Jeep WJ Grand Cherokee Spark Plugs

By Jeep Experts

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General data

Both the 4.0L 6–cylinder and the 4.7L V-8 engine use resistor kind spark plugs. 4.7L V-8 engines are geared up with “fired in suppressor seal” kind spark plugs utilizing a copper core floor electrode. Because of the usage of an aluminum cylinder head on the 4.7L engine, spark plug torque may be very vital. To stop potential pre-ignition and/or mechanical engine injury, the right kind/warmth vary/quantity spark plug have to be used.

The 4.7L V–8 engine makes use of 8 devoted, and individually fired coil for every spark plug. Each coil is mounted on to the highest of every spark plug. Battery voltage is equipped to the 8 ignition coils from the ASD relay. The Powertrain Control Module advance. This is completed to fulfill altering engine working situations. The ignition coil isn’t oil crammed. The windings are embedded in an epoxy compound. This supplies warmth and vibration resistance that permits the ignition coil to be mounted on the engine. Because of coil design, spark plug cables (secondary cables) should not used.

Some gasoline refiners in a number of areas of the United States have launched a manganese additive (MMT) for unleaded gasoline. During combustion, gasoline with MMT causes the whole tip of the spark plug to be coated with a rust coloured deposit. This rust coloration could be misdiagnosed as being attributable to coolant within the combustion chamber. Spark plug efficiency could also be affected by MMT deposits.

COLD FOULING/CARBON FOULING

Cold fouling is usually known as carbon fouling. The deposits that trigger chilly fouling are principally carbon. A dry, black deposit on one or two plugs in a set could also be attributable to sticking valves or faulty spark plug cables. Cold (carbon) fouling of the whole set of spark plugs could also be attributable to a clogged air cleaner factor or repeated quick working instances (quick journeys).

WET FOULING OR GAS FOULING

A spark plug coated with extreme moist gasoline or oil is moist fouled. In older engines, worn piston rings, leaking valve information seals or extreme cylinder put on could cause moist fouling. In new or lately overhauled engines, moist fouling could happen earlier than break-in (regular oil management) is achieved. This situation can normally be resolved by cleansing and reinstalling the fouled plugs.

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OIL OR ASH ENCRUSTED

If a number of spark plugs are oil or oil ash encrusted, consider engine situation for the reason for oil entry into that exact combustion chamber.

SCAVENGER DEPOSITS

a standard situation attributable to chemical components in sure fuels. These components are designed to vary the chemical nature of deposits and reduce spark plug misfire tendencies. Notice that accumulation on the bottom electrode and shell space could also be heavy, however the deposits are simply eliminated. Spark plugs with scavenger deposits could be thought-about regular in situation and could be cleaned utilizing normal procedures.

CHIPPED ELECTRODE INSULATOR

A chipped electrode insulator normally outcomes from bending the middle electrode whereas adjusting the spark plug electrode hole. Under sure situations, extreme detonation may also separate the insulator from the middle electrode. Spark plugs with this situation have to be changed.

PRE-IGNITION DAMAGE

Pre-ignition injury is normally attributable to extreme combustion chamber temperature. The middle electrode dissolves first and the bottom electrode dissolves considerably latter. Insulators seem comparatively deposit free. Determine if the spark plug has the right warmth vary ranking for the engine. Determine if ignition timing is over superior or if different working situations are inflicting engine overheating. (The warmth vary ranking refers back to the working temperature of a specific kind spark plug. Spark plugs are designed to function inside particular temperature ranges. This relies upon upon the thickness and size of the middle electrodes porcelain insulator.)

SPARK PLUG OVERHEATING

Overheating is indicated by a white or grey middle electrode insulator that additionally seems blistered. The improve in electrode hole will probably be significantly in extra of 0.001 inch per 2000 miles of operation. This suggests {that a} plug with a cooler warmth vary ranking must be used. Over superior ignition timing, detonation and cooling system malfunctions may also trigger spark plug overheating.

CLEANING AND GAPPING (Except HO engines)

The plugs could also be cleaned utilizing commercially out there spark plug cleansing tools. After cleansing, file middle electrode flat with a small level file or jewelers file earlier than adjusting hole. The Gap specification is 0.035 for the 4.0L engine, and 0.040 for the 4.7L engine.

CAUTION: Never use a motorized wire wheel brush to wash spark plugs. Metallic deposits will stay on spark plug insulator and can trigger plug misfire.

CLEANING AND GAPPING (HO engines)

Never clear spark plugs on the 4.7L H.O. engine. Damage to the platinum rivet will consequence. Also, don’t use a wire-type gapping instrument for a similar purpose. Use a tapered-type gauge. The Gap specification is 0.040 for the 4.7L HO engine.

PLUG REMOVAL & INSTALLATION – 4.0L

4.0L Plug: Mopar® P/N SP000ZFR5N    Gap: 0.035    Torque: 26-30 ft. lbs.On the 4.0L 6–cylinder engine, the spark plugs are positioned beneath the coil rail meeting.

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A one-piece coil rail meeting containing three particular person coils is used on the 4.0L engine. The backside of the coil is supplied with 6 particular person rubber boots to seal the 6 spark plugs to the coil. Inside every rubber boot is a spring. The spring is used for {an electrical} contact between the coil and the highest of the spark plug. Originally, the rubber boots and is derived weren’t bought individually, the whole coil rail with boots needed to be bought as one meeting. The boots/springs are actually out there individually from Mopar and from auto elements shops.

Removal

Tips: 6″ socket extension; use anti-sieze within the rubber socket for simple launch off the plugs

1. Disconnect unfavorable battery cable at battery.

2. The coil rail meeting have to be eliminated to achieve entry to any/all spark plugs. The coil is bolted on to the cylinder head. Remove the 4 coil mounting bolts.

3. Carefully pry up coil meeting from spark plugs. Do this by prying alternately at every finish of coil till rubber boots have disengaged from all spark plugs. If boots is not going to launch from spark plugs, use a commercially out there spark plug boot elimination instrument. Twist and loosen a couple of boots from a couple of spark plugs to assist take away coil.

4. After coil has cleared spark plugs, place coil for entry to main electrical connector. Disconnect connector from coil by pushing slide tab outwards to proper facet of car. After slide tab has been positioned outwards, push in on secondary launch lock on facet of connector and pull connector from coil.

5. Remove coil from automobile.

6. Prior to eradicating spark plugs, spray compressed air round spark plug gap and space round spark plug. This will assist stop overseas materials from coming into combustion chamber.

4. Remove spark plug from cylinder head utilizing a 5/8″ spark plug socket with a rubber insert. The rubber insert kind socket is required to take away the spark plug from the nicely after it’s unthreaded.

5. Note spark plug situation. You could need to mark the cylinder # on every used plug as they’re eliminated.

6. If boots are worn or broken they need to get replaced. To take away the rubber boots pull firmly and they’ll come proper off. To take away the spring, pull and stretch it just a little bit, after which twist counterclockwise to take away.

Installation

Special care must be taken when putting in spark plugs into cylinder head spark plug wells. Be certain plugs don’t drop into plug wells as floor straps could also be bent leading to a change in plug hole, or electrodes could be broken.

Always tighten spark plugs to specified torque. Over tightening could cause distortion leading to a change in spark plug hole or a cracked porcelain insulator.

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1. Verify that every plug is accurately gapped to 0.035. Apply a small quantity of anti-sieze to the plug threads. Start spark plug into cylinder head by hand to keep away from cross threading. It’s finest to do that by utilizing simply the socket extension bar and socket. Carefully flip slowly whereas protecting the extension bar as vertical as potential. You ought to be capable of screw the plug all the best way in by hand till it “seats” snugly.

2. Tighten spark plugs to 26-30 ft. lbs. (35-41 N·m) torque. If you do not need a torque wrench set up plugs cosy after which flip 1/4 flip.

3. Connect engine harness connector to coil by snapping into place. Move slide tab in the direction of engine for a optimistic lock.

4. Position ignition coil rubber boots to all spark plugs. Push down on coil meeting till bolt bases have contacted cylinder head.

5. Install 4 coil mounting bolts. Loosely tighten 4 bolts simply sufficient to permit bolt bases to contact cylinder head. Do a ultimate tightening of every bolt in steps all the way down to 250 in. lbs. (29 N·m) torque. Do not apply full torque to any bolt first.

6. Connect unfavorable battery cable to battery.

7. To change worn boots/springs, set up the brand new spring by merely pushing the spring onto its put up (no twisting wanted). Push the brand new boots on over the brand new spring.

PLUG REMOVAL & INSTALLATION
4.7L V-8 / 4.7L V-8 HO

Note: 4.7L V-8 = engine VIN code “N”; 4.7L V-8 HO engine = VIN code “J”

4.7 Plug: Mopar® P/N SPRC12MCC4    Gap: 0.040

 

CAUTION: The normal 4.7L engine makes use of copper core floor electrode spark plugs, they have to be changed with the identical kind/quantity spark plug as the unique. If one other spark plug is substituted, pre-ignition will consequence.

 

4.7 HO Plug: Mopar® P/N SPRC7PYCB4*    Gap: 0.040

 

CAUTION: Never substitute the unique platinum tipped HO spark plug with a distinct half quantity. Serious engine injury could consequence.. HO plugs can’t be cleaned, injury to the platinum rivet will consequence. Also, don’t use a wire-type gapping instrument for a similar purpose. Use a tapered-type gauge. To stop potential pre-ignition and/or mechanical engine injury, the right kind/warmth vary/quantity spark plug have to be used.*NOTE on 4.7 HO plugs: Champion RC7PYCB4 (p/n 3340) is similar as Mopar SPRC7PYCB4 and could be bought for a fraction of the price that Mopar expenses.

 

Spark plug elimination

Each particular person ignition coil have to be eliminated to achieve entry to every spark plug. The coil matches into machined holes within the cylinder head. A mounting stud/nut secures every coil to the highest of the consumption manifold. The backside of the coil is supplied with a rubber boot to seal the spark plug to the coil. An o-ring is used to seal the coil on the opening into the cylinder head. Inside every rubber boot is a spring. The spring is used for a mechanical contact between the coil and the highest of the spark plug. Originally, the rubber boots and is derived weren’t bought individually, the whole coil rail with boots needed to be bought as one meeting. The boots/springs are actually out there individually from Mopar and from auto elements shops.

Spark plug removal & installation tools                                        4.7L ignition coil

1. Remove the throttle body resonator box and air duct:

 

Resonator box removal Resonator breather tube

 

A. Remove the two 10mm bolts, located in front on each side of the resonator.
B. With a flat-head screwdriver, loosen the tube clamp attaching the rubber hose to the throttle body at the back of the resonator.
C. Remove the small hose attached on the driver side rear of the resonator box.
D. Lift up and release the 4 spring clips that secure the air filter lid. You can now remove the resonator, hose and filter box top together as one assembly.

2. Start with the first plug on either side of the front of the engine. Disconnect the electrical connector from the coil by pushing downward on the release lock on top of the connector, then pull connector away from the coil (see photo below). It is best to perform the removal and installation process for each plug as you go along. Once an old plug is removed, reinstall the new plug as soon as possible to reduce the risk of anything falling into the exposed spark plug hole.

Coil capacitor mounting WJ 4.7 Ignition coil location

3. Remove the coil mounting nut from the mounting stud using a 10mm socket or wrench (see photo above left). Note that the rear plugs each have a ground strap that must be reinstalled back in the same location on the mounting stud. In addition, a coil capacitor is mounted on each side of the engine, attached to a coil mounting stud.

4. Carefully pull up coil from the cylinder head opening, a slight twisting action will help to free the seal.

5. Remove coil from vehicle.

Before removing each spark plug it’s a good idea to spray compressed air in and around the spark plug well. As plugs are removed and installed, extreme caution must be taken to avoid any debri falling into the exposed spark plug hole.

6. Remove spark plug from cylinder head using a 5/8″ deep socket with a rubber insert. It is important to have a socket with a grip insert so that the plug can be lifted out of the hole once it is completely loosened, and to assist in reinstalling the new plugs.

A note on the passenger side rearmost plug – this is the most difficult of the plugs to remove and install. You may have to push and hold the transmission dipstick firmly upward to obtain enough room to remove the coil. To remove the plug, feed a 6″ ratchet extension with spark plug socket down into the plug hole and push onto the spark plug. Then add a 2″ or 3″ extension onto the 6″ extension, add the swivel adaptor, add a 6″ extension to that, and finally the ratchet. This will allow enough room to turn the ratchet and loosen the plug. Once loose, remove the ratchet and all but the last extension and finish loosening the plug, turning the socket/single extension by hand. A small flashlight may be helpful when guiding the socket extensions in place. See the “tools” photo above for an idea of how ratchet pieces are hooked together.

Installation

Special care should be taken when installing spark plugs into cylinder head spark plug wells. Be sure plugs do not drop into plug wells as ground straps may be bent resulting in a change in plug gap, or electrodes can be damaged. Always tighten spark plugs to specified torque. Over tightening can cause distortion resulting in a change in spark plug gap or a cracked porcelain insulator.

1. Verify that each plug is correctly gapped to 0.040. Apply a small amount of anti-sieze to the plug threads. Start spark plug into cylinder head by hand to avoid cross threading. It’s best to do this by using just a socket extension bar and socket. Carefully turn slowly while keeping the extension bar as vertical as possible. You should be able to screw the plug all the way in by hand until it “seats” snugly.

2. Tighten spark plugs to 20 ft. lbs. (27 N·m) torque. If you do not have a torque wrench install plugs snug and then turn 1/4 turn.

3. Before re-installing each coil, check condition of coil o-ring and replace if necessary. Clean the outside of the coil tube with a damp rag. To aid in coil installation, apply a bead of dielectric grease to the coil o-ring and smooth it around the o-ring with your finger.

4. Position the ignition coil into the cylinder head opening and push it onto the spark plug. Do this while guiding the coil base over the mounting stud. For the rearmost coils on each side, be sure to reattach the ground straps before putting the nut on the stud. In addition, there is one coil capacitor on all sides that’s secured to the closest coil mounting stud.

5. Install the mounting stud nut with a 10mm socket or wrench and tighten to 70 in. lbs. (8 N·m) torque.

6. Connect electrical connector to coil by snapping into place.

7. When all 8 of the brand new plugs are put in, double-check that each one 8 electrical connectors are firmly seated and that each one 8 coil nuts are connected and tightened. Reattach the oil dipstick tube and verify that no different wiring or connectors have been disturbed or moved misplaced.

8. Install the resonator meeting. Start by aligning the quick rear tube to the throttle physique opening. It will take a agency push and a few slight twisting motion to seat it in place. You can then push down the entrance of the field, wiggling it some extra to align with the bolt tabs on prime of the manifold. Install each backside bolts with a 10mm socket or wrench. Reconnect the breather tube on the driving force’s facet, positioned in again of the resonator. Attach the air filter lid by securing the 4 spring clips.

9. Confirm that no instruments or elements have been left within the engine bay space. Start engine and verify for easy idle operation.

 

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