on discharge flange and Shuttle Valve (1).

10. Install Tie Wraps (11) so that the 169-7122 Shuttle Valve is held to the High Pressure Pump Tube or some other position so that the shuttle valve does not move.

11. Check for Boom Stall Condition. Machine should be at low idle (950RPM).

Reference: SEBU6873 Operation & Maintenance Manual 416C, 426C, 436C, 428C, & 438C Backhoe Loaders. See Operation Section, Attachment Controls.

a. Install the boom transport lock.

b. Move the necessary lever to move the stick out. Extend the stick out fully.

c. Move the necessary lever to move the boom down.

d. While holding the boom down lever down, move the necessary lever to bring the stick in. Perform this quickly to about half way. Then release the stick in lever.

The machine should not stall.

12. Replace floor plate and mat.

Illustration 1.