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Dodge Ram 2002-2008: How to Replace Ignition Coils and Spark Plugs

Spark plugs ignite the air/fuel mixture in the combustion chamber by creating a spark when commanded by the engine computer. Over time, the gap between the spark plug electrodes increases to the point that the spark will no longer jump the electrode gap, requiring their replacement.

By Weston Chadwick - July 14, 2015

This article applies to the Dodge Ram 3rd Generation (2002-2008).

The Dodge Ram uses several different engines in its third generation model years. The 3.7 liter V6 and 4.7 liter V8 removal procedures are similar. The 5.7 liter Hemi uses two spark plugs per cylinder with one plug attached to the coil pack and the other attached to a spark plug wire boot. The Hemi incorporates this design for better combustion efficiency and lower emissions.

Many different types of spark plugs are available for these engines. Copper electrode plugs are used from the factory on these engines with a maintenance interval of 30,000 miles. Some owners have used platinum and iridium plugs with success for the increased maintenance interval accompanied with that type of plug. Be sure the gap is set correctly out of the box, otherwise poor fuel economy and misfires may result. If for any reason the set gap is lost, the plugs should be at 0.040"

Materials Needed

  • 6, 8, or 16 spark plugs
  • Spark plug gapping tool
  • Anti-seize
  • 3/8" and/or 1/2" ratchet
  • Swivel adapter
  • 3" and 5" extensions
  • 10mm socket
  • 5/8" spark plug socket
  • Flat head screwdriver

Step 1 – Remove the resonator box

Connected to the passenger's side of the resonator box is an intake pipe. It is held onto the resonator box with a hose clamp. Use either a flat head screwdriver or an 8mm socket to loosen the clamp and pull the pipe off of the resonator box.

Now remove the two 10mm bolts holding the air box to the engine. These are located at both sides of the resonator box. The bolt on the passenger's side is behind the alternator. The bolt on the driver's side can be found behind the oil filler cap.

Once these bolts are removed, carefully lift the resonator box high enough to access the sensor located at the front of the resonator box. Squeeze the tab on the connector plug while pulling the plug away from the resonator box. You can now fully remove the resonator box from the engine.

The 4.7 liter has two bolts located on each side of the resonator box. The bolt on the passenger's side is below the intake pipe elbow. On the backside of the box is a crankcase vent hose that is easily removed by pulling it off of the box. Before removing the box completely, make sure you have disconnected the air intake temperature sensor.

To remove the resonator box on the 3.7 liter, depress the locking tab holding the electrical connector to the air temperature sensor while pulling it away from the resonator box. This sensor is located on the backside of the resonator box near where the intake pipe mounts. Then, remove the two 10mm bolts at each side of the box. Pull up on the box to release it from the engine, but do not remove it from the engine bay. On the backside of the box is a crankcase vent hose that needs to be removed. The layout will be similar to the 4.7 engine. Figures 1 through 4 are the different ways to remove the resonator box depending on the engine variation.

Figure 1. The circles represent the hose clamp and 10mm bolt locations for the 5.7.

Two bolts will need to be removed on the left and right side from the 4.7 liter engine.

  • Figure 2. One of the bolts found on the 4.7 liter resonator box.
  • Figure 3. The second bolt holding the 4.7 resonator box in place.

Lastly, Figure 4 shows the 3.7 liter model with the places to remove the bolts.

Figure 4. The red arrows point to the locations of the two 10mm bolts on the 3.7 liter.

Step 2 – Remove the coil packs

The 5.7 liter Hemi engine has 16 spark plugs, with eight of the plugs covered by normal spark plug wire boots and the other eight by coil packs. Remove the spark plug wire boots by twisting them slightly, then pull them upwards. You will hear them pop as they break free. To remove the coil packs, first disconnect the electrical connector plug. Slide the red tab on the connector to the unlock position and squeeze down on the locking tab while pulling the plug away from the coil pack. The only thing holding the coil packs in place now are the two 10mm bolts.

The differences between the Hemi and 4.7/3.7 liter engines is that there are only coil packs on the smaller engines. Also, there is only one 10mm bolt holding the coil pack to the engine.

  • Figure 5. One of the coilpacks and plug wires have been removed on the 5.7 Hemi.
  • Figure 6. The red circle indicates one of the eight coil packs on the 4.7 liter engine.
  • Figure 7. Another view of the coil packs positioning on the 4.7 and 3.7 liter engines.

Step 3 – Remove the spark plugs

Carefully turn each spark plug counterclockwise until they are removed. Once they are loose enough, use your hand to twist them out with the extension to reduce the chance of thread damage.

Figure 8. All 16 spark plugs removed from the 5.7 Hemi.

Step 4 – Install the new spark plugs, coil packs, and resonator box

Check that the new spark plug is gapped correctly at 0.040".

Apply a small amount of anti-seize onto the spark plugs threads. Start threading the spark plugs into the hole by hand with an extension and torque to 15 ft. lbs.

Slide the coil packs spark plug boot wires onto the top of the spark plugs. You will feel them press against the top of the plug when they are positioned correctly. Tighten the coil pack bolts to 70 in. lb or 5 ft. lb. Re-connect the electrical connector plugs to the coil packs.

Now re-install the resonator box. Remember on the 3.7 and 4.7 liter engines there is a crankcase ventilation hose that needs to be re-attached on the back side. Tighten the box down with the two 10mm bolts and slide the air intake pipe back onto the box. Now secure the pipe to the box with the clamp and you are finished with the install!

Figure 9. With your combustion problems solved, your Ram is good to go.

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