2009 Ram 1500 5.7 HEMI Spark Plug Gap and Plug Count

The documented 2009 HEMI application

Ram's 2009 1500 manual lists the NGK LZFR5C-11 at 0.043 in (1.09 mm) for the covered 5.7L HEMI. This is a reliable model-year reference, not a universal statement about every later HEMI generation or every superseding Mopar plug.

The 5.7L uses two plugs per cylinder, so a complete service contains 16 correctly matched plugs. Keep removed plugs organized by cylinder and upper/lower location; mixing evidence makes it harder to trace oil fouling, coolant contamination, or one-cylinder ignition faults.

Sixteen-plug planning and inspection

Work on a cool aluminum head, clean around every plug well, disconnect coils carefully, and start each replacement by hand. Inspect boots and spring contacts while access is open, because a torn boot or carbon track can reproduce a misfire even with new plugs.

Later Ram manuals may specify only an approved Mopar part and maintenance interval. For those trucks, use the VIN-cataloged replacement and current service information rather than forcing the 2009 plug number or modifying a modern preset electrode.

Choosing the correct 1500 5.7L HEMI row

A specific Mopar model-year source supports the 0.043-inch answer without presenting it as a universal figure for every 5.7L HEMI revision. Match model year, engine code, emissions label, and the approved plug number. Where the table shows a range, a clean wire gauge should pass with light, even drag without scraping the precious-metal tip.

Do not mix plug part numbers, lose the removed positions, or aggressively bend a preset fine-wire electrode. Modified boost, non-stock cylinder pressure, or an aftermarket calibration may have builder instructions, but a smaller internet-recommended gap is not a repair for weak coils, damaged boots, or fueling problems.

Spark-plug gap chart for 1500 5.7L HEMI

A specific Mopar model-year source supports the 0.043-inch answer without presenting it as a universal figure for every 5.7L HEMI revision. The range NGK LZFR5C-11 applies only to the row where it appears. Production changes can occur inside a generation, and performance packages may use a different plug or gap from the standard engine. The under-hood emissions label, VIN-filtered parts catalog, and exact owner/service manual take priority over a broad web lookup.

Record both inch and millimeter values to avoid conversion mistakes. One millimeter equals 0.03937 inch, so a casual decimal rounding can move a plug outside a narrow published range. Use a gauge marked in the unit shown by the source and check calibration if the tool is worn, bent, or difficult to read.

Why the correct plug part number matters

Gap is only one dimension. Thread diameter and reach determine whether the plug fits the head and positions the electrode correctly. Seat style determines how it seals and how torque creates clamping force. Heat range controls how quickly the insulator transfers heat, while resistor and electrode design affect ignition and electromagnetic compatibility. Substituting by gap alone can damage the engine.

Do not mix plug part numbers, lose the removed positions, or aggressively bend a preset fine-wire electrode. Cross-reference catalogs are useful, but confirm the final selection against the VIN, engine code, emissions label, or manufacturer catalog. Do not assume every plug in a multi-pack is identical; inspect the printed number and physical condition of each one.

How to measure a fine-wire plug safely

Use a round wire gauge that fits between the electrodes without forcing them apart. A flat blade can bridge curved surfaces and give a misleading result. Insert the wire gently at the open side of the gap. It should pass with light, even drag. Do not scrape an iridium or platinum tip repeatedly, and never press a tool against the center electrode or insulator nose.

If adjustment is allowed, move only the ground strap with a purpose-made tool and make tiny corrections. Keep the ground strap centered over the center electrode and parallel at the measurement point. If the strap is twisted, the weld is stressed, the porcelain is chipped, or the gap changes with light pressure, discard the plug.

Installation torque and thread protection

Plug torque depends on thread size, seat type, gasket condition, cylinder-head material, and whether the plug is new or reused. Use the exact engine procedure. Too little torque can impair heat transfer and allow combustion leakage; too much can distort the shell, damage the insulator, or strip aluminum head threads. Start every plug by hand with the socket and extension only.

Many modern plugs have a plated shell designed for installation without anti-seize. Adding compound changes friction and can cause over-tightening at the specified wrench value. Apply lubricant only when the vehicle or plug manufacturer explicitly directs it and provides the corresponding torque method. Keep dielectric grease, if specified, inside the boot—not on the electrical terminal or plug threads.

What plug condition can reveal

• Dry black deposits can accompany rich operation, weak ignition, excessive idling, or an unsuitable heat range.
• Wet fuel after repeated cranking suggests the cylinder is not firing or the engine is flooded.
• Oily deposits can point to oil control, guide, turbocharger, or crankcase-ventilation problems.
• A white, blistered, or eroded insulator/electrode can indicate overheating, detonation, lean operation, or the wrong plug.
• A cracked insulator or carbon track can cause a load-dependent misfire even when the gap looks correct.
• Uneven condition across cylinders is a reason to diagnose that cylinder rather than simply fitting a hotter plug.

Diagnosing a misfire after plug replacement

If a misfire appears immediately after service, first recheck connector engagement, coil seating, boot springs, plug part numbers, gap, and torque. Look for a cracked porcelain caused by a tilted socket. Confirm that no vacuum hose, ground, or harness was left disconnected. Moving a coil or plug to another cylinder can help isolate a component only when the diagnostic procedure permits it.

The engine uses 16 plugs—two per cylinder—so part consistency, position tracking, cool-head installation, and coil-boot inspection are essential. Do not shrink the gap below the manufacturer range to conceal a weak coil, fueling error, excessive boost, or mechanical problem. That may suppress one symptom while reducing combustion quality and delaying the real repair.

Procedures used with this specification

These steps are the same for every vehicle in this family, so they are documented once rather than repeated on each page. The values above remain specific to this Ram 1500 5.7L HEMI.