GM 12563554
Glow Plug

Users must verify the installation of an appropriate Spark Plug since improperly fitted spark plugs can cause driveability problems and they should consult ignition system specifications to identify the correct plug type. The correct heat range for the Spark Plug is vital because choosing an incorrect heat level could result in fouling damage or pre-ignition that risks harming the engine. Check the terminal post for damage and verify its straightness before performing a stability test by twisting and pulling motion which should result in no movement. The insulator should be scanned for flashover and carbon tracking events because electric charges may bridge between terminal post and ground while boot damage and recess area moisture needs assessment to prevent arcing. Check the insulator for cracks that could allow improper electrical charge arcing and measure the center electrode distance from the side electrode to verify normal Spark Plug functioning range. A Spark Plug operating correctly requires proper torque that must be confirmed because improper torque levels cause operational failure although excessive torque may break the insulator. The presence of tracking near the insulator tip should be checked while performing a thorough examination of the side electrode for damage and wear and the center electrode for looseness or physical damage which produces a rattling sound. Check to see if there are deposits causing bridged (3,4) electrodes while inspecting for lateral damage and excessive fouling on platinum pads if electrodes (3,4) possess platinum features. Dry all debris and refuse from the Cylinder Head Spark Plug recess since improper thread conditions will block proper installation seating. The normal Spark Plug condition presents brown to grayish-tan coloration with minute white powder formations yet carbon fouling surfaces as dry fluffy black carbon because of rich fuel mixtures, leaking fuel injectors or excessive fuel pressure or restricted air filters or combustion issues. Different causes of fouling include low ignition system voltage together with weak coils and worn wires and Spark Plug gaps that are improperly set-up as well as extended idling or sluggish vehicle speeds that stop normal combustive residue from disappearing. The formation of glaze on the electrode by oil deposits alongside coolant or additives may seriously decrease spark intensity.

Every Spark Plug installation must use the proper plug model since improper ones lead to driveability problems. An ideal heat range in the Spark Plug is crucial because both temperature extremes have different side effects which impact plug and engine health. Examine the terminal post for damage followed by a check for breakage and bending and perform a twisting and pulling movement to verify its stationary position. An inspection of the insulator between terminal post and ground must check for flashover and carbon tracking phenomena that allow electrical charge to travel across the insulator . Check the Spark Plug boot for damage and examine the Cylinder Head Spark Plug recess to determine if moisture has saturated the boot because water in a boot can create ground arcing. There should be no crack detected on the insulator because such cracks allow electrical charge to arc instead of reaching the electrodes (3, 4). A measurement of the center electrode gap to the side electrode gap must match ignition system specifications because extended spacing impedes Spark Plug performance. The correct torque for spark plugs should be verified per ignition system specifications because poor torque can produce operational failures but excessive torque might damage the insulator through cracking. Before the center electrode check for tracking signs near the insulator while performing a shaking test for both side and center electrodes to detect internal damage and ensure spark intensity. Check the electrodes (3, 4) for bridging from deposits which can seal the gap and examine the electrodes (3, 4) for platinum pad wear and absence if such pads exist. Excessive fouling should be checked during inspection together with ensuring the Cylinder Head's Spark Plug recess area remains clean of debris to permit proper seating when installing the spark plugs. The normal operational Spark Plug reveals a brown to grayish-tan coloration with limited white powder but carbon fouling develops into dry black sooty carbon particles resulting from fuel-rich mixtures, fuel injector leaks and high fuel pressure levels or restricted air filters and improper combustion and insufficient ignition system voltage and weak ignition coils. Spark intensity suffers from reduced performance due to two main factors: excessive idling alongside slow speeds under light loads and deposit fouling through oil, coolant or additive contamination. Although most powdery deposits will not affect spark intensity before glazing occurs.

For removing spark plugs, disconnect the Spark Plug Wires; choose the Spark Plug wire harness replacement (5.0L-5.7L) for spark plugs and Spark Plug wire harness replacement (7.4L) for those with a 7.4l engine. Loose the spark plugs a few turns because they work best when removed from the wells. Brush off dirt from around the spark plugs and afterward, take the spark plugs out one by one, putting them into a tray matching their cylinder numbers. While installing, fit every Spark Plug washer in the right place and check the gap of the Spark Plug, changing it to match the correct specification which is 1.524 mm (0.060 in). For tightening the bolts, use 15 n.m (11 lb ft) for iron head installations of 4.3l, 5.0l and 5.7l, 20 n.m (15 lb ft) for iron head installations of 7.4l and 30 n.m (22 lb ft) for iron heads newer than those offered in 4.3l, 5.0l, 5.7l and 7.4l. After finishing the rebuild, put the Spark Plug Wires back and use the Spark Plug wire harness replacement (5.0L, 5.7L) for 5.0/5.7l models and the Spark Plug wire harness replacement (7.4L) for 7.4l engines.

Start by taking off the Spark Plug Wires and very slightly loosen each Spark Plug with 1 or 2 rotations. Cleansing the Spark Plug areas with a brush or air blower enables safe removal of each Spark Plug for placement into labeled cylinder-trays. Set each Spark Plug washer correctly and check or adjust its gap to achieve the correct measurement of 1.524 mm (0.060 in). The technician should begin hand-tightening spark plugs to specific torques of 15 n.m (11 lb ft) when using used heads and 30 n.m (22 lb ft) using new iron heads while new aluminum heads require a torque setting at 20 n.m (15 lb ft). Finish the process by reinstalling Spark Plug Wires.

For removing spark plugs, disconnect the Spark Plug Wires; choose the Spark Plug wire harness replacement (5.0L-5.7L) for spark plugs and Spark Plug wire harness replacement (7.4L) for those with a 7.4l engine. Loose the spark plugs a few turns because they work best when removed from the wells. Brush off dirt from around the spark plugs and afterward, take the spark plugs out one by one, putting them into a tray matching their cylinder numbers. While installing, fit every Spark Plug washer in the right place and check the gap of the Spark Plug, changing it to match the correct specification which is 1.524 mm (0.060 in). For tightening the bolts, use 15 n.m (11 lb ft) for iron head installations of 4.3l, 5.0l and 5.7l, 20 n.m (15 lb ft) for iron head installations of 7.4l and 30 n.m (22 lb ft) for iron heads newer than those offered in 4.3l, 5.0l, 5.7l and 7.4l. After finishing the rebuild, put the Spark Plug Wires back and use the Spark Plug wire harness replacement (5.0L, 5.7L) for 5.0/5.7l models and the Spark Plug wire harness replacement (7.4L) for 7.4l engines.

Choose the right Spark Plug since a wrong Spark Plug will lead to driveability problems. The heat range of the Spark Plug needs precise selection because a cold plug can become fouled while a heated plug can start ignition early leading to Spark Plug failure or engine harm. The terminal post must be inspected for damage then checked for free movement by twisting and pulling until it stops. It should not bend or break during this test. The insulator needs evaluation for flashover or carbon tracking because electric charge can move between terminal post and ground along this area. Check for boot damage on the Spark Plug and check for moisture in both the Spark Plug recess on the Cylinder Head and boot area because boot saturation results in ground arcing. Check the insulator for any existing cracks because such defects can enable electrical charge to perform arcing instead of contacting the electrodes (3, 4). Inspection of the space between center electrode and side electrode must be conducted to meet ignition system specifications as a large gap can reduce Spark Plug efficiency. The Spark Plug torque must match the ignition system specifications because torque under the specified values can trigger operational faults but excessive torque might result in insulator cracking. Warning signs of tracking should be inspected near the tip of the insulator instead of the center electrode . Check for internal damage and increased spark intensity by shaking the Spark Plug; both broken or worn side electrode and center electrode should be easily felt through this technique. Check for bridged electrodes (3,4) as well as investigate worn or missing platinum pads on electrodes (3,4) with applicable tests and determine excessive fouling amounts. The installation process will be compromised by debris in the Spark Plug recess area of the Cylinder Head because dirty threads may impede proper seating. The Spark Plug characteristics of normal operation include a brown to grayish-tan color with small white powdery deposits but when fouled with carbon it displays dry black sooty deposits because of rich fuel mixtures and different fuel and air filter issues and ignition limitations. The spark intensity decreases because of deposit fouling that comes from oil and coolant together with additives where a glaze can develop atop the electrode.

Clean any dirt around the spark plugs using a brush or air blast.

Remove the spark plugs one at a time, placing each in a tray marked with the corresponding cylinder numbers.

Tighten them to 15 N.m (11 lb ft) for 4.3L, 5.0L, and 5.7L engines with iron heads, 20 N.m (15 lb ft) for 7.4L engines with iron heads, and 30 N.m (22 lb ft) for new iron heads across all engine sizes.

Remove the spark plugs one at a time, placing each in a tray marked with the corresponding cylinder numbers.

For new iron heads, tighten to 30 N.m (22 lb ft).