TOPIC: Fuel System
IDENT NO: 9-4130
DATE: August 2020
275GL+* SUPERSEDES: NEW
SUBJECT: Loose Stepper Motor
MODELS AFFECTED: 12V 275GL+ and 16V 275GL+
The purpose of this bulletin is to inform the field To inspect the installation of the stepper motor,
that the stepper motor, P/N AC740502E, on 12V remove the stepper motor harness. Check to
275GL+ and 16V 275GL+ engines may become see if the stepper motor is loose. If the stepper
loose. RPM variation and poor gas control are motor is loose, remove the stepper motor from
symptoms of a loose stepper motor. If you have the fuel regulator. Check the lead threads of the
an engine experiencing these symptoms, at the motor:
first opportunity, stop the engine and inspect
• If the lead threads are broken, the stepper
the installation of the stepper motor.
motor will need to be replaced. Order
P/N AC740502E.
! WARNING • If the lead threads are not broken, the original
Allow the engine to cool to room stepper motor can be reused.
temperature before cleaning, NOTE: When installing the stepper motor,
servicing and repairing the unit. discard the two original washers and replace
Be sure the fuel supply to the them with two new copper washers, P/N 290029.
engine has been shut off before Loctite® 567™ sealant will also be needed.
servicing the fuel system.
To install the stepper motor:
Always wear protective
equipment when servicing the 1. Be sure the male and female threads are
fuel system. clean.
2. Position the new copper washers, P/N 290029,
and the original spacer onto the stepper
motor, orienting them as shown in Figure 1.
* Trademark of INNIO Waukesha Gas Engines, Inc.
All other trademarks are the property of their respective owners.
08/3/2020
Copyright © 2020, INNIO Waukesha Gas Engines, Inc. Page 1 of 2
Service Bulletin No. 9-4130
Optional: Mark the threads vertically with a paint
pen. This can be checked periodically to ensure
that threads have held tight and stepper is in
alignment. See Figure 2 for an example.
Figure 2: Vertical Mark on Stepper Threads
Figure 1
1 - Copper Washers, 2 - Original Spacer
P/N 290029
3. Apply a thin layer of Loctite 567 sealant
around the male threads.
4. Thread the stepper in place by hand until
tight.
5. Using a chain wrench, tighten the stepper
motor to 90 ft-lb (122 N·m).
6. Remove excess Loctite sealant.
7. Reconnect the stepper motor harness.
NOTE: Allow the sealant to dry for
10 minutes.
08/3/2020
Copyright © 2020, INNIO Waukesha Gas Engines, Inc. Page 2 of 2
