This guide provides step-by-step instructions for setting the timing on a DS4 injection pump using a scan tool with TIME SET and TDCO Learn capabilities.

• Scan tool (TECH II recommended)

• Basic hand tools for pump adjustment

1. Access the "Time Set" feature on your scan tool

2. Adjust the pump position until the "Actual Timing" reading averages approximately 3.5

   • Note: Some fluctuation in the reading is normal

Important Note for Advanced Users: While experienced technicians may skip the TIME SET command, novice users should always perform this step to ensure accurate positioning.

1. Perform a "TDCO Learn" procedure

2. Record the resulting TDCO (Top Dead Center Offset) value

1. Make small incremental adjustments to the pump position

2. Perform TDCO Learn after each adjustment

3. Continue adjusting until reaching desired specifications:

   • Factory setting: -0.50

   • Acceptable range: -0.25 to -0.75

1. Verify final TDCO value is within specification

2. Tighten all three pump retaining nuts to proper torque specification

If TDCO Learn returns the following values:

• OBDI: -1.94/+1.94

• OBDII: -2.46/+2.46

These readings indicate either:

1. The pump position needs to be reset using the Time Set feature (return to Step 1)

2. A potential mechanical issue exists that requires investigation

• A TECH II scan tool is strongly recommended for this procedure

• Not all scan tools support the TIME SET function, which may complicate the timing process

• The TIME SET feature significantly reduces the time required for accurate pump positioning