Fix It

While the computerized engine management systems that run todays cars are extremely complex and require increasing specialized diagnostic equipment and tools, all gasoline-burning engines must still have spark plugs. The plugs allow a properly timed spark of electricity to jump through the flammable mixture introduced into the top of the piston chamber, causing ignition. Ascertaining their condition is done more through familiarity and interpretive knowledge than through the use of a single piece of equipment.

Know Your Plugs

The terms cold plug and hot plug are often used, and a knowledge of what to expect from the plug is necessary in determining its condition. The terms er to the ability of the material that the plug is made from to transfer heat, in this instance from the point at which the spark occurs into the engine block for dissipation. A cold plug transfers heat quickly and does not work well at extremely high temperatures. A hot plug transfers heat poorly, allowing heat to build up to approximately 1,550 degrees Fahrenheit, and is designed to work in that way; hot plugs are less susceptible to fouling because they burn off contamination. Identification is a question of experience: In general, hot plugs have longer insulator tips.

Visual Condition

Always allow an engine to fully cool before attempting any service work, including the removal of spark plugs. If the insulator tip of a plug that has been in service looks pale gray, or pale gray with a yellow or brown tint, the engine is running correctly, the spark plug gap is set correctly and the plug is torqued correctly into the receiver. Dull, black carbonization on the tip suggests that too-cold plugs are in use, and they should be replaced with hotter-running units. As with all visual indications, this symptom could also indicate problems elsewhere in the engine, in this instance a bad fuel mixture. Melting at the electrode indicates either that the plug was incorrectly torqued into position or that the heat range of the plug is not as suggested for the engine.

Gapping

The space between the electrode and the insulator tip must be exact for the plug to function correctly. Spark plug gap-testing tools are a set of wafer-thin blades -- each blade looks something like a fingernail cleaner -- that rotate on a pivot in and out of a case. These tools used to be ubiquitous in every do-it-yourselfers and professionals kit, but modern engines and plug technology have made them all but redundant. New plugs are now delivered with the gap precisely set and do not deform under any but the most extreme of engine conditions. If a modern spark plug gap changes under use, that is a symptom, not a cause; the cause must be determined by engine diagnostics and the plug set replaced after rectification of the fault.

Equipment

An array of equipment is available to test spark plug condition, but the visual checks suggested and a regular maintenance schedule make the investment practically unnecessary, even for the professional. The spark plug gapping tool is, as noted, all but redundant in modern vehicle maintenance practices. Working according to the manufacturers instructions, it is possible to use a volt-ohmmeter to ascertain the circuit load.

Voltage Testing

Metered spark gap testers are available that plug into the coil to measure the jump of the spark. Capable of handling current between 0 and 40,000 volts, the tool diagnoses faults in the coil, the ignition wires and the plugs.

Testing Spark Plug Wires

Inline spark testers that use a bulb do not give a metered reading, but they do give an instant indication of whether a coil-wire-plug circuit is operational. The device is inserted between the plug and the wire, after you have first removed the wire from the top of the plug. When the engine is turned over a bulb flashes if the circuit is functional but does not flash if it is faulty. Compact ignition testers are extremely simple to use to verify that there is a spark to the plug. Fitted into a plug wire end and clamped to the engine, they should spark when the engine is turned over. If they do not, there is a problem upstream of the device.

2001 Chevrolet Silverados use a hub-mounted wheel sensor system that consists of an electro-magnetic sensor and a notched reluctor wheel on each front wheel. The reluctor wheel spins at the same RPM as the wheel and the electro-magnetic sensor records this information in pulses. The PCM and ABS computers decode this information and use it determine wheel speed. By determining the wheel speed, both computers can tell if a wheel is locked up or spinning faster than the other. In order to diagnose a faulty wheel sensor, you must monitor the data stream with a scan tool and also confirm that each sensor is receiving voltage.

Instructions

1

Lift the front portion of vehicle with a jack and support it with jack stands; both front tires must be at least 6-inches off of the ground. Place wheel chocks behind the rear wheels and apply the parking brake.

2

Switch the ignition to the ON position and connect a scan tool to the trucks data port under the dashboard below the steering wheel. Navigate to the live data menu and monitor the wheel speed sensors; they should both read zero.

3

Turn on the engine and lightly depress the throttle while monitoring the scan tool. The wheel speed sensor output readings should match the speedometer output. If one sensor does not then it is most likely faulty.

4

Turn off the engine but leave the ignition on and lie down on a mechanics creeper. Roll underneath the car and examine the wheel speed sensor wires for fraying or cuts.

5

Unplug the connector from the wheel speed sensor. Probe the light blue wire for the left-front wheel sensor and the tan wire for the right-front wheel sensor with a digital multimeter. The specified voltage value is 1.8 to 12 volts. If the multimeter reads less than 1.8 volts then find and repair the short in the wire and retest the sensor. If the voltage reading is within specification then replace the wheel speed sensor.

Your engine needs to be able to build and hold a great deal of compression in the combustion cylinders in order to operate properly. Additionally, compression in each of the cylinders needs to be within a small percentage range from highest to lowest. Compression can leak past one or both of the valves, which can be detected by a noticeable hissing sound in the exhaust or intake. Compression can also leak past the head gasket seals into the cooling system. This kind of leak needs to be found and fixed quickly, before it causes serious internal damage to your engine.

Instructions

1

Disconnect the spark plug wires at the plugs by gripping the plug and twisting while turning. Write the cylinder number on the plug boot to facilitate reassembly.

2

Rotate the spark plugs counterclockwise with the spark plug socket and ratchet to remove them. Use extensions and universal swivel as needed.

3

Thread the leakdown tester into the opening for the first spark plug. Remove the radiator cap by pressing down and turning it counterclockwise. Add the exhaust gas detector solution to the radiator coolant. Place the balloon or rubber glove over the radiator opening.

4

Turn the key to start and allow the engine to turn over about 10 times.

5

Check the glove or balloon to see if it appears to have filled at all. If so, you have determined there is a leak from the combustion chamber into the cooling system from number one cylinder. Write down the compression reading.

6

Repeat Steps 3, 4 and 5 until you have checked all of the cylinders in turn, checking the balloon/glove after each time you turn the engine over. Write down each of the compression readings.

7

Compare the compression readings from cylinder to cylinder. The reading should be around 150 pounds per square inch of compression, with a maximum variance of about 15 pounds per square inch from high to low readings.

8

Remove the balloon or glove from the radiator opening and inspect the coolant. Some exhaust gas leak kits will cause the coolant to change color in the presence of exhaust gasses. Others will have you look at the coolant using a special light.

Various parts of the car have electrical needs that are provided by the cars battery, which includes the headlights, ignition coils, engine cooling system, the radio and the air conditioner. Like with all electronic devices, the alternator can be tested using specialized equipment known as an alternator tester. These alternator testers can determine what is wrong with a particular alternator so that the problems can be fixed. Testers are especially important when initially designing the alternator so that engineers can ensure that the alternator will work in all operating conditions.

Bench Testers

Alternator bench testers must simulate the actual operating conditions of the load testers. Speed control is handled electronically when simulating the operating conditions, according to Crumbliss, a company specializing in alternator testers. Alternator testers come in many varieties. What distinguishes them is their horsepower, which ranges from five to 20; whether or not they are single or three-phase; if they have electronic variable speed; their voltage, which ranges from 12 to 32; their amperage, which ranges from 65 to 450; and their wattage, which ranges from 2100 to 7200. Horsepower is a measurement of the testers power, voltage is the amount of electrical current generated by the alternator tester, and wattage is the electrical power of the tester.

Heavy Duty Testers

There is also the heavy duty load tester that tests 12- and 24-volt automotive and diesel starters. Other heavy duty power supply testers are available that test alternating and direct currents, according to Crumbliss. These testers deliver 500 amps of constant voltage, adequate for testing powerful alternators.

Performance and Endurance Testers

Alternator performance and endurance testers have PC-based PID controllers, which are generic feedback mechanisms. The alternator speed can be adjusted electronically. They have loading in constant resistance, current and voltage modes, according to Samin Afzar company, a company that specializes in test machines for cars. They have a temperature chamber that subjects the alternator to a specific temperature that is adjustable so that certain conditions can be simulated. They have an instant 500 voltage in loading machines.

Wires Used With Testers

Wires must be connected to the coils inside the alternator so that there is an easy connection between the testing equipment and the circuits. According to All About Circuits, a company specializing in electrical wiring, the alternator often has to be taken apart so that the wires can be connected to terminals, called carbon brushes, found within the alternator. The wires are soldered to the terminals then run through the vent holes on the alternator. The wires must be run in a way that will not cause the wires to be caught by the spinning rotor.

Although diesel fuel injectors perform using greater pressures than gasoline injectors, they are still prone to the same issues. Diesel fuels with low sulfur are actually more likely to cause issues with fuel injectors than regular gasoline. Having information on the equipment used to test for problems with a vehicles injectors can be beneficial to automobile owners.

Significance

Fuel injectors can suffer clogging issues from deposits left behind from the diesel fuel. Heavy wear, as well as leaks, are things for which vehicle owners should check. Diesel fuel also fails to provide proper lubrication, which can cause the fuel to not flow though the injectors as smoothly as it should.

Pyrometer

One type of test equipment that can be used to check diesel fuel injectors is called a digital pyrometer. Each engine cylinders temperature is revealed when using a digital pyrometer, indicating the specific cylinder thats not up to par. Low temperatures in one cylinder often means a problem with fuel injection.

Ohmmeter

Another type of test equipment used for checking fuel injectors in diesel engines is an ohmmeter. The ohmmeter tests the resistance of glow plugs as their resistance rises according to engine temperature. Because of this, a low glow plug resistance reading means no heat is being produced from a particular cylinder. This in turn can indicate injector issues.