Caterpillar — Ignition System Spark Plugs - Check/Adjust

Maintenance

From a Caterpillar owner's manual covering: 1YG1-Up, 4CG1-Up, G3612, G3616. Check it applies to your exact model before use.

Applies to: Caterpillar G3612, Caterpillar G3616

Procedure

1. Remove spark plug: disconnect wiring harness, remove bolts (2), transformer (3) and gasket (4).
2. Remove extension (5). Remove debris with compressed air (max 207 kPa).
3. Loosen spark plug (6) with 22.23 mm (7/8 inch) spark plug socket and extension. Remove by hand. Discard gasket (7).
4. Inspect spark plug: terminal post must not move; insulator not cracked; shell not damaged; electrode not excessively worn.
5. Measure resistance between terminal post and electrode. Discard if wire-wound resistor outside 1k to 1.5k Ohms.
6. Clean spark plug with glass beads. Do not use wire brush.
7. Set electrode gap to 0.29 ± 0.03 mm (.011 ± 0.001 inch) using 9U-7516 Spark Plug Gauge.
8. Install new gasket (9Y-6792) with tabs toward electrode.
9. Install spark plug by hand until it bottoms out. Tighten to 68 ± 4 N·m (50 ± 3 lb ft).
10. Clean extension connection points. Apply 4C-9504 or 8T-9020 Dielectric Grease.
11. Install extension onto spark plug. Ensure internal spring exerts force.
12. Install transformer. Connect wiring harness. Tighten connector clockwise with pliers.

Source: Caterpillar owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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