Automotive Engine Performance Tools

Diagnostic and special tools for the air, fuel, ignition, emission, and engine-control systems are discussed in the following paragraphs. This discussion does not cover all of the tools you may need; rather, these tools are the most commonly used by the service industry.

Some are also used when diagnosing or servicing the controls of other automotive systems. Details of when and how to use these tools are covered in here, as well as in other sections where necessary.

++++ A Genysis scan tool.

++++ Various scan tool connectors for OBD-II systems.

++++ Using a scan tool during a road test.

SPX Service Solutions

Scan Tools

A scan tool is a microprocessor designed to communicate with the vehicle's computer. Connected to the computer through diagnostic connectors, a scan tool can access diagnostic trouble codes (DTCs), run tests to check system operations, and monitor the activity of the system. Trouble codes and test results are displayed on a screen or printed out on the scanner printer.

The scan tool is connected to specific diagnostic connectors on the vehicle. Some manufacturers have one diagnostic connector. This connects the data wire from each computer to a specific terminal in this connector. Other manufacturers have several diagnostic connectors on each vehicle, and each of these connectors may be connected to one or more computers. The scan tool must be programmed for the model year, make of vehicle, and type of engine.

With OBD-II, the diagnostic connectors (commonly called data link connectors, or DLCs) are located in the same place on all vehicles. Also, any scan tool designed for OBD-II will work on all OBD-II systems; therefore, the need to have designated scan tools or cartridges is eliminated. Most OBD-II scan tools have the ability to store, or "freeze," data during a road test and then play back this data when the vehicle is returned to the shop.

There are many different scan tools available.

Some are a combination of other diagnostic tools, such as a lab scope and graphing multimeter. These may have the following capabilities:

¦ Retrieve DTCs.

¦ Monitor system operational data.

¦ Reprogram the vehicle's electronic control modules.

¦ Perform systems diagnostic tests.

¦ Display appropriate service information, including electrical diagrams.

¦ Display TSBs.

¦ Display troubleshooting instructions.

¦ Perform easy tool updating through a personal computer (PC).

Some scan tools work directly with a PC through uncabled communication links, such as Bluetooth.

Others use a Personal Digital Assistant (PDA). These are small hand-held units that allow you to read DTCs, monitor the activity of sensors, and view inspection/maintenance system test results to quickly determine what service the vehicle requires. Most of these scan tools also have the ability to:

¦ Perform system and component tests.

¦ Report test results of monitored systems.

¦ Exchange files between a PC and a PDA.

¦ View and print files on a PC.

¦ Print DTC/freeze frame.

¦ Generate emissions reports.

¦ View IM/Mode 6 information.

¦ Display relative TSBs.

¦ Display full diagnostic code descriptions.

¦ Observe live sensor data.

¦ Update the scan tool as a manufacturer's inter faces change.

++++ An engine analyzer.

++++ A fuel pressure gauge and adapters.

++++ A fuel injection balance tester.

Engine Analyzers

When performing a complete engine performance analysis, an engine analyzer is used. An engine analyzer houses all of the necessary test equipment. With an engine analyzer, you can perform tests on the battery, starting system, charging system, primary and secondary ignition circuits, electronic control systems, fuel system, emissions system, and engine assembly. The analyzer is connected to these systems by a variety of leads, inductive clamps, probes, and connectors. The data received from these connections is processed by several computers within the analyzer.

Most engine analyzers have both manual and automatic test modes. In the manual modes, any single test, such as cylinder compression or generator output, can be performed. When the automatic test mode is selected, specific tests are automatically per formed in a specific sequence.

The analyzer may compare the test results to the vehicle manufacturer's specifications. When the test series is completed, the analyzer prints a summary report. Many analyzers also provide diagnostic assistance for the problems indicated by their measurements.

Fuel Pressure Gauge

A fuel pressure gauge is essential for diagnosing fuel injection systems. These systems rely on very high fuel pressures, from 35 to 70 psi. A drop in fuel pressure reduces the amount of fuel delivered to the injectors and results in a lean air-fuel mixture.

A fuel pressure gauge is used to check the discharge pressure of fuel pumps, the regulated pressure of fuel injection systems, and injector pressure drop.

This test can identify faulty pumps, regulators, or injectors and can identify restrictions present in the fuel delivery system. Restrictions are typically caused by a dirty fuel filter, collapsed hoses, or damaged fuel lines.

Some fuel pressure gauges also have a valve and outlet hose for testing fuel pump discharge volume.

The manufacturer's specification for discharge volume is given as a number of pints or liters of fuel that should be delivered in a certain number of seconds.

CAUTION! While testing fuel pressure, be careful not to spill gasoline. Gasoline spills may cause explosions and fires, resulting in serious personal injury and property damage.

Injector Balance Tester

The injector balance tester is used to test the injectors in a port fuel injected engine for proper operation. A fuel pressure gauge is also used during the injector balance test. The injector balance tester contains a timing circuit, and some injector balance testers have an off-on switch. A pair of leads on the tester must be connected to the battery with the correct polarity. The injector terminals are

disconnected, and a second double lead on the tester is attached to the injector terminals.

The fuel pressure gauge is connected to the Schrader valve on the fuel rail, and the ignition switch should be cycled two or three times until the specified fuel pressure is indicated on the pressure gauge.

When the tester push button is depressed, the tester energizes the injector winding for a specific length of time, and the technician records the pressure decrease on the fuel pressure gauge. This procedure is repeated on each injector.

If the pressure drops very little, or if there is no pressure drop, the injector's orifice is restricted or the injector is faulty. If there is an excessive amount of pressure drop, the injector plunger is sticking open.

Sticking injector plungers may result in a rich air-fuel mixture.

! WARNING! Electronic fuel injection systems are pressurized, and these systems require depressurizing prior to fuel pressure testing and other service procedures.

Injector Circuit Testlight

A special testlight called a noid light can be used to determine if a fuel injector is receiving its proper

voltage pulse from the computer. The wiring harness connector is disconnected from the injector and the noid light is plugged into the connector. After disabling the ignition to prevent starting, the engine is turned over by the starter motor. The noid light will flash rapidly if the voltage signal is present.

No flash usually indicates an open in the power feed or ground circuit to the injector.

Fuel Injector Cleaners

Fuel injectors spray a certain amount of fuel into the intake system. If the fuel pressure is low, not enough fuel will be sprayed. Low pressure may also occur if the fuel injector is dirty. Normally, clogged injectors are the result of inconsistencies in gasoline detergent levels and the high sulfur content of gasoline. When these sensitive fuel injectors become partially clogged, fuel flow is restricted. Spray patterns are altered, causing poor performance and reduced fuel economy.

The solution to a sulfated and/or plugged fuel injector is to clean it, not replace it. There are two kinds of fuel injector cleaners. One is a pressure tank. A mixture of solvent and unleaded gasoline is placed in the tank, following the manufacturer's instructions for mixing, quantity, and safe handling. The vehicle's fuel pump is disabled and, on some vehicles, the fuel line must be blocked between the pressure regulator and the return line. Then, the hose on the pressure tank is connected to the service port in the fuel system. The inline valve is then partially opened and the engine is started. It should run at approximately 2,000 rpm for about 10 minutes to clean the injectors thoroughly.

An alternative to the pressure tank is a pressurized canister in which the solvent solution is premixed.

Use of the canister-type cleaner is similar to this procedure but does not require mixing or pumping. The canister is connected to the injection system's servicing fitting, and the valve on the canister is opened.

The engine is started and allowed to run until it dies.

Then, the canister is discarded.

Fuel Line Tools

Many vehicles are equipped with quick-connect line couplers. These work well to seal the connection but are nearly impossible to disconnect if the correct tools are not used. There is a variety of quick-connect fit tings and tools.

++++ A set of noid lights and a test spark plug.

++++Various fuel line disconnect tools.

++++ Pinch-off pliers closing off a vacuum hose.

++++ A vacuum/pressure tester used to measure engine vacuum.

Pinch-Off Pliers

The need to pinch off a rubber hose is common during diagnostics and service. Special pliers are designed to do this without damaging the hose. These pliers are much like vise-grip pliers in that they hold their position until they are released. The jaws of the pliers are flat and close in a parallel motion. Both of these features prevent damage to the hose.

Vacuum Gauge

Measuring intake manifold vacuum is another way to diagnose the condition of an engine. Manifold vacuum is tested with a vacuum gauge. Vacuum is formed on a piston's intake stroke. As the piston moves down, it lowers the pressure of the air in the cylinder-if the cylinder is sealed. This lower cylinder pressure is called engine vacuum. If there is a leak, atmospheric pressure will force air into the cylinder and the resultant pressure won’t be as low. The reason atmospheric pressure enters is simply that when ever there is a low and high pressure, the high pressure always moves toward the low pressure. Vacuum is measured in inches of mercury (in. Hg) and in kilopascals (kPa).

To measure vacuum, a flexible hose on the vacuum gauge is connected to a source of manifold vacuum, either on the manifold or at a point below the throttle plates. The test is made with the engine cranking or running. A good vacuum reading is typically at least 16 in. Hg. However, a reading of 15 to 20 in. Hg (50 to 65 kPa) is normally acceptable.

Since the intake stroke of each cylinder occurs at a different time, the production of vacuum occurs in pulses. If the amount of vacuum produced by each cylinder is the same, the vacuum gauge will show a steady reading. If one or more cylinders are producing different amounts of vacuum, the gauge will show a fluctuating reading.

Vacuum Pump

There are many vacuum-operated devices and vacuum switches on cars. These devices use engine vacuum to cause a mechanical action or to switch something on or off. The tool used to test vacuum actuated components is the vacuum pump. There are two types of vacuum pumps: an electrical-operated pump and a hand-held pump. The hand held pump is most often used for diagnostics. A hand-held vacuum pump consists of a hand pump, a vacuum gauge, and a length of rubber hose used to attach the pump to the component being tested. Tests with the vacuum pump can usually be performed without removing the component from the vehicle.

When the handles of the pump are squeezed together, a piston inside the pump body draws air out of the component being tested. The partial vacuum created by the pump is registered on the pump's vacuum gauge. While forming a vacuum in a component, watch the action of the component. The vacuum level needed to actuate a given component should be com pared to the specifications given in the factory service manual.

++++36 Typical hand-operated vacuum pump with accessories.

++++37 A digital timing light. Courtesy of SPX Service Solutions

The vacuum pump is also used to locate vacuum leaks by connecting the vacuum pump to a suspect vacuum hose or component and applying vacuum. If the needle on the vacuum gauge begins to drop after the vacuum is applied, a leak exists somewhere in the system.

Vacuum Leak Detector

A vacuum or compression leak might be revealed by a compression check, a cylinder leakage test, or a manifold vacuum test. However, finding the location of the leak can often be very difficult.

A simple, but time-consuming, way to find leaks in a vacuum system is to check each component and vacuum hose with a vacuum pump. Simply apply vacuum to the suspected area and watch the gauge for any loss of vacuum. A good vacuum component holds the vacuum applied to it.

Another method of leak detection is done by using an ultrasonic leak detector. Air rushing through a

vacuum leak creates a high-frequency sound higher than the range of human hearing. An ultrasonic leak detector is designed to hear the frequencies of the leak. When the tool is passed over a leak, the detector responds to the high-frequency sound by emitting a warning beep. Some detectors also have a series of light emitting diodes (LEDs) that light up as the

frequencies are received. The closer the detector is moved to the leak, the more LEDs light up or the faster the beeping occurs, allowing the technician to zero in on the leak. An ultrasonic leak detector can sense leaks as small as 1/500 inch and accurately locate the leak to within 1/16 inch.

Tachometer

A tachometer is used to measure engine speed. Like other meters, tachometers are available in analog and digital types. Digital meters are the most common.

Tachometers are connected to the ignition system to monitor ignition pulses, which are then converted to engine speed by the meter.

Several types of inductive pickup tachometers that simplify rpm testing are available. An inductive tachometer simply clamps over the number 1 spark plug wire. The digital display gives the engine rpm, based on the magnetic pulses created by the secondary voltage in the wire. This type of tachometer is suit able for distributorless ignition systems.

Timing Light

A timing light is used to check ignition timing. The timing light is connected to the battery terminals and has an inductive clamp that fits over the number 1 spark plug wire. While the engine is running, the timing light emits a beam of light each time the spark plug fires. Many timing lights have a timing advance knob that may be used to check spark advance. Some timing lights electronically measure timing advance as the engine rpm is increased and displays it on an LED display.

Spark Tester

A spark tester is a fake spark plug.

The tester is constructed like a spark plug but does not have a ground electrode. In place of the electrode there is a grounding clamp. Using test spark plugs is an easy way to determine if the ignition problem is caused by something in the primary or secondary circuit.

The spark tester is inserted in the spark plug end of an ignition cable. When the engine is cranked, a spark should be seen from the tester to a ground. Experience with these testers will also help you determine the intensity of the spark.

Logic Probes

In some circuits, pulsed or digital signals pass through the wires. These on-off digital signals either carry information or provide power to drive a component.

Many sensors, used in a computer-controlled circuit, send digital information back to the computer. To check the continuity of the wires that carry digital signals, a logic probe can be used.

A logic probe is similar in appearance to a test light. It contains three different-colored LEDs. A red LED lights when there is high voltage at the point being probed. A green LED lights to indicate low volt age. A yellow LED indicates the presence of a voltage pulse. The logic probe is powered by the circuit and reflects only the activity at the point being probed.

When the probe's test leads are attached to a circuit, the LEDs display the activity.

If a digital signal is present, the yellow LED turns on. When there is no signal, the LED is off. If voltage is present, the red or green LEDs will light, depending on the amount of voltage. When there is a digital signal and the voltage cycles from low to high, the

yellow LED will be lit and the red and green LEDs will cycle, indicating a change in the voltage.

Sensor Tools

Oxygen sensors are replaced as part of the preventive maintenance program and when they are faulty.

Because they are shaped much like a spark plug with wires or a connector coming out of the top, ordinary sockets don’t fit well. For this reason, tool manufacturers provide special sockets for these sensors.

Special sockets are also available for other sending units and sensors.

Static Strap

Because electronic components are sensitive to volt age, static electricity can destroy them. Static straps are available for technicians to wear while working on or around electronic components. These straps typically are worn around a wrist and connected to a known good ground on the vehicle. The straps send all static electricity to the ground of the vehicle, thereby eliminating the chance of this electricity going to the electronic components.

++++38 A heated oxygen sensor socket.

++++39 A hand-held digital infrared temperature gauge.

++++40 A spark plug socket.

++++41 A five-gas exhaust analyzer.

Pyrometers

The converter should be checked for its ability to convert CO and HC into CO2 and water by doing a delta temperature test. To conduct this test, use a hand held digital pyrometer ( ++++39). By touching the pyrometer probe or placing it near to the exhaust pipe just ahead of and just behind the converter, there should be an increase of at least 100°F or 8% above the inlet temperature reading as the exhaust gases pass through the converter. If the outlet temperature is the same or lower, nothing is happening inside the converter. A pyrometer can also be used to measure the temperature of the coolant at various stages of its travel.

Spark Plug Sockets

Special sockets are available for the installation and removal of spark plugs. These sockets are deep sockets with a hex nut drive at the end to allow a technician to turn them with a ratchet or an open-end wrench. The sockets are available in the common sizes of spark plugs (5/8-inch, 9/16-inch, and 13/16-inch) and have a 3/8-inch drive. The socket is built with a rubber sleeve that surrounds the insulator part of the spark plug to prevent cracking or other damage to the plug while it’s being removed or installed.

++++A "MicroGas" five-gas exhaust analyzer.

Exhaust Analyzers

Federal laws require that new cars and light trucks meet specific emissions levels. State governments have also passed laws requiring that owners maintain their vehicles so that the emissions remain below an acceptable level. Most states require an annual emissions inspection to meet that goal. Many shops have an exhaust analyzer for inspection purposes.

Exhaust analyzers are also very valuable diagnostic tools. By looking at the quality of an engine's exhaust, a technician is able to look at the engine's combustion process and the efficiency of the vehicle's emission controls. Any defect will cause emission levels to increase. The amount and type of change is considered during diagnostics.

Exhaust analyzers measure the amount of HC and CO in the exhaust. HC is measured in parts per mil lion (ppm) or grams per mile (g/mi) and CO is measured as a percent of the total exhaust. In addition to measuring HC and CO levels, an exhaust analyzer also monitors CO2 and O2 levels. Many exhaust analyzers also measure a fifth gas, oxides of nitrogen (NOx).

By measuring NOx, CO2, and O2, in addition to HC and CO, a technician gets a better look at the engine's efficiency. There is a desired relationship among the five gases. Any deviation from this relationship can be used to diagnose a driveability problem.

Chassis Dynamometer

A chassis dynamometer, commonly called a dyno, is used to simulate a road test. A vehicle can be driven through a wide assortment of operating conditions without leaving the shop. Because the vehicle is stationary, test equipment can be connected and monitored while the vehicle is driven under various loads.

This is extremely valuable when diagnosing a problem. A chassis dyno can also be used for performance tuning.

The vehicle's drive wheels are positioned on large rollers. The electronically controlled rollers offer rotational resistance to simulate the various loads a vehicle may face.

Some performance shops have an engine dynamometer that directly measures the output from an engine. A chassis dynamometer measures the engine's output after it has passed through the driveline.

Hybrid Tools

A hybrid vehicle is an automobile and as such is subject to many of the same problems as a conventional vehicle. Most systems in a hybrid vehicle are diagnosed in the same way as well. However, a hybrid vehicle has unique systems that require special procedures and test equipment. It’s imperative to have good information before attempting to diagnose these vehicles. Also, make sure you follow all test procedures precisely as they are given.

Gloves Always wear safety gloves when working on or around the high-voltage systems. These gloves must be class "0" rubber insulating gloves, rated at 1,000 volts (these are commonly called

"lineman's gloves"). Also, to protect the integrity of the insulating gloves, as well as you, wear leather gloves over the insulating gloves while doing a service.

CAUTION! The condition of the gloves must be checked before each use. Make sure there are no tears or signs of wear. Electrons are very small and can enter through the smallest of holes in your gloves. To check the condition of the gloves, blow enough air into each one so they balloon out. Then fold the open end over to seal the air in. Continue to slowly fold that end of the glove toward the fingers. This will compress the air.

If the glove continues to balloon as the air is compressed, it has no leaks. If any air leaks out, the glove should be discarded. All gloves, new and old, should be checked before they are used.

Test Equipment An important diagnostic tool is a DMM. However, this is not the same DMM used on a conventional vehicle. The meter used on hybrids (and EVs and FCEVs) should be classified as a category III meter. There are basically four categories for low-

voltage electrical meters, each built for specific purposes and to meet certain standards. Low voltage, in this case, means voltages less than 1,000 volts. The categories define how safe a meter is when measuring certain circuits. The standards for the various categories are defined by the American National Standards Institute (ANSI), the International Electrotechnical Commission (IEC), and the Canadian Standards Association (CSA). A CAT III meter is required for testing hybrid vehicles because of the high voltages, three-phase current, and the potential for high transient voltages. Transient voltages are voltage surges or spikes that occur in AC circuits. To be safe, you should have a CAT III 1000 V meter. A meter's voltage rating reflects its ability to withstand transient voltages.

Therefore, a CAT III 1000 V meter offers much more protection than a CAT III meter rated at 600 volts.

++++ A pair of lineman's gloves. 600V CAT III EN6101 EN61010-1 -1

++++Only meters with this symbol should be used on the high-voltage systems in a hybrid vehicle.

!WARNING! Always follow the test procedures defined by the manufacturers when using their equipment.

Another important tool is an insulation resistance tester. These can check for voltage leakage through the insulation of the high-voltage cables. Obviously no leakage is desired and any leakage can cause a safety hazard as well as damage to the vehicle. Minor leakage can also cause hybrid system-related drive ability problems. This meter is not one commonly used by automotive technicians but should be for anyone who might service a damaged hybrid vehicle, such as doing body repair. This should also be a CAT III meter and may be capable of checking resistance and voltage of circuits like a DMM.

To measure insulation resistance, system voltage is selected at the meter and the probes placed at their test position. The meter will display the voltage it detects. Normally, resistance readings are taken with the circuit de-energized unless you are checking the effectiveness of the cable or wire insulation. In this case, the meter is measuring the insulation's effectiveness and not its resistance.

The probes for the meters should have safety ridges or finger positioners. These help prevent physical contact between your fingertips and the meter's test leads.

Next: Transmission / Driveline Tools

Prev.: Electrical/Electronic System Tools