Centinel System – Repair Manual – 005-054   Stall Speed Test

Stall Speed Check

Time Speed Check

Stall Speed Check List

Stall Speed Too Low

If the Stall Speed is too low, check the following:

1. The tachometer is in error.
   1. Yes
   2. No
2. The engine is up to or above 70°C [160°F].
   1. Yes
   2. No
3. The converter oil is up to 80°C [180°F].
   1. Yes
   2. No
4. The stall has been held long enough for the engine to accelerate to full power.
   1. Yes
   2. No
5. The match curve stall speed was recorded correctly.
   1. Yes
   2. No
6. The converter oil meets the converter manufacturer’s recommendation
   (SAE 30 rather than SAE 10, for instance).
   1. Yes
   2. No
7. The engine-driven accessory power requirements exceed 10 percent of the gross engine power. Check for abnormal accessory horsepower losses such as hydraulic pumps, large fans, oversize compressors, and so on. Either remove the accessory or accurately determine the power requirement and adjust accordingly.
   1. Yes
   2. No
8. The unit is operating at an altitude high enough to affect the engine power.
   1. Yes
   2. No
9. The converter charging pressure is correct.
   1. Yes
   2. No
10. The converter blading is interfering, or in a stage of failure. Check the sump or filter for particles.
    1. Yes
    2. No
11. The converter stators are freewheeling rather than locking up.
    1. Yes
    2. No
12. The engine is set for power other than that specified on the power curve.
    1. Yes
    2. No
13. The converter is wrong due to improper build or rebuild of unit.
    1. Yes
    2. No
14. The converter is performing to the published absorption curve.
    1. Yes
    2. No
15. The engine and converter match is correct. Check the engine and converter models for the proper match.
    1. Yes
    2. No
16. The engine is matched to too large of a converter. If this condition is believed to exist, please report the engine-converter accessory information to the factory.
    1. Yes
    2. No
17. The engine power is down. Perform a cylinder performance test to find the cylinder with low power.
    1. Yes
    2. No

Stall Speed Too High

If the Stall Speed is too high, check the following:

1. The engine is high in power.
   1. Yes
   2. No
2. The tachometer is in error.
   1. Yes
   2. No
3. The accessory power requirements are less than 10 percent of the gross engine power.
   1. Yes
   2. No
4. The converter oil is aerating or foaming. Check for low oil level, air leaks in suction line, lack of foam inhibitor in the oil, or suction screen or filter. Would be accompanied by a noticeable loss of machine performance.
   1. Yes
   2. No
5. The converter is being held at full stall. Check for slipping front disconnect clutch or a rotating output shaft. On the converter-transmission package, this can be impossible to check.
   1. Yes
   2. No
6. The converter turbine element is beginning to fail and lose blades, or the converter was originally built with the wrong size element.
   1. Yes
   2. No
7. The engine and converter match is correct due to a revision in the engine rating or the converter performance.
   1. Yes
   2. No
8. If the oil level is too high on the transmission-converter units with the oil sump in the transmission, it can cause severe aeration due to parts dipping in the oil.
   1. Yes
   2. No
9. The converter is performing to the published absorption curve.
   1. Yes
   2. No
10. The converter charging pressure is correct.
    1. Yes
    2. No

The reasons for abnormal stall speeds listed above are some that have been encountered by Cummins representatives and probably do not
include all possible causes. The correction of the problem is either covered in the vehicle service manual, the converter service manual, or is self-explanatory.