Volvo Penta Ignition Coil 3859078

Volvo Penta OEM Ignition Coil – Part No. 3859078

Compatible Applications

Ignition coil configurations can vary by engine version and serial-number range. Confirm 3859078 against the Volvo Penta ignition diagram and engine serial number before ordering.

• Volvo Penta 8.1Gi-C / D / E / F / G / H and related variants
• Volvo Penta 8.1GiE / 8.1GiI family variants
• Volvo Penta 8.1GXi-B / C and related variants
• Selected additional 8.1L Volvo Penta V8 gasoline engine configurations — verify by serial number

Symptoms of a Failing Ignition Coil

Diagnose the ignition system before replacing coils. A single failed coil typically causes a single-cylinder misfire; replacing all eight at once may be appropriate for high-hour engines. Common symptoms include:

• Rough running or engine vibration at idle or under load
• Single-cylinder misfire or dead cylinder
• Loss of power or fuel economy
• Misfire fault codes from the ECM
• Intermittent ignition dropout that worsens when warm

Service Interval

Volvo Penta does not specify a fixed coil replacement interval for 3859078. Replace when a coil tests faulty, when misfire symptoms are diagnosed to a specific cylinder, or as a complete set on high-hour engines during a full ignition service. Inspect coil boots and connectors at each annual service.

Installation Notes

Each coil installs directly onto the spark plug (coil-on-plug arrangement) — 8 coils are required for a full engine set. Before installation, inspect the spark plug, coil boot, and wiring connector for each cylinder. A failed coil boot can cause arcing and misfire even with a new coil. Follow the Volvo Penta service procedure for the 8.1L ignition system and clear any ECM fault codes after replacement to confirm the repair.

Technical FAQ

Do I need to replace all 8 coils at once?
Not necessarily — if diagnosis confirms a single failed coil, replacing only that coil is acceptable. However, on high-hour engines where the coils have significant service time, replacing the full set avoids successive single-coil failures in quick succession. Many technicians replace all eight during a major service interval.

How do I identify which coil is failing?
An ECM scanner will typically show which cylinder is misfiring. Swapping the suspected coil with an adjacent cylinder and checking whether the misfire follows the coil is a reliable field test. The misfire code cylinder number corresponds to the coil position.

Is R117012 a direct OEM replacement?
R117012 is listed as a cross-reference for this application. Use 3859078 as the primary Volvo Penta OEM ordering number. Verify any cross-reference against your exact engine model and serial number before use.

What spark plugs are used with this coil?
Confirm the correct spark plug specification for the 8.1L engine in the Volvo Penta service documentation. The plug and coil boot condition both affect coil performance and service life.

Parts Desk Insights

This coil comes up most during misfire diagnostics on 8.1L V8 engines — it’s the most common ignition-related repair on this platform. The most frequent ordering question is whether to replace one or all eight; for engines with substantial hours, replacing the full set during the same service call is the most cost-effective approach and eliminates the repeat callback risk. Coil boot condition is worth checking at the same time — a cracked or corroded boot will cause arcing and a misfire even with a new coil installed.