Mazda RX-8 S1 Oil Metering Pump Guide

The Mazda RX-8 Series 1 Renesis engine uses an Oil Metering Pump, usually shortened to OMP, to inject small, controlled amounts of oil into the rotary engine for internal seal and housing lubrication.

This guide focuses only on the Series 1 RX-8 OMP system, fitted to the earlier RX-8 generation. It does not cover the later Series 2/R3 system, which uses a different oil metering arrangement.

The Series 1 system uses a single electronically controlled metering oil pump. The PCM controls the pump through a stepping motor strategy, using engine operating conditions to decide how much oil should be delivered.

Unlike a conventional piston engine, the Renesis rotary engine has apex seals, side seals and corner seals moving against the rotor housings and side housings. These contact surfaces need a controlled oil film to reduce wear and help maintain sealing. Because of this, some engine oil consumption is normal on a standard RX-8.

Important note: This guide is not a replacement for the Mazda workshop manual. Exact torque values, connector diagrams, part numbers and procedures should be confirmed against the correct service information for the exact model year.

Guide sections

1. How the RX-8 Renesis OMP works

This section explains the purpose of the OMP, why the rotary engine needs oil injection, and how the Series 1 stepper-motor OMP system delivers oil to the engine.

Topics covered:

• What the OMP does
• Why the Renesis consumes oil
• Why rotary engines need injected oil
• Series 1 OMP system layout
• Oil flow from sump oil to rotor housing
• PCM stepper-motor control
• OMP position switch and learning function
• Main components and their roles
• Common system failure modes

2. OMP diagnostics and testing

This section covers practical checks for diagnosing OMP problems. It includes visual inspection, voltage testing, resistance testing, position switch checks, oil nozzle testing, leakage checks and clogging checks.

Topics covered:

• Pre-diagnostic checks
• Oil level and oil condition
• Warning signs and symptoms
• OBD-II fault code checks
• OMP voltage inspection
• OMP resistance inspection
• Position switch resistance inspection
• Oil nozzle vacuum testing
• Oil leakage inspection
• Oil pipe and connector bolt clogging checks
• Test result templates

3. OMP removal, installation and servicing

This section covers how to approach removing, inspecting and reinstalling the Series 1 OMP safely. It also discusses what can realistically be serviced and what should normally be replaced.

Topics covered:

• Required tools
• Required seals and washers
• Safety precautions
• Access preparation
• Labelling oil lines
• OMP removal
• OMP inspection after removal
• Oil line inspection
• Rebuild vs replacement decision
• Installation
• Priming
• First start and leak checks
• Post-service checks

4. Oil nozzles, premix and clean oil feed systems

This section focuses on the parts around the OMP: oil nozzles, oil lines, premixing two-stroke oil, and clean oil feed / SOHN-style modifications.

Topics covered:

• Series 1 oil nozzle function
• Oil nozzle removal and testing
• Blocked nozzle symptoms
• Oil line restrictions
• Premix theory
• Why premix does not repair a failed OMP
• Clean oil feed systems
• Risks and trade-offs
• Maintenance checks after modification