Checking ignition systems and electrical equipment
1. Turn on the ignition and make sure that the indicator lamp on the instrument panel lights up properly.
2. Turn on the starter and check the stability of the engine cranking.
3. Turn on the headlights and check the intensity of their glow.
4. If the headlights do not light up, or the starter does not crank the engine, proceed as follows:
- Disconnect the wires from the battery and strip both terminals and terminal clamps (see accompanying illustration). Reconnect the wires and securely (but not excessive) tighten the clamps.
Note. With poor contact, the terminals usually warm up noticeably after several start attempts.
- Check the condition and reliability of the fastening of the battery grounding tires to the engine, the engine to the frame. Also check the tire contacts for signs of oxidation and contamination.
- Check the condition of the wire from the battery to the starter, as well as the external condition of the starter traction relay. Also check that the wire terminals are clean and secure.
- Repeat the checks of the first three paragraphs of the subsection. If the starter still does not crank the engine or the lights do not come on, one of the following situations is possible.
Starter or lights not working
- The battery is defective or discharged.
Headlights are on but starter is not working
- The battery fuse has failed.
Starter drive is stuck in engagement with flywheel ring gear
- Faulty starter relay.
- Faulty ignition switch.
- On models with AT, the starter circuit disconnect switch, fuse or relay is faulty.
The headlights are dimmed and the starter turns too slowly
- The battery is discharged or the starter motor is defective.
- The battery is discharged due to a broken or slipped alternator drive belt. One or more cans in the battery burst.
Contact Breaker Models
1. Set the gap between the serviceable type replacement spark plug to 6 mm. Securely ground the spark plug body with a jumper wire (see accompanying illustration), or by holding the spark plug firmly to a securely grounded point on the engine block (tie it with string or tape). Remove the spark plug wire and connect it to this test spark plug.
2. Ask the assistant to include a starter.
3. A spark should jump between the electrodes of the test plug. If there is no spark, or it is yellow and weak, proceed to the procedure in the next paragraph. If the spark is strong enough, skip the checks below.
4. Disconnect the wire of the ignition coil from the distributor cap and bring it to the test candle. Repeat the above test. If a strong spark of bright blue color forms on the candle, the cause of the failure lies in the malfunction of the distributor cap, its runner, the rev limiter switching screen or the spark plug wire. If there is still no spark, turn off the ignition and perform the following checks:
- Check the condition of the spark plug wires (see accompanying illustration), - they must be dry and without cracks in the insulation.
- Check the distributor cap for moisture and dirt. Inspect the inside surfaces of the cover and distributor speed limiter screen for cracks and carbon tracks (see accompanying illustration), paying special attention to the areas between the contact segments of the spark plugs in the cover and the electrodes in the screen.
- Check the distributor slider for cracks, dirt deposits and burnouts of the metal spout. Make sure that the spring for limiting the rotation of the slider button is in place and that the spring is in good condition (the accompanying illustration shows a runner spring test on a 4.2L model).
- Check the cleanliness, dryness and reliability of fastening in the distributor cover of the contact connections of the cross-section wires and the ignition coil.
- Make sure the carbon brush in the center of the inside surface of the distributor cap is dry and clean.
- Check the condition and reliability of the fastening of the HB wires on the ignition coil. Make sure there are no signs of oxidation of their terminals.
- Make sure that electrical current reaches the coil when the ignition is turned on. Use a test lamp by connecting it between the HB positive terminal of the coil and a well grounded point (see accompanying illustration). Make sure the breaker contacts are open, or insulate them with dielectric tape during this test. If the test lamp lights up when connected to the side of the coil facing the ignition lock and does not light up when connected to the side facing the contact breaker, then the possibility of damage to the primary winding of the coil cannot be ruled out. Remove the coil or test it by swapping it with a known good one.
- Check the condition of the breaker contacts, clean and adjust if necessary.
- Check the condition and reliability of the distributor ground wires.
- Repeat check. If there is still no spark, or a weak yellow spark, one of the following failures is possible.
The lamp does not light
There is an open circuit between the ignition switch and the positive terminal of the coil. Again, using a probe lamp, make sure that power is supplied to the ignition switch and the HB connector of the engine wiring harness.
Note. If a probe lamp is not available, the LV wire can be disconnected from the side of the coil facing the ignition lock and brought to a securely grounded point in order to check for current. Similarly, the second LV wire can be disconnected from the distributor and grounded to check for current. During the verification of point g) make sure that the breaker contacts are open (isolated), and the ignition is on (key - in the ON position).
Faulty coil, capacitor or spark plug wires
A coil failure is indicated by severe burnout or breaker contacts or the presence of deep cavities on them - replace the capacitor and breaker contacts.
If, during the above checks and correction of the identified defects, it is possible to achieve a spark of sufficient efficiency, but the engine still does not start, remove all spark plugs and check their condition and the size of the interelectrode gaps.
Models with electronic ignition
1. Set the gap between the serviceable type replacement spark plug to 6 mm. Ground the spark plug body securely with a jumper wire, or by pressing the spark plug firmly to a securely grounded point on the engine block (tie it with string or tape). Remove the spark plug wire and connect it to this test spark plug.
Attention! When working with an electronic ignition system or near its components, certain precautions must be observed, associated with the risk of electric shock when in contact with the elements of the explosive primary and secondary circuits of the system.
Turn off the ignition before disconnecting or connecting any components of the electronic system to avoid electric shock and damage to the ignition system.
2. Ask the assistant to include a starter.
3. A spark should jump between the electrodes of the test plug. If there is no spark, or it is yellow and weak, proceed to the procedure in the next paragraph. If the spark is strong enough, skip the checks below.
4. Disconnect the wire of the ignition coil from the distributor cap and bring it to the test candle. Repeat the above test. If a strong spark of bright blue color forms on the candle, the cause of the failure lies in the malfunction of the distributor cap, its slider, rev limiter screen or spark plug wire. If there is still no spark, turn off the ignition and perform the following checks:
- Check the condition of the BB spark plug wires - they must be dry and without cracks in the insulation.
- Check the distributor cap for moisture and dirt. Inspect the inside surfaces of the cover and distributor speed limiter screen for cracks and carbon tracks (see accompanying illustration), paying special attention to the areas between the contact segments of the spark plugs in the cap and the electrodes in the rev limiter screen.
- Check the distributor slider for cracks, dirt deposits and burnouts of the metal spout. Make sure that the spring for limiting the rotation of the slider button is in place and that the spring is in good condition (the accompanying illustration shows a rotor spring test on a 4.2L model).
- Check the cleanliness, dryness and reliability of fastening in the distributor cover of the contact connections of the cross-section wires and the ignition coil.
- Make sure the carbon brush in the center of the inside surface of the distributor cap is dry and clean.
Note. Further checks of the electronic ignition system should not be carried out, as they carry the risk of electric shock as a result of the high voltage present in the primary and secondary circuits of the system. The rules for performing procedures are described in the Section on the electronic ignition system.
5. If in the course of performing the above checks and correcting the identified defects, it is possible to achieve a spark of sufficient efficiency, but the engine still does not start, remove all spark plugs and check their condition and the size of the interelectrode gaps.
Checking the power system
Assuming there is fuel in the gas tank, the first check should be to check for the presence of fuel in the carburetor float chamber. On carburetors equipped with a sight glass, visually check the presence of fuel in the chamber. The fuel level should reach the middle of the viewing window.
To perform the following check, remove the air cleaner assembly and look into the carburetor neck with the choke open. Keeping your eyes on the throat, open and close the throttle a few times by moving its rod with your hand. If fuel is injected through the discharge nozzle of the accelerator pump when the throttle valve is moving, this means that the float chamber is full and the power system is functioning properly (see accompanying illustration).
If injection does not occur, proceed as described below.
1. Disconnect the ignition coil HB connector to prevent accidental starting of the engine during the test.
2. Disconnect the fuel supply hose from the carburetor and lower it into a drain pan. Have an assistant run the starter a few times and watch the fuel push out of the hose. If the fuel splashes into the container properly, skip the procedures described in the next three paragraphs, if not, proceed to these procedures.
3. Disconnect the hoses and remove the fuel filter from the engine compartment. Make sure the filter is blowing in both directions. If necessary, replace it. Install a working filter in place, securely fastening the hoses with clamps.
4. On 4.2L models, disconnect the fuel supply line from the gas tank from the inlet side of the fuel pump. Remove the fuel filler cap and have an assistant listen for sounds coming from the filler neck. Blow into the fuel line towards the gas tank. If the patency of the line is not broken, the assistant will hear a gurgling in the tank.
Note. The test described above cannot be performed on 3.0L models, as they are equipped with an electric fuel pump built into the gas tank equipped with a one-way control valve. If the fuel supply does not return after cleaning the fuel filter, refer to the Power System Section for more information and perform the appropriate electrical fuel pump function check.
5. Connect the fuel line to the fuel pump and check the fuel supply from the pump. If there is no fuel supply to the carburetor side of the pump, one of the following failures is possible.
Models 3.0 l
- Fuel pump defective.
- The fuse has been blown.
- Faulty wiring.
- The control unit has failed.
- The patency of the fuel lines is broken.
Models 4.2 l
- Gurgling in the tank when blowing the gas line is not audible
- The patency of the fuel line is broken, or there is a break.
- Fuel intake strainer clogged.
Gurgling occurs, but there is no fuel supply from the pump
Fuel pump defective. See the relevant section on pump troubleshooting.
If fuel is properly supplied to the fuel line from the carburetor side, and the engine still does not start, perform the following checks:
1. Make sure that the carburetor has not flooded due to excessively intensive swinging of the gas pedal when trying to start. Also make sure the choke is not stuck in the closed position when the engine is warmed up to normal operating temperature. The consequences of a carburetor flood can sometimes be eliminated by tapping on the float chamber in the area where the needle valve and its seat are located (see accompanying illustration).
2. Remove the spark plugs and check that the electrodes are not flooded with fuel. If necessary, thoroughly wipe and dry the spark plugs before reinstalling them.
3. If carburetor flooding occurs, check needle valve float for signs of jamming. Also check to see if the float is broken, which led to filling it with fuel.
4. Check for clogged air cleaner element.
5. If the carburetor does not flood, and the fuel is regularly supplied to it, the possible causes of failure are the following:
- Fuel filter blocked.
- Stuck or blocked needle valve.
- Check valve not closing properly.
- There are air leaks in the intake manifold or through the carburetor support flanges due to deformation or destruction of the gaskets.
- Broken vacuum brake booster hose or loose connection between booster and intake manifold.
Late Years 4.2L Models Equipped with Fuel Injection (EFI)
Note. Due to the complexity of the design of EFI systems, the compilers of this Guide recommend that the reader, if the following checks do not reveal the cause of the failure (engine still won't start), refer to the relevant section on diagnostics of malfunctions of fuel injection systems and engine management below in this chapter.
1. Make sure there is enough fuel in the gas tank.
2. Pinch the fuel supply hose in the area in the middle between the fuel filter and the fuel line (see accompanying illustration) and ask an assistant to turn on the ignition. The fuel pump relay should make a distinctly audible click, and palpable pulsations should appear in the hose, indicating that the fuel pump is supplying fuel properly. When ambient noise levels are low, you may also hear a buzzing sound through the fuel filler neck from the pump for about five seconds after the ignition is turned on.
3. If the relay clicks but the pump does not function, check the 15 amp fuel pump fuse in the relay box in the vehicle's engine compartment. If the fuse is OK, check for supply voltage at the pump terminals when the ignition is turned on for five seconds.
4. If the relay does not click when the ignition is turned on, replace it.
5. If the fuel pump functions properly, but the pressure in the fuel hose does not rise, check the patency of the fuel lines and filter. If, after eliminating all the identified defects, the engine still does not start, remove the spark plugs and check them for traces of fuel on the electrodes. Rinse and dry the spark plugs thoroughly before reinstalling them. If the candles do not fill, but the engine still does not start, refer to the Section on diagnostics of malfunctions of fuel injection systems and engine management below in this chapter.
Checking mechanical systems
The procedures described below should be followed if the starter turns the engine over normally. Otherwise, depress the clutch to disengage the engine from the gearbox (models with manual transmission).
If the starter still cannot crank the engine, then the cause of the failure is not a transmission fault - remove the starter and try to crank the engine by hand. Such a check will determine whether the cause of the failure lies in the jamming or failure of the starter, or there is a mechanical failure of the internal components of the engine, such as connecting rod and piston assemblies, crankshaft, etc. If the starter is OK and the engine does not crank by hand, refer to the Section on diagnosing the causes of mechanical engine failures below.
It should be remembered that the only correct way to check the compression pressure in the engine cylinders is to check using a compression gauge. The compression ratio test method described below provides only a rough estimate of the overall mechanical condition of the engine.
1. Remove the radiator cap and check the coolant level in it. If the level drops too low, carefully inspect the power package for signs of external leaks. Remove the dipstick for measuring the level of impellent oil, and inspect its blade for signs of oil foaming (see accompanying illustration). If the oil on the dipstick blade has a milky consistency, while increasing its level, skip the following three steps and proceed to perform further checks.
2. De-energize the ignition system by disconnecting the positive wire from the ignition coil.
3. Turn out all spark plugs, except for one.
4. Turn on the starter and listen for the sounds of the cranking engine. Alternately rearrange the candle in different cylinders, repeating the check. The sound produced by the operation of a cylinder with reduced compression will be noticeably different to the ear. In addition, a serviceable cylinder will create a noticeable resistance to cranking the engine, while cranking the engine with a spark plug installed in the cylinder with reduced compression will occur freely.
5. If the above checks reveal coolant leaks and traces of coolant in the engine oil or on the spark plugs, check the condition of the cylinder head gasket, inspect the block and for cracks, and measure the flatness of the mating surfaces of the head with the block.
6. If the compression ratio test reveals a weakening or uneven distribution of compression pressure, a piston defect should be added to the list of possible causes listed in the previous paragraph (to her) and burnt or defective valve (ov).
7. If the above checks show no signs of internal coolant leaks, continue the diagnostic procedure by performing the checks below.
8. Remove the cover from the ignition distributor and make sure that when the starter is on, the distributor slider rotates synchronously with the engine.
9. Remove the cylinder head cover and with the starter turned on, the valves open and close properly as the engine cranks.
10. Further, if the slider or valves do not function properly, the options listed below are possible.
The slider does not rotate, but the valves function properly
- The distributor drive gear or its shaft is cut off.
Slider and valves do not function
- There is a defect in the camshaft or timing belt (3.0 l) /chain (4.2 l).
If during the correct execution of all the above checks no deviations from the norm were detected, it remains only to check the correctness of the ignition timing and valve timing. However, it should be noted that if the cause of the failure is a violation of the ignition timing, it is necessary to find out the cause of this violation, especially if the engine started and functioned properly until the last moment.
Note. To check the setting of the ignition timing and valve timing, it is necessary to remove the distributor caps and cylinder heads and turn the engine clockwise by the crankshaft pulley so that the piston of the first cylinder is in the TDC position of the end of the compression stroke. In this case, the valves of the first cylinder should be closed, and the distributor slider should turn its nose to the segment BB of the spark plug wire of the first cylinder in the distributor cap.