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HOMESERVICE MANUALSCHEVROLET1998SUBURBAN K2500, 7.4 J, PART TIMEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 337 (ENGINE CONTROLS TROUBLESHOOTING - NO CODES - 3.1L)SYMPTOMSENGINE BACKFIRESIGNITION SYSTEM
1998 Chevrolet Suburban K2500, 7.4 J, Part Time

Ignition System

1998 Chevrolet Suburban K2500, 7.4 J, Part TimeSECTION Ignition System
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

Check the spark plugs for proper heat range and reach. See IGNITION SYSTEM SPECIFICATIONS in appropriate SERVICE & ADJUSTMENT SPECIFICATIONS article. Check for proper ignition voltage output using the following steps:

  1. Attach Spark Tester (J 26792) to engine ground.
  2. Connect the spark plug end of the spark plug wire to the spark tester. Connect the other end of the spark plug wire to the coil being tested.
  3. Connect the spark plug end of the companion spark plug wire to ground. The companion spark plug wire is the wire attached to the corresponding coil tower.
  4. Crank the engine while observing the spark tester. A spark should be observed.
  5. Repeat steps  1 - 4 for each coil.

If spark is not present at the coils, check for the following conditions:

  1. Coils  - Cracks, carbon tracking/arcing, or a resistance value outside 5-8 k/ohms.
  2. Spark Plug Wires  - Signs of arcing, cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside 3000 ohms per foot (9868 ohms per meter). Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. Ignition voltage arcs to ground when a secondary component is faulty.
  3. Defective Ignition Module  - See ELECTRONIC IGNITION SYSTEM DIAGNOSIS under IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.
  4. Ignition System Wiring  - Loose ignition module feed or ground connection, or damaged system wiring.

Remove spark plugs and check for the following conditions:

  • Fouled plugs.
  • Cracks.
  • Wear.
  • Improper gap.
  • Burned or damaged electrodes.
  • Improper heat range or reach.

If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.