MSD 8739 Two Step Module Selector Instruction Manual

Product Overview

The MSD 8739 Two Step Module Selector is designed to provide precise RPM control for automotive ignition systems. It allows users to switch between two distinct RPM or timing retard modules, enhancing vehicle performance and control, particularly in racing applications. This unit is intended for use with MSD Soft Touch Rev Controls or MSD Timing Computers.

Image: The MSD 8739 Two Step Module Selector, a compact electronic device with wiring terminals.

What's Included

• MSD 8739 Two-Step Module Selector

Setup and Installation

The MSD 8739 Two Step Module Selector requires connection to an existing MSD Soft Touch Rev Control or MSD Timing Computer. Professional installation is recommended.

Wiring Connections:

Refer to the wiring diagram provided with your MSD Soft Touch Rev Control or Timing Computer for specific connection points. The 8739 unit typically connects to the module input terminals of the main ignition control unit.

• Power: Ensure the ignition system is off before making any connections.
• Module Selection: The 8739 unit facilitates switching between two RPM modules (not included). Insert the desired RPM modules into the designated slots on the 8739 selector.
• Activation Switch: Connect an external switch (e.g., a clutch switch or transbrake switch) to the 8739 unit to activate the second RPM limit.

Note: RPM Modules are sold separately and are not included with the 8739 Two Step Module Selector.

Operating Instructions

The MSD 8739 Two Step Module Selector allows for two distinct RPM limits to be used. One RPM limit is active by default, and the second RPM limit is activated via an external switch.

Setting RPM Limits:

1. Install the desired RPM modules into the 8739 selector. For example, a lower RPM module for launch control and a higher RPM module for general engine protection.
2. Ensure the 8739 unit is correctly wired to your MSD ignition control and the activation switch.

Using the Two Step Function:

When the activation switch (e.g., clutch pedal depressed, transbrake engaged) is active, the 8739 unit will engage the RPM limit of the second module. Releasing the switch will revert to the RPM limit of the first module.

This functionality is commonly used for consistent launch RPMs in drag racing or other performance applications.

Maintenance

The MSD 8739 Two Step Module Selector is a solid-state electronic device and requires minimal maintenance.

• Inspection: Periodically inspect all wiring connections for tightness and signs of wear or corrosion.
• Cleaning: Keep the unit clean and free from excessive dirt, moisture, and extreme temperatures. Use a dry, soft cloth for cleaning.
• Module Care: Handle RPM modules carefully. Ensure they are seated correctly in the selector.

Troubleshooting

If you experience issues with your MSD 8739 Two Step Module Selector, consider the following:

• No Second RPM Limit:
  • Check all wiring connections, especially the activation switch. Ensure the switch is functioning correctly.
  • Verify that the RPM modules are correctly inserted and are the correct type for your application.
  • Confirm that your MSD ignition control unit is compatible with the 8739 selector.
• Incorrect RPM Limit:
  • Ensure the correct RPM modules are installed for the desired limits.
  • Check for any loose connections that might cause intermittent signals.
• Unit Not Functioning:
  • Verify power supply to the MSD ignition control unit.
  • Inspect for any visible damage to the 8739 unit or its wiring.

For further assistance, contact MSD technical support.

Specifications

Warranty Information

This product is covered by a manufacturer's warranty. For specific details regarding warranty coverage, duration, and claims process, please refer to the documentation included with your purchase or visit the official MSD website.

Warranty Description: Warranty

Safety Information and Warnings

CALIFORNIA WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

Always disconnect the vehicle's battery before installing or servicing any electrical components.

Ensure all wiring is properly insulated and secured to prevent short circuits or electrical hazards.

Installation should be performed by qualified personnel to avoid damage to the product or vehicle.

Support

For technical assistance, product inquiries, or troubleshooting support, please contact MSD customer service.

MSD Official Website: www.msdperformance.com

Please have your product model number (8739) and purchase information ready when contacting support.