BusTekHub Cummins ISL-G Spark Plug Replacement
⇒Engine: Cummins ISL-G
⇒Fuel: CNG / LNG
⇒Rating: 280Hp /320Hp
⇒Spark Plug: Cummins IR-3 4937472 (Cummins Part#4955850) includes spark boot.
⇒Spark plug gap: Pre-gapped from factory, do not adjust
⇒Spark plug torque: 28 ft-lb. (38 Nm.)
⇒Spark plug service interval: Replace every 22,500 mi. (36,000 km.), 1500 Hours or 18 months
Spark Plug: Cummins IR-3 4937472 (Cummins Part#4955850) includes spark boot.
Alcohol pad or swab for cleaning spark plug porcelain.
⇒General socket set, for coil removal.
⇒2 – 5/8 spark plug sockets. One socket to remove old plug, second socket for installing new plug only.
⇒Prior to working on vehicle, turn off batteries or disconnect battery ground.
⇒Wear proper protective equipment.
⇒Follow manufacture’s recommended service and safety procedures.
⇒This instructional article is a supplement to the manufacture’s service procedures.
1. Disconnect coil connectors.
2. Remove coil bracket hold down bolts
3. Remove coil bracket straight up, do not wiggle to remove. Wiggling coil bracket could damage coils. Cylinders 4, 5 and 6.
Removal Cylinders 1, 2 and 3. Pull straight up to clear alternator.
4. Blow out spark plug cavities to prevent debris and dirt from falling into engine cylinder.
5. Remove all spark plugs using spark plug removal socket.
1. Prior to installation spark plug porcelain must be wiped down with alcohol pad or swab. Dirt, oil, and fingerprints reduce the seal strength between the spark plug boot and the porcelain causing reduced spark plug life.
2. Install new spark plug boots to coils, new boots come with dielectric grease from the factory. If boots do not have dielectric grease, apply a small amount.
3. Install new spark plugs using clean install spark plug socket. Do not use removal socket, this will contaminate porcelain on spark plug. Torque spark plug to 28 ft-lb (35 Nm).
Note: Failure to torque spark plugs will result in engine misfire and premature spark plug failure.
4. Install coil brackets and torque to 80 in-lb (9Nm).
5. Inspect coil connector pins for spreading or damage, repair if necessary.
6. Reconnect coils.
7. Turn batteries on or re-connect ground and start engine.
8. Verify no engine misfire and road test vehicle.