Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Routine Maintenance & Tune-Up

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Accessory Drive Belts



Accessory Belt Routing


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Fig. Accessory serpentine belt routing-4.2L engines



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Fig. Accessory serpentine belt routing-4.3L engines



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Fig. Accessory drive belt and A/C belt routing-5.3L engines

Adjusting

Serpentine belts are automatically tensioned by a system of idler and tensioner pulleys, thus require no adjustment. The serpentine belt tension can be checked by simply observing the belt acceptable belt wear range indicator located on the tensioner spindle. If the belt does not meet the specified range, it must be replaced.


NOTE
A belt is considered -used'' after 15 minutes of operation.



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Fig. Check the belt tension by simply observing the range indicator located on the tensioner spindle

Inspection

Inspect the drive belt for signs of glazing or cracking. A glazed belt will be perfectly smooth from slippage, while a good belt will have a slight texture of fabric visible. Cracks will usually start at the inner edge of the belt and run outward. All worn or damaged drive belts should be replaced immediately.

Removal & Installation
4.2L Engine
  1. Install 3 / 8  inch breaker bar on the drive belt tensioner arm and turn the breaker bar clockwise enough to relieve the tension on the drive belt.
  2.  
  3. Remove the drive belt.
  4.  
  5. Release the tension on the tensioner arm.

    Click image to see an enlarged view

    Fig. Accessory serpentine belt routing-4.2L engines

  6.  

To install:

  1. Route the drive belt over all the pulleys except the drive belt tensioner pulley.
  2.  
  3. Install the 3 / 8  inch breaker bar on the drive belt tensioner arm and turn the breaker bar clockwise.
  4.  
  5. Install the drive belt over the drive belt tensioner pulley.
  6.  
  7. Slowly release the tension to the drive belt tensioner arm.
  8.  
  9. Inspect for proper installation of the drive belt on the pulleys.
  10.  

4.3L Engines
  1. Using a 3 / 8 in. breaker bar, rotate the tensioner counterclockwise to relieve the belt tension.
  2.  
  3. Remove the serpentine belt.
  4.  

To install:

  1. Route the belt over all the pulleys except the tensioner.
  2.  
  3. Place the breaker bar and if necessary the socket, on the tensioner pulley bolt and rotate the tensioner counterclockwise to the released position.
  4.  
  5. Install the belt and return the pulley slowly to its original position. Do not let the pulley snap back into position as this may damage the belt and pulley.
  6.  
  7. Check that the belt is properly seated in each pulley.
  8.  

5.3L Engine
A/C Compressor Belt
  1. Remove the accessory drive belt.
  2.  
  3. Raise the vehicle.
  4.  
  5. Install a ratchet into the square opening of the air conditioning (A/C) belt tensioner.
  6.  
  7. Rotate the A/C belt tensioner clockwise in order to relieve tension on the belt.
  8.  
  9. Remove the A/C belt from the pulleys.
  10.  
  11. Slowly release the tension on the A/C belt tensioner.
  12.  
  13. Remove the ratchet from the A/C belt tensioner.
  14.  
  15. Clean and inspect the belt surfaces of all the pulleys.

    Click image to see an enlarged view

    Fig. Accessory drive belt and A/C belt routing-5.3L engines

  16.  

To install:

  1. Install the A/C belt around the crankshaft balancer.
  2.  
  3. Install a ratchet into the square opening of the A/C drive belt tensioner.
  4.  
  5. Rotate the A/C belt tensioner clockwise in order to relieve tension on the belt.
  6.  
  7. Install the A/C belt over the idler pulley.
  8.  
  9. Install the A/C belt around the A/C compressor pulley.
  10.  
  11. Slowly release the tension on the A/C belt tensioner.
  12.  
  13. Remove the ratchet from the A/C belt tensioner.
  14.  
  15. Inspect the A/C belt for proper installation and alignment.
  16.  
  17. Lower the vehicle.
  18.  
  19. Install the accessory drive belt.
  20.  

Accessory Drive Belt
  1. Remove the air cleaner outlet duct.
  2.  
  3. Install a breaker bar with hex-head socket to the drive belt tensioner bolt.
  4.  
  5. Rotate the drive belt tensioner clockwise in order to relieve tension on the belt.
  6.  
  7. Remove the belt from the generator pulley.
  8.  
  9. Slowly release the tension on the drive belt tensioner.
  10.  
  11. Remove the breaker bar and socket and from the drive belt tensioner bolt.
  12.  
  13. Remove the belt from the remaining pulleys.
  14.  
  15. Clean and inspect the belt surfaces of all the pulleys.

    Click image to see an enlarged view

    Fig. Accessory drive belt and A/C belt routing-5.3L engines

  16.  

To install:

  1. Route the drive belt around all the pulleys except the generator pulley.
  2.  
  3. Install the breaker bar with hex-head socket to the belt tensioner bolt.
  4.  
  5. Rotate the belt tensioner clockwise in order to relieve the tension on the belt.
  6.  
  7. Install the drive belt on the generator pulley.
  8.  
  9. Slowly release the tension on the belt tensioner.
  10.  
  11. Remove the breaker bar and socket from the belt tensioner bolt.
  12.  
  13. Inspect the drive belt for proper installation and alignment.
  14.  
  15. Install the air cleaner outlet duct.
  16.  

Firing Orders





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Fig. 4.3L Engines Firing order: 1-6-5-4-3-2

Fuel Filter



Removal & Installation
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  
  5. Remove or disconnect the following:

    Negative battery cable and fuel filler cap, if not already done
     

  6.  
  7. Raise and support the vehicle.

    Fuel tank shield, if equipped
     
    Quick connect fittings from the filter
     
    Filter feed nut and the clamp bolt
     
    Filter and the clamp from the vehicle

    Click image to see an enlarged view

    Fig. Typical fuel filter location along frame rail

     

  8.  

To install:

  1. Install or connect the following:
    NOTE
    The filter has an arrow (fuel flow direction) on the side of the case, be sure to install it correctly in the system, the with arrow facing away from the fuel tank.



    Filter and clamp with the directional arrow facing away from the fuel tank, toward the throttle body
     



    Tighten the fuel feed nut
     
    Tighten the filter clamp assembly bolt
     
    Fuel quick disconnect fittings to the filter
     
    Fuel tank shield, if equipped
     
    Fuel filler cap
     
    Negative battery cable
     

  2.  
  3. Start the engine and check for leaks.
  4.  

Idle Speed & Mixture Adjustments



Idle speed is maintained by the Powertrain Control Module (PCM). No adjustment is necessary or possible.

Ignition Timing



Checking & Adjusting

The ignition timing is preset and cannot be adjusted.

Spark Plugs & Wires



Spark Plugs
Inspection and Gapping

Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%.

Check spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag.


NOTE
NEVER adjust the gap on a used platinum type spark plug.

Always check the gap on new plugs as they are not always set correctly at the factory. Do not use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A round-wire type gapping tool is the best way to check the gap. The correct gauge should pass through the electrode gap with a slight drag. If you're in doubt, try one size smaller and one larger. The smaller gauge should go through easily, while the larger one shouldn't go through at all. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely never attempt to bend the center electrode. Also, be careful not to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.

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Fig. Inspect the spark plug to determine engine running conditions



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Fig. A variety of tools and gauges are needed for spark plug service



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Fig. Checking the spark plug gap with a feeler gauge



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Fig. Adjusting the spark plug gap



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Fig. If the standard plug is in good condition, the electrode may be filed flat-WARNING: do not file platinum plugs



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Fig. The spark plug gap specification is sometimes given on a underhood label located on the upper radiator shroud

Removal & Installation

A set of spark plugs usually requires replacement after about 20,000-30,000 miles (32,000-48,000 km), depending on your style of driving. In normal operation plug gap increases about 0.001 in (0.025 mm) for every 2500 miles (4000 km). As the gap increases, the plug's voltage requirement also increases. It requires a greater voltage to jump the wider gap and about two to three times as much voltage to fire the plug at high speeds than at idle. The improved air/fuel ratio control of modern fuel injection combined with the higher voltage output of modern ignition systems will often allow an engine to run significantly longer on a set of standard spark plugs, but keep in mind that efficiency will drop as the gap widens (along with fuel economy and power).

When you're removing spark plugs, work on one at a time. Don't start by removing the plug wires all at once, because, unless you number them, they may become mixed up. Take a minute before you begin and number the wires with tape.

  1. Disconnect the negative battery cable, and if the vehicle has been run recently, allow the engine to thoroughly cool.
  2.  
  3. Carefully twist the spark plug wire boot to loosen it, then pull upward and remove the boot from the plug. Be sure to pull on the boot and not on the wire, otherwise the connector located inside the boot may become separated.
  4.  
  5. Using compressed air, blow any water or debris from the spark plug well to assure that no harmful contaminants are allowed to enter the combustion chamber when the spark plug is removed. If compressed air is not available, use a rag or a brush to clean the area.
    NOTE
    Remove the spark plugs when the engine is cold, if possible, to prevent damage to the threads. If removal of the plugs is difficult, apply a few drops of penetrating oil or silicone spray to the area around the base of the plug, and allow it a few minutes to work.

  6.  
  7. Using a spark plug socket that is equipped with a rubber insert to properly hold the plug, turn the spark plug counterclockwise to loosen and remove the spark plug from the bore.
    WARNING
    Be sure not to use a flexible extension on the socket. Use of a flexible extension may allow a shear force to be applied to the plug. A shear force could break the plug off in the cylinder head, leading to costly and frustrating repairs.



    Click image to see an enlarged view

    Fig. Remove the spark plug wire by pulling on the boot



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    Fig. Using a spark plug socket with a rubber insert, turn the plug counterclockwise to loosen it



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    Fig. Remove the spark plug from the bore

  8.  

To install:

  1. Inspect the spark plug boot for tears or damage. If a damaged boot is found, the spark plug wire must be replaced.
  2.  
  3. Using a wire feeler gauge, check and adjust the spark plug gap. When using a gauge, the proper size should pass between the electrodes with a slight drag. The next larger size should not be able to pass while the next smaller size should pass freely.
  4.  
  5. Carefully thread the plug into the bore by hand. If resistance is felt before the plug is almost completely threaded, back the plug out and begin threading again. In small, hard to reach areas, an old spark plug wire and boot could be used as a threading tool. The boot will hold the plug while you twist the end of the wire and the wire is supple enough to twist before it would allow the plug to crossthread.
    WARNING
    Do not use the spark plug socket to thread the plugs. Always carefully thread the plug by hand or using an old plug wire to prevent the possibility of crossthreading and damaging the cylinder head bore.

  6.  
  7. Carefully tighten the spark plug. If the plug you are installing is equipped with a crush washer, seat the plug, then tighten about 1 / 4 turn to crush the washer. If you are installing a tapered seat plug, tighten the plug to specifications provided by the vehicle or plug manufacturer.
  8.  
  9. Apply a small amount of silicone dielectric compound to the end of the spark plug lead or inside the spark plug boot to prevent sticking, then install the boot to the spark plug and push until it clicks into place. The click may be felt or heard, then gently pull back on the boot to assure proper contact.
  10.  

 
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