M11 Series – Service Manual – 005-054   Stall Speed Test

Converter Transmissions Stall Speed

The stall speed is the engine speed (rpm) obtained at full throttle when the converter output shaft is locked.

NOTE: It is possible the vehicle brakes will

not hold an electronically controlled transmission.

The following equipment is needed for this check:

• Stop watch
• Digital tachometer kit, Part No. 3375631, or optical tachometer, Part No. 3377462
• Equipment manufacturer’s stall speed and time to stall specifications

Install the tachometer on the fuel pump.

Place the gear selector in the highest gear or full forward.

Make sure the vehicle has good brakes and air pressure in the brake system.

NOTE: The brakes

must
prevent the vehicle from moving when the engine is at full throttle. Engage the vehicle brakes to keep the vehicle from moving.

Operate the engine until the converter temperature is 80°C [180°F]
or above.

Bring the engine speed back to low idle.

CAUTION  Do not exceed 120°C [250°F] converter oil temperature. Overheating and damage to the converter can occur.

Quickly move the throttle to the full open position.

Check the engine speed (rpm) at the point of stall:

• Always hold the speed until it is stable
• Take several readings
• Make sure the readings are accurate

Check the speed (rpm) against the specifications for the equipment, converter, or automatic transmission.

NOTE: The stall speed for the engine and converter/transmission can vary ±
8 percent from the manufacturer’s specifications.

If the stall speed is

not
within the specifications, refer to the stall speed check list at the end of this section.

Check the equipment manufacturer’s troubleshooting procedures for other reasons for stall speed problems.

Adjust the throttle shaft plunger screw, if necessary, to change the stall speed. Refer to Procedure

005-028.

NOTE: Do

not
increase the fuel rate unless it is the true cause for the low stall speed. Overfueling of the engine and poor durability can result.

Perform the previous Stall Speed Check procedure through the “check the engine speed (rpm) at the point of stall” step then:

• Quickly move the throttle to the full open position and start the stop watch at the same time

• When the engine speed is 90 percent of the stall speed rpm, stop the stop watch

Example: Stall speed 2089, [2089 X .90 = 1880 rpm]

NOTE: The type of unit and the stall speed rpm can make the stall speed time a maximum of 10 seconds.

Check the equipment manufacturer’s specifications for the time to stall or the acceleration time.

If the time is excessive, check the fuel pump AFC for an air leak. Refer to Procedure

006-047 and the Stall Speed Check List at the end of this procedure.