This guide supplies a collection of information relating to troubleshooting the 1987 Dodge Ram 318 engine. The purpose is to provide a clear and accessible guide to those familiar with electrical and mechanical knowledge, but perhaps unfamiliar specifically with the Dodge Ram 318 engine.
This is intended as a guide to engine diagnostic procedures. It covers the main individual systems of the engine and provides an explanation of the function and individual problems of each part. Instructions for performing tests or examinations specific to the 318 engine are elaborated underneath respective parts.
Troubleshooting the spark delivery system: The components of the spark system are carefully calibrated to deliver the correct temperature spark at the right time. A malfunction in a system part may not be very noticeable at first. Some problems, such as a cylinder misfiring, can be caused by multiple systems. Do not automatically assume that one system is to blame.
The spark system consists of five main sections: the plugs and wires, distributor, resistor, coil, and spark timing.
Spark plugs and wires: The spark plug gap determines how far the spark must arc. To measure the gap, use the correct combination of feeler gauges or a similar tool. The spark plug gap should be set at exactly .035 inch (Chrysler, 122). Spark plug wires will eventually wear out from the high voltage that creates the spark. Bad wires will cause the engine to misfire because they cannot provide a hot enough spark to ignite the fuel mixture. The wires may be tested for continuity, but this will only reveal if they are capable of carrying low voltage. Suspect wires should be inspected visually. Cracked insulation, corroded connectors, corroded wire, and loose connections will all contribute to wire failure.
Distributor, cap and rotor: If the distributor cap or rotor is going bad, the engine may misfire or fail to run. The plastic cap can become deformed or cracked, or the points inside may become corroded or pitted from wear. Removing the cap and inspecting it visually may diagnose all of these problems. The rotor can become corroded or pitted from the constant voltage running from the tip to the points inside the cap. Spring tension may also become too weak to maintain pressure with the cap center point.
Ballast resistor: The ballast resistor limits voltage to the distributor at low speeds. If the ballast resistor fails, the engine will start and immediately shut off because the resistor is bypassed in the starting circuit to provide maximum voltage to the spark plugs. The resistor is checked with an ohmmeter for the correct resistance reading. The resistor should read between 1.1 and 1.8 ohms (Hayden, 5-2).
Ignition coil: The ignition coil delivers extremely high voltage to the spark plugs. Without the coil in the circuit, the voltage is not high enough to arc the spark plug gap and create a spark. To check the primary coil, measure the resistance between the two small connectors. To measure the resistance of the secondary, connect an ohmmeter between the large center connector and ground. Make sure the coil is disconnected when this is done, or incorrect readings may result. The primary ignition coil should read between 1.34 and 1.55 ohms. The secondary coil should read between 9.0 and 12.2 ohms (Hayden, 5-1).
Mechanical spark timing: The correct spark timing on 1987 engines is 8 degrees advanced of top dead center (Chrysler, 90).
Measuring spark timing: This procedure uses an electronic timing light to align the number one spark with the number one piston on the firing stroke. Step 1: With the ignition off, connect the power leads of a timing light to the battery terminals, and the diagnostic lead to the number one spark plug wire. Step 2: Disconnect all wires or vacuum hoses from the distributor. This will ensure that the timing is not affected. Step 3: Start the vehicle and activate the timing light. Step 4: Aim the light toward the timing bracket. The bracket is located below the water pump on the driver’s side of the timing chain cover. There is a mark on the harmonic balancer that will correspond with one on the bracket. Read the number off of the bracket that appears next to the balancer mark when the timing light flashes. Conclusion: If the marks align at the upper number eight, then the timing is adjusted correctly. If the number is either lower or higher, the timing must be adjusted. Note: There are two sets of numbers: one with marks from ten to zero on the upper side, and one with marks from zero to ten. The upper numbers are the advanced timing marks; the lower numbers signify retarded timing. The zero between the sets is top dead center for the number one piston.
How spark plugs wear: Spark plugs are responsible for igniting the mixture of compressed air and gasoline in the cylinders with an arc of high voltage DC electricity. The plug is constructed of an electrode surrounded by a ceramic insulating core. Electricity arcs from the electrode to the grounded rim of metal surrounding the ceramic core.
There are three main types of spark plug wear. Normal wear occurs during usual operation. Second, damage from a malfunction causes unusual wear. Last, improper adjustment can cause damage as well.
Wear under normal use: The electrode and ceramic will become discolored with age, usually turning a dark brown color. Small carbon deposits ordinarily appear as dry black deposits that flake off easily. Slight electrode pitting could occur from the high voltage.
Malfunctions: There are several main malfunctions that occur to spark plugs when neighboring components fail.
Oil leaks: Oil in the combustion chamber will leave large deposits of oily black carbon on the end of the spark plug. Some oil may also be forced up into the threads of the plug. “Fouled” plugs will cause the engine to lose power because the arc is diminished.
Electrode pitting: A deeply pitted and deteriorated electrode indicates that the combustion chamber has been running too hot. Weakening of the metal from the extreme heat causes the pitting which may also be accompanied by a deep discoloration of the metal and ceramic. A fuel mixture that is adjusted too lean may cause the cylinder to run hot.
Mechanical damage: The top of the piston can crush the electrode if the connecting rod breaks or an improper connecting rod has been installed.
Improper adjustment: The spark plug gap is very important in determining the heat of the arc (Chrysler, 86). Adjusting the gap changes the distance between the electrode and the ground side of the circuit. An incorrectly adjusted gap may allow overheating of the metal, or loss of power from a weak spark.
Conclusion: Examination of spark plugs can prevent larger problems from developing by catching small ones early. Understanding how spark plugs develop problems aids the diagnostic process.
Battery: The problems associated with a faulty battery or corroded battery cables may often be mistaken for some other problem. If the battery is completely dead, it will read a trace voltage level with a meter. If the battery is suspected, first check the electrolyte, or water level. Switching on the headlights of the vehicle, and observing the brightness can quickly diagnose the state of the battery. If the headlights are dim, then the battery has a low voltage charge. Failure of the battery will cause all electrical systems of the vehicle to fail with the engine shut off.
Battery electrolyte test: Electrolyte in a lead-acid battery determines how well the battery can hold a charge. The level will decrease with age as the distilled water evaporates from the mixture, even in a “no maintenance” battery. Step 1: With the ignition off, carefully pry off the two raised caps on top of the battery. Warning: Lead-acid battery electrolyte is a highly corrosive substance. Use extreme caution when performing this operation. Step 2: Observe the level of the electrolyte in each cell of the battery. The level should come up to the bottom rim of each cell. Conclusion: If the electrolyte level is fine in each cell, then the electrolyte level is not causing an electrical problem.
Alternator: The alternator on 1987 engines may be checked with a “full-fielding” test (Hayden 5-15). This process bypasses the voltage regulator and puts the full alternator output back into the field. Low belt tension will reduce alternator output. The alternator belt should deflect about a quarter inch between pulleys when adjusted correctly.
“Full-fielding” test for Chrysler alternators: “Full-fielding” indicates whether a Chrysler alternator is functioning properly. This test bypasses the voltage regulator, allowing the alternator’s full voltage to reach the rotor, or field, unaltered by any other component. Step 1: Make sure the ignition switch is in the off position. Remove the connector from the voltage regulator, located on the firewall. If the location is in doubt, trace the two small-gauge wires (dark blue and dark green) leading from the alternator directly to the voltage regulator connecter. Step 2: Connect a jumper wire between the dark green wire of the voltage regulator connector (removed in step one) and ground. Note: It is easier to connect from this location than from the alternator itself, though either connection may be used. Step 3: Connect one lead of a voltmeter, capable of reading up to 20 volts DC, to each battery terminal. Make sure that the meter may be read from the location the vehicle will be started from, or by an assistant. Step 4: Start the vehicle and operate the engine only long enough to take a meter reading. Warning: Do not operate the engine longer than necessary. Because the voltage regulator is disconnected, voltage higher than 16 volts could damage electronic components. Conclusion: If the meter reading is between 14 and 16 volts (normal operating voltage) the alternator is functioning properly. If it is significantly below 14 volts the unit is faulty.
Voltage regulator: The regulator filters the voltage supplied to the electrical system by the alternator. High voltage spikes or constant high voltage signify a problem. The voltage regulator is bad if the charging voltage is very high. A reading of over 16 volts indicates that the regulator is defective.
Ammeter: The 1987 ammeter has a shunt circuit (see electrical schematic). If the ammeter should fail, it will not cause any other systems to stop working. Disconnecting the meter from the circuit and connecting a handheld ammeter in its place will check the ammeter. If the reading on the handheld meter is correct, and the circuit meter is not, then the meter is faulty.
The starting system uses a lead-acid battery to power an electric starter motor meshed to a ring gear at the rear of the engine. A keyed interlock switch on the steering column operates a relay to supply power to the starter solenoid. This solenoid engages the starter motor, which rotates the engine to begin the internal combustion process.
The starting system includes the starter motor, ignition solenoid, starter solenoid, and all wiring between the modules. The charging system includes the alternator, voltage regulator, battery, ammeter, and all wiring connecting these units. The alternator is a belt-driven engine accessory that supplies power to the electrical system during engine operation. It also recharges the battery with surplus amperage. The output is kept at a constant level by the voltage regulator.
Starter motor test: Comparing the cranking speed against the voltage drain on the battery will diagnose the starter (Hayden, 5-22). Voltage drain from the battery during cranking has a direct relation to starter performance. Step 1: Connect one lead of a voltmeter, capable of reading up to 20 volts DC, to each battery terminal. Make sure that the meter may be read from the location the vehicle will be started from, or by an assistant. Step 2: Disconnect the large center wire from the ignition coil. Step 3: Rotate the engine a few times with the starter motor. Conclusion: If the engine cranks slowly, and the voltage of the battery is above 9 volts during starter operation, either the starter motor is faulty or the engine itself is partially seized. If the voltage is above 9 volts during cranking, the motor is good.
Ignition switch: The switch can be checked for function with a meter at the wiring harness at the bottom of the steering column. Refer to the wiring schematics for the correct wires. Note that the switch/starter circuit is protected by fusible links, and if these go bad the switch will function but current will not pass to the starter. These fusible links are above the driver's side fender.
Starter solenoid: The solenoid for the starter motor is mounted on the motor itself (see starter motor in electrical schematic). Since it engages the motor gear into the ring gear of the engine, it makes an audible click if it is working properly. If the solenoid is not audible, then the coil may be tested for continuity with a meter. If the coil has no continuity, then the solenoid is faulty (McWhorter, 24).
Notes: Although the starting and charging systems appear to be independent, they must both operate with the common link of the battery. Difficulties in either of the systems could cause the other to malfunction also. Extreme care should be taken to diagnose problems carefully.
Engine bearing wear: Inspecting engine bearings can reveal how the engine systems are operating. This process describes the ways that bearings wear in logical progression from the inside out. Small problems in the first stage usually lead to larger problems in the later stages. Traditionally, Babbitt was used to construct the entire bearing, but the extreme softness of the material led to early failure. Modern bearings have only a thin coating of the alloy inside a stronger metal. Bearings will develop patterns of wear in the thin Babbitt coating on the inner surface that can reveal how individual parts or systems are performing. There are individual defects that signify these problems. Secondly, the outside will reveal marks if a larger malfunction has occurred, since only the Babbitt surface is a point of normal wear. Finally, complete sets of bearings may be placed together in order to reveal even larger malfunctions involving multiple parts. All of the bearings in a set should be completely removed for systematic examination.
Alloy surfaces: The face of the bearing should be examined first to see how well normal wear has affected it. Attention to extreme detail is important when examining a soft alloy such as Babbitt. Every cause of slight pressure in the surface will leave a different mark. The color of the material is important as well. Since Babbitt is affected by heat, elevated temperatures will leave a graduated discoloration comparable to the heat level. On one end, there is a semi-circular cutout for oil flow. This should be carefully inspected because it greatly affects larger factors.
Low oil pressure: If low oil pressure has tampered with the bearing, the surface will be worn away from prolonged contact with the connecting rod. Strong indications of nonexistent or low oil pressure will appear at identical points located midway on both of the bearing halves. The marks are caused by the connecting rod impacting at the top and bottom of the piston stroke without oil protection.
Dirt contamination: Dirty oil or debris will scratch the surface and leave a rotational imprint. This can affect oil flow and cause early bearing failure. Dirt can come from poor pre-assembly cleaning or improperly filtered oil.
Antifreeze contamination: Antifreeze in the oil will eat away sections of the bearing surface with an acid-like process. Patches of alloy will be missing from the surface (see photo).
Overheating: Dangerously hot connecting rods will discolor the entire bearing, leaving some sections a dull reddish tint (see photo). The darker the tint, the hotter the temperature has risen. Overheated rods will cause the rod to weaken and eventually break or bend.
Improper oil flow: The oil circulation cutout should not show any signs of compression that indicates restriction. This leads to oil pressure loss and spun or nested bearings, or vice versa.
Outside surfaces: The back and outside of the bearing should be examined to see if there are secondary problems involving abnormal wear such as mismatched parts. The back has a machined pattern and stamped identification. The stamping includes date of manufacture and the size of the bearing stamped either standard (STD), or a number indicating the oversize. There is a notch on the rear of each bearing half used to center the bearing within the connecting rod. Any nicks or scraping of the outside surface should be immediately identified and are prompt indicators that something is wrong. The back of the bearing should not be worn at all, and any problems causing damage to this part of the bearing should be evident because there will be severe wear on neighboring parts as well.
Spun bearings: Spun bearings, or those that have broken free and spun separately from the connecting rod, will have the underside notch flattened, and will be worn on the back as well as the front (see photo). Spun bearings make a shrill screech very similar to a worn accessory belt. Binding between the bearing alloy surface and the metal face of the connecting rod causes this damage.
Nested bearings: Nested bearings, or those halves that have spun around to sit on top of each other, will flatten the bearing out like a sheet of paper (see photo). Nested bearings are caused by extremely worn, spun bearings, or oil pressure loss.
Examining bearing sets: By combining the techniques in the previous sections, bearings can be lined up in sets to examine similar patterns. If only one end of the engine has low oil pressure for example, this damage can be seen by those bearings on the bad end. This part of the process will pinpoint problems by location. Tracking down the cause of the problem will become faster and easier, as well as confirming early diagnosis by comparison.
Conclusion: The diagnosis process may be used with any set of bearings. Understanding what causes the problems is the key to preventing and fixing them.
For examples of what these look like, we have already reproduced for you six excellent examples. The photo shows bearings taken from the SAME 318 engine after various failures (for a testament to how durable these engines really are). For your enlightenment, we then rebuilt the engine and failed it again to produce the next example, and so on. Even after the connecting rod failure, the engine was still rebuilt and functioned perfectly, albeit requiring some new parts.
The upper end of the engine includes the valve train and cylinder heads. Problems in the valve train usually occur because of extreme wear, improper installation, or improper components. Symptoms of an upper end problem can include noises that occur at half crankshaft speed, or once every two engine revolutions. Most valve train problems will have some power loss associated with them. There are seven primary sections in the upper end of the engine: the camshaft and its bearings, lifters, pushrods, rocker arms, the intake and exhaust valves, the intake and exhaust ports, and finally the cylinder head itself.
Camshaft and bearings: Worn camshaft lobes are a common source of power loss because they will prevent the valves from opening completely. For measuring, the camshaft must be removed from the engine. Measurements should be carefully taken with a micrometer or caliper and compared against factory specifications. Extreme lobe wear may be identified in the engine by slowly rotating the camshaft and noting if the lifters rise out of their bores to a significant height. See photo for two specific examples of extreme wear. Camshaft bearings are one piece and press-fit. Bearings must be examined by removing the camshaft. If any bearing has failed or is beginning to fail, all of the bearings must be replaced. Extreme camshaft bearing failure is unlikely because of the lack of high forces that are associated with the other engine bearings. Bearings may still become cracked, pitted, scarred or deformed, and should be replaced. Several of the bearings have a hole for oil circulation. If these holes become obstructed, oil will not circulate properly to the valve train.
Lifters: Lifters used in 1987 engines are hydraulic. Normal wear usually occurs on the base of the lifter at the point where it contacts the cam lobe. The base will have a concave depression, or scarring if it is severely damaged. This may be confirmed by placing a straightedge across the bottom of the lifter.
Lifter pushrods: The pushrods are solid with rounded ends. Normal wear will either flatten or reshape the ends. Abnormal wear will bend or flex the rod and can be determined by rolling the rods over a piece of glass to see if they are warped. Bent rods are caused by over-tightening the rocker arms and placing too much pressure on the rod.
Rocker Arms: Rocker arms will wear at all points of contact with the parts around them. Exhaust rocker arms will wear against the side of intake rocker arms and vice versa. Wear will occur at contact points with the rods and valves. All rocker arm wear must be inspected visually.
Exhaust and intake valves: To properly diagnose a valve problem, the valves should be removed from the cylinder head. Some minor problems may be discernable externally, but small problems are easy to overlook. Valves will wear against their seats in the head itself. The face will become rounded under normal use, affecting flow of fuel and air. The bottom of the valve will become slightly corroded from the combustion process, and heavy corrosion on the valve face will cause leaking and extreme compression loss. Instructions for checking compression are included in the section describing piston ring problems. The valve stem will wear over time where it rides inside the head. This can be measured only with the valve removed. The top of the stem will also wear at the contact point with the rocker arm. Extreme wear here is unusual if proper lubrication is provided to the system.
Cylinder head surfaces and gaskets: Under constant operation, extreme forces are exerted on the cylinder heads. Over time these forces may slowly deform either the heads themselves or the gaskets between the engine block and the heads. Measurement is possible only with the heads removed and the lower side exposed. Laying a straightedge across the bottom will reveal minute changes if the head has warped. Examining the removed gasket will reveal how well it has performed. If there are leaks between the head and the engine block, these will be evident on the gasket face. A leaking head gasket will discharge coolant into the lubrication system and form a white, frothy substance from the mixture of oil, water, and antifreeze. This mixture reacts with soft alloys and will quickly disintegrate Babbitt bearing surfaces. Before removing the head to diagnose a leaking cylinder head gasket, first examine the dipstick. If there is no antifreeze evident in the oil, it is unlikely that the gasket is leaking badly.
Exhaust and intake ports: Corrosion from exhaust gases will build up on the inside of the exhaust ports, changing airflow and causing minor power loss. These deposits are visible with the exhaust manifolds removed. Intake port corrosion is rare because the gases entering through them are “clean” and un-burnt. If there is noticeable build-up, the air cleaner or fuel filter should be carefully examined for obstructions.
Failure of a lower end component will nearly always result in an audible sign, complete engine failure, or very extreme power loss. If a component fails, it is likely that one has affected another also. Prompt diagnosis of any of these problems is crucial because a warning sign means something has already begun to fail. The lower end of the engine consists of nine main stages. The crankshaft is the focal point of the lower end. The connecting rods, wrist pins, pistons, rings, flywheel, damper, valve timing and belts all derive their motion from the crankshaft.
Crankshaft and bearings: Crankshaft bearings will wear slower than connecting rod bearings under normal conditions. Crankshaft journals, including both connecting rod journals and main journals, will show signs of wear that can help diagnose other problems. Scuffing or scratches on the surface indicates too much dirt or debris in the lubrication system. Deformed journals show that the connecting rod caps were over tightened. Bearing failure will leave extreme deformation or discoloration. Journal measurements should be compared to factory specifications with a micrometer or caliper.
Connecting rods and bearing assemblies: Connecting rods and bearings must withstand extreme forces. As combustion pushes the piston downward, the force of the explosion is transmitted through the connecting rod into the crankshaft journal. Rods will sometimes bend slightly from the pressures and must be carefully examined to determine if they are a problem. The rod bearings must withstand both the down pressure from the rod and the rotational force of the rod around the crankshaft journal. Connecting rod bolts that are over tightened will cause bearing failure because the cap will be deformed. This will also deform or damage the crankshaft rod journal.
Connecting rod bearings: Connecting rod bearings prevent excessive friction between the crankshaft and connecting rod. The circular bearing is approximately 2 inches in diameter, 5/8 inch wide, and 3/32 inch thick with a hollow center to form a ring around the crankshaft journal underneath the end of the connecting rod. It is constructed in two pieces that mate into the upper and lower section of the connecting rod respectively. Upper bearing half: The upper section of the bearing is exactly half a ring. The bearing is constructed of steel outside, Babbitt inside, with a copper-lead alloy sandwiched in between. The soft white metal Babbitt alloy surface on the inside allows the iron crankshaft journal that spins against it to develop less wear. The 5/8 inch wide end where the bearing halves meet contains a half-circle cutout with a 1/16 inch radius. The outside of the opposite end has a right triangle shaped tab with the right angle against the steel and the end where the two bearing halves would meet. This triangle is cast into the steel, about 1/8 inch wide by 1/16 inch high, and is slightly offset from the center to one side. Lower bearing half: The lower bearing half is constructed exactly like the upper half, but as a mirror image so that the so that the identical ends mate to each other. When the two halves are placed together, they form a complete ring around the crankshaft journal and mate with the connecting rod. There is a circular hole where the halves meet to allow oil to flow inside the bearing between the crankshaft journal and the Babbitt surface. Each half aligns with its connecting rod surface via a triangular protrusion on the outside. For more details see here.
Wrist pins: Correctly installed wrist pins should not fail unless the connecting rod or piston fails. If the pin is too tight, it will add extra resistance to the engine and reduce horsepower. If it is too loose, it could cause the piston to fail.
Piston heads: Piston failure is rarely an isolated event, but generally secondary to other component malfunctions such as a crankshaft or connecting rod problem. Corrosion from the combustion process will form on top of the piston. This is the only expected wear.
Connecting rods: If the rod has broken on the down stroke, there is a possibility that the piston has fallen down the cylinder and impacted with the crankshaft weights. This will break the bottom of the piston skirt. If the connecting rod failed on the upstroke, the valves may have damaged the top of the piston, or vice-versa. Dirt or debris trapped between the side, or face, of the piston and the cylinder wall will vertically scuff the piston face (Adkins, 84).
Rings and oil scraper rings with spacer: If the engine is burning large quantities of oil, the piston rings may be worn, allowing a large quantity of burnt oil to be emitted with the exhaust gases. Performing a compression test to measure how tightly the rings seal against the cylinder walls will determine their condition.
Measuring compression: There should be 100 pounds per square inch (PSI) minimum with 25 PSI maximum variation between cylinders (Hayden, 2C-2). Piston rings and valves will wear over time, reducing the seal of the combustion chamber. The test uses a pressure gauge to determine the PSI compressed by the piston during several strokes. Step 1: With the ignition off, remove all of the spark plugs from the engine, and thread the end of the pressure gauge into the spark plug hole of the cylinder being tested. Step 2: Make sure the gauge is calibrated with the zero setting by depressing the release valve until the needle has fallen to zero. Step 3: Turn the engine over several revolutions to build up a pressure reading on the gauge. If no reading is indicated, check the tightness of the end of the gauge threaded into the spark plug hole. Conclusion: To find the general condition of all of the piston rings and valves, repeat this test for every cylinder to arrive at an average reading. If any specific cylinders vary greatly from the others, their components are worn more or the readings are incorrect.
Flywheel/ flex plate and ring gear: The ring gear is located on the torque converter in vehicles with automatic transmissions. Manual transmissions have no flex plate, and the flywheel/ ring gear is bolted directly to the crankshaft. The starter motor may still rotate the engine if one tooth is missing from the ring gear, but it will make a loud knock every time the starter pinion passes over that location. The starter cannot rotate the engine if more than one consecutive gear is broken or missing. A bent flywheel or flex plate can be found by spinning it in a fixed location to observe warping.
Harmonic balancer: Harmonic balancers, or vibration dampers, on 1987 engines have an inner steel core that bolts to the crankshaft with an outer steel core weight cushioned by a thin rubber seal designed to filter out unwanted vibration on the lower end of the engine. If the rubber seal between the cores starts to disintegrate, the outer part will separate and cause uneven engine balance. The primary indicator is extremely uneven vibration.
Mechanical valve timing: Aligning the valves with the proper point in the combustion cycle is achieved by a double link timing chain and gear set in a 2:1 ratio. Each valve opens only once in every two crankshaft revolutions. The timing chain may develop slack, and the keys for the timing gears may become broken. If severe and erratic timing errors evolve, check the keys. Even though a key is broken, the engine may still run because the gear has been allowed to rotate only slightly.
Measuring timing chain deflection: A loose or worn timing chain will cause power loss from incorrect valve timing. Step 1: With the timing chain cover removed and the ignition off, place a ruler or measuring device behind the timing chain at the midpoint between the upper and lower gears on the passenger side of the vehicle to measure deflection. Step 2: With a socket and breaker bar on the harmonic balancer bolt, rotate the engine a few degrees counter-clockwise until the pressure on the chain is relieved. Step 3: Pull the chain away from the gear set toward the passenger side of the vehicle. Note the measurement of distance that the chain is allowed to travel from the normal position. Conclusion: If the deflection is greater than a quarter inch the chain could cause some power loss.
Accessory belts: The rubber “V” belts that operate the alternator, power steering hydraulic pump, and the air pump may become worn or break. Signs of wear will appear as transverse lines and cracks in the rubber.
Troubleshooting carburetion systems: Carburetion on the 1987 318 engine is accomplished with a cast-aluminum two-barrel carburetor mounted on a heated cast-iron intake manifold. The system draws fuel from a mechanical pump powered by an eccentric on the end of the camshaft. Air is drawn past a single choke plate on the top of the carburetor. Both air and fuel atomize inside the barrels of the carburetor to create an air and fuel emulsion (Stubblefield, 3-7). The mixture is pulled down the intake manifold runners into the cylinders to be compressed by the piston and ignited by the spark plug. The carburetion system contains four main parts: the intake manifold, carburetor, fuel pump, and finally the pump eccentric.
Intake manifold: The cast-iron intake manifold conducts the fuel mixture to the valves through a series of runners. It is warmed by coolant from the engine and by heat conducted from the engine itself that allows the mixture to atomize better inside the passageways. Little wear should occur at the intake manifold. The gaskets may develop leaks over long mileage, but this is rare. Leaks due to improper installation are more common. There are coolant passages that run through the intake manifold, and leaks here will be evident at each corner. Coolant will collect in the depressions at the corner bolt heads.
Carburetor: Carburetion is an individual science that is well covered in dedicated troubleshooting manuals. For this reason, only the main mechanical difficulties that are linked to other engine operations are covered in this section. The carburetor contains two primary mechanical assemblies: the choke and the throttle.
Choke plate and linkage: The choke delivers a richer mixture to the engine in cold temperatures by closing a single choke plate. This action decreases the air available to the engine (Stubblefield, 3-5). A bimetal thermostat in the intake manifold controls the choke and cold idle (Stubblefield, 3-7). To test the thermostat, remove and place it in a bucket of hot water. The spring should visibly contract. If the engine runs well cold but misfires and eventually dies when hot, examine the choke.
Throttle plates and linkage: The two throttle plates are linked together, although situated in separate barrels of the carburetor. Opening these plates allows more of the mixture to reach the engine and increases the combustion, which increases the speed of the combustion process. This increases engine speed. The dual-plate throttle is cable operated. If the accelerator pedal is loose, then the cable is at fault. The cable should be properly adjusted so that the throttle is completely open when the accelerator is pressed to the floor.
Fuel pump and lines: An arm that rises and falls as the pump eccentric rotates operates the mechanical fuel pump. Fuel is drawn from a tank and pressurized into the system. There should be at least several PSI of fuel pressure in the secondary side of the system during engine operation. The fuel system uses an inline filter between the pump and the carburetor. If this filter becomes clogged, very little, or contaminated, fuel will reach the engine (Chrysler, 87). The metal fuel line should be free of extreme bends. Small kinks will cause the engine to misfire in higher power bands, yet run normally at idle.
Fuel pump eccentric: The eccentric is mounted on the forward end of the camshaft aligned with the camshaft keyway. It is engineered to deliver evenly spaced transmission of energy to the pump, so the eccentric is only slightly out-of-round. As the eccentric controlling the fuel pump arm wears, less fuel will be delivered to the engine. Wear may be observed by holding a straightedge against the side of the eccentric and looking for a groove in the center where the pump arm rides. If there is any groove, the eccentric is bad.
Troubleshooting oil circulation: Oil has been used in engine lubrication for a multitude of purposes since the introduction of the internal combustion engine. Original engines were not equipped with a pump-operated, pressurized system. Instead a “dipper” on the crankshaft threw oil onto moving parts and filled the crankcase with a vaporized cloud of oil. Although this technique is effective, modern engine designs rely on oil pressure to maintain an oil wedge between moving parts to prevent friction. The lubricating system uses a low viscosity oil to lubricate, cool, and clean moving parts in the engine. The lubrication system is pressurized at anywhere from 10 psi (pounds per square inch) to 80 psi according to engine speed. The system contains 6 quarts of oil, with a quart or two of oil in constant circulation during engine operation. The lubrication system contains four stages: a filter, an oil circulation pump, a collection and storage sump (oil pan), and oil passageways.
Oil pan: The oil pan (sump) collects and stores all oil not being used in the system. This is the first and last step in the oil circulation process. Oil pan gaskets may fail after extended use, leading to oil leakage. To find the location of an oil leak, carefully clean all around the suspected area and operate the vehicle long enough to reproduce the leak. This will pinpoint the source of the leak.
Oil pump: The oil pump is the second step in the circulation process. Precision gears inside the pump create a vacuum, which sucks oil into the pump. Pressure by the rotating gears against oil on the far side pushes oil into the system. Oil pressure should generally register at least 10 psi for every 1000 revolutions per minute (rpm) that the engine turns. If the pressure registers below this, do not assume that the oil pump is at fault. Internal or external leaks can reduce pressure. A worn pump will cause gradual pressure loss, not immediate loss. Also there should still be a great deal of pressure even if the pump is worn. A pressure gauge measures only how much the system is pressurized, not how quickly oil is currently moving in it. If the system is obstructed, pressure will still be high on the gauge (Adkins, 87). There are several ways to confirm proper pump function. The first is to remove the pump and place the pickup tube in a bucket of clean oil. By rotating the pump drive shaft with a screwdriver, direct diagnosis may be made. The second method involves completely disassembling the pump and examining parts for correct clearances and wear.
Oil galleries and passageways: The oil passageways convey the pressurized oil to the lubrication points in the system. Galleries collect oil from the system and carry it directly back to the sump bypassing the filter. There is a small gallery plug located on the driver’s side rear of the interior of the engine block. Failure to install this plug will result in a massive internal oil leak that will reduce pressure. Cold oil will build up pressure without this plug, but as the oil heats and becomes less viscous the pressure will quickly drop to nothing (Adkins, 141).
Oil filter: Oil carried through the system by the passageways will pass through the filter or return to the sump. Only some of the oil is filtered because of a bypass that allows oil to flow even if the filter is clogged or obstructed. A clogged filter will cause dirty oil, but not reduced pressure. A damaged or loose filter could cause a pressurized leak that will reduce oil volume very quickly because the filter is under system pressure.
Lubrication problems will eventually lead to failure in other parts of the engine. Low oil pressure will increase the rate at which parts wear and lead to early failure, while no oil pressure will result in parts seizing or breaking.
Troubleshooting coolant circulation: Coolant is formulated from a mixture of 50 percent water and 50 percent antifreeze. The cooling system is completely self-contained. The coolant prevents the cast-iron engine block, heads, and intake manifold from overheating by conducting the heat outside of the engine to be dissipated. Coolant always circulates through the engine and pump during engine operation. If there is an external coolant leak, the liquid will turn to steam and produce a sweet smell (SanSone, 218). The cooling system consists of five components: a radiator, a circulation pump, three hoses, a thermostat, and a fan with a clutch.
Radiator: The coolant starts in the radiator where air is passed over metal fins to conduct the heat away. Pinpoint leaks in a radiator will be evident as the coolant changes to steam. Spray may also splash over nearby areas.
Coolant pump: The pump pulls coolant from the radiator with an impeller. Since the pump is always in operation when the engine is running, coolant is in constant circulation at all times during engine operation. If the thermostat is closed, coolant is circulated through the engine only, bypassing the radiator. To check if the coolant pump has seized, remove all accessory belts and attempt to spin the pump drive pulley manually. If the pump binds or does not spin easily, the bearings have seized. Also if the pulley shaft can be rocked inside the bearing, it has worn too much. Extreme pump failure will create a shrill screech during operation with possible leaking of coolant.
Coolant hoses: Coolant is carried from the radiator to the pump and back again by two rubber hoses. There is also a short, small diameter hose that jumps from the front of the engine to the intake manifold. Coolant will collect in low points on the intake manifold if a hose is leaking. Corrosion from evaporated antifreeze will collect on metal around the area of the leak. Gently bending a hose to expose cracked or broken rubber will also find a leak. If the leak is severe, the engine may overheat and smoke from coolant burning off the hot metal surfaces (Styvie, 1-12).
Coolant thermostat: The bimetal thermostat is responsible for limiting coolant flow during cold operation to allow the engine to warm up quickly. Once the engine block has warmed past 195 degrees Fahrenheit, the thermostat opens. The heat of the engine should be maintained within about 195 to 210 degrees during normal operation. Coolant circulates through the block to return to the radiator via the pump. The thermostat may become stuck in either a closed or open position. If it is open, the engine will take longer than usual to warm up. If the thermostat is stuck closed the engine will warm up as usual but overheat severely. To test the thermostat, lower it into a bucket of water heated to about 100 degrees. The thermostat is preset to open at 95 degrees, and should visibly open in the bucket. Seeing whether the upper radiator hose is hot after the engine has been warmed up is another indicator. If the hose is warm, the thermostat has opened because warm water from the engine has passed through the hose.
Fan blades and clutch: The fan is responsible for moving air across the fins of the radiator to dissipate heat. It operates at exactly the same speed as the pump impeller because they are on the same accessory pulley. An overrunning clutch keeps the speed to a predetermined maximum. When the centrifugal force exerted by the spinning fan on the clutch exceeds this maximum, the clutch slips and allows the fan to slow down separate from the pump impeller. If the fan clutch is functioning properly, the fan can be rotated by hand without turning the coolant pump pulley. Broken or bent fan blades will allow engine temperature to increase. A malfunctioning fan will cause the engine to severely overheat at idle and low speeds because air will be forced across the radiator only when the vehicle is moving.
Troubleshooting emissions equipment: The emissions system is designed to prevent un-burnt gases and vapors from entering the atmosphere (Chrysler, 88). In 1987 Dodge Ram models, the system consists of three main items: the re-circulation pump, the evaporation canister, and the exhaust gas re-circulation (EGR) valve. Although there are several small components such as vacuum lines, problems lying in these areas are simple to track down and eliminate.
Air re-circulation pump: The pump circulates improperly burnt exhaust gases and crankcase vapors back into the system at the exhaust manifolds along with fresh air to continue the molecular breakdown of the unused fuel. The air pump will emit a shrill metallic screech if the bearings have failed. To see if the pump is operating correctly, remove the belt and rotate the pulley manually. If it binds or does not turn at all, the pump needs replaced.
Evaporation canister: The evaporation canister is designed to trap fuel vapor, preventing pollution of the atmosphere. If the canister becomes clogged with dirt or debris it will not function correctly. Although no loss of power usually results from a malfunctioning evaporation canister, vehicle emissions will increase. The filter is located inside the canister, and may be examined by removing the plastic cover. Discoloration of the filter element indicates that its functionality is decreased.
Exhaust gas re-circulation (EGR) valve: This vacuum controlled valve opens to allow gases to flow through the re-circulation system. It is affected by engine temperature and will not open below 65 degrees Fahrenheit. The valve may be tested by removing and exposing it to temperature both above and below 65 degrees. If the valve opens, the unit is functioning properly.
Emissions problems will generally result in power loss and an increased pollution level.
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