Backfires

Definition: Fuel ignites in intake manifold, or in exhaust system, making loud popping noise.

PRELIMINARY CHECKS

^ Perform the careful visual/physical checks as described in DIAGNOSTIC NOTES.

IGNITION SYSTEM

^ CHECK: Proper ignition coil output voltage with spark tester J 26792 or equivalent (ST-125).
^ CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
^ CHECK: Spark plug wires for crossfire, also inspect spark plug wires, and proper routing of plug wires.

IMPORTANT: If an intermittent condition exists in the ignition system, refer to Ignition Systems for further information.

ENGINE MECHANICAL

^ CHECK: Compression - Look for sticking or leaking valves.
^ CHECK: Valve timing.
^ CHECK: Intake and exhaust manifold passages for casting flash.
^ CHECK: Balancer rings for bent or missing vanes.

FUEL SYSTEM

^ CHECK: Perform fuel system diagnosis check, Related Tests, Information and Procedures
^ CHECK: Fuel injectors. Perform injector balance test, Chart C-2A Fuel Injector Balance Test