July 2009 Archives

Direct injection engines -- found in vehicles ranging from sports cars to snowmobiles -- are becoming more common as manufacturers look to improve the internal combustion engine by squeezing out more horsepower, less emissions and better fuel efficiency.

Several GM engine families presently use Spark Ignited Direct Injection (SIDI) technology, including the 2.0L turbocharged 4-cylinder engine in the Saturn SKY and Pontiac Solstice and the 3.6L V6 engine in the Cadillac CTS. (Fig. 1) Some industry projections indicate that in a few years, one in six engines will be built with direct injection. The numbers illustrate the value of the technology: the 300 HP 3.6L V6 in the new Chevy Camaro is rated at an estimated 29 MPG highway.

Direct injection refers to the fact that the fuel is injected directly into the combustion chamber. Direct injection is not new. In fact, it's a basic principle of the diesel engine. A diesel engine depends on the heat of compression to ignite the diesel fuel the instant it's injected into the cylinder (this is Compression Ignited Direct Injection or CIDI). By comparison, SIDI engines inject gasoline directly into the air in the cylinder and the resulting mixture is then ignited by a spark plug. (Fig. 2)

The injection system used on SIDI engines differs from standard fuel injection in one important way. With SIDI, the fuel is injected at a much higher pressure (up to 2,176 psi or 15,000 kPa) because it's injected directly into the combustion chamber rather than into the intake manifold (port injection).

Benefits of SIDI

When compared with port injection, benefits of SIDI include:

- lower emissions, particularly at startup

- higher compression

- better fuel economy (particularly on turbocharged engines)

- increased horsepower

All gasoline engines depend on atomizing the fuel before combustion. But with carburetors, throttle bodies, and even port injection, the atomization takes place at a distance from the combustion chamber. By the time the atomized fuel and air reach the combustion chamber, some of the fuel has separated out and collects on intake surfaces. SIDI eliminates all of this by atomizing the fuel directly in the combustion chamber. As the fuel atomizes, the air and fuel mixture are cooled, enabling the use of a higher compression ratio.

Better atomization contributes to a reduction in pre-ignition and detonation, which is why the SIDI engine can operate at a higher compression ratio and consume less fuel. SIDI allows the engine to run on a leaner mixture (more air, less fuel) at full power. SIDI also allows a higher compression ratio, which in turn provides better fuel economy at part and full throttle.

Direct injection permits controlling a richer mixture around the spark plug, making it easier to ignite when the engine is cold. The SIDI engine runs smoother and generates lower emissions during cold start and warm-up.

Components

The fuel delivery components of SIDI are divided into two groups, the low pressure system and the high pressure system.

Low side components are essentially the same as those in a port injection system. The fuel tank contains a modular reservoir assembly (fuel pump). Fuel pressure in the low side is approximately 60 psi (410 kPa).

Low pressure lines deliver the fuel from the in-tank fuel pump to the engine compartment. (Fig. 3)

A stainless steel pipe, containing the fuel pulse dampener (Fig. 4) and fuel pressure service valve, connects the fuel line to the high pressure pump. The fuel pulse dampener may have an audible clicking sound when the engine is idling.

The high side starts at the high pressure pump (Fig. 5), which is located at the rear of the cylinder head. It is driven by extra lobes on the camshaft. This pump is capable of delivering fuel at a pressure of 2,176 psi (15,000 kPa).

The high pressure pump incorporates the fuel rail pressure (FRP) regulator. The FRP is operated by the ECM, using pulse width modulation, to provide the fuel pressure commanded by the ECM. And the high pressure pump also incorporates a pressure relief valve.

The fuel rail delivers fuel from the pump to the injectors. A fuel pressure sensor is attached to the fuel rail, and it contains a diaphragm and strain gauges. Both the fuel rail and pressure sensor are made of stainless steel. A silicone-free lubricant should be used before mounting the sensor.

Electro-magnetic fuel injectors are used. (Fig. 6) They mount to the cylinder head and spray fuel directly into the combustion chamber. Precision-machined holes generate a cone shaped spray pattern. The injector hold-down clamp must be replaced if removed.

The ECM contains a converter that steps up voltage from 12V to 65V and charges a capacitor. The capacitor provides 65V to open the injector. Then the ECM provides pulse width modulated 12V to hold the injector open for the prescribed time.

SIDI Service Highlights

A scan tool can be used to perform the following (see the appropriate Service Information for details):

- Cylinder Power Balance

- Fuel Injector Balance

- Fuel Pressure Control

- Fuel Pump on/off

- Fuel System High Pressure Reduction

Low side system pressure relief is the same as with standard fuel injection systems.

High side system pressure relief can be done two ways:

- Turn off the engine and wait at least two hours, then cover the high pressure fitting with a shop towel and loosen

- Use a scan tool to command the fuel pump relay off, run the engine until it stops (approximately 30 seconds). Turn off the ignition and confirm fuel pressure with the scan tool.

To remove and service injectors, it may be necessary to use special tools. Check the Service Information for more details about the right tools.

When removing injectors, the following must be discarded and replaced:

- fuel injector hold-down clamps

- O-rings

- plastic spacers

- fuel injector seal

When removing the high pressure fuel pump, the following must be discarded and replaced:

- fuel pump bolts

- fuel pump gasket and O-ring

- high pressure fuel pipe

When installing the high pressure fuel pump, be sure the roller lifter is oriented properly, the camshaft is at base circle, and the number 1 piston is at top dead center (TDC) on the exhaust stroke.

- Thanks to Mike Militello and GM Powertrain

Water pumps move hundreds of gallons of coolant. Eventually, the bearings (Fig. 7, A) and seal (Fig. 7, B) wear out, causing a noise or leak.

Some leakage around the water pump weep hole is evidence of normal coolant weepage, which prevents coolant from accumulating around the bearing seal. This is a normal condition. However, if there is a constant drip or stream out of the weep hole, especially under pressure, the seal may be worn and the water pump needs replacement.

Water pumps also may fail due to contamination and corrosion caused by the lack of proper maintenance or servicing of the cooling system. Failure to flush the cooling system when the water pump or other system components are replaced can leave excessive contamination and lead to repeat failure. (Fig. 8)

Also, if there is a visible wobble in the shaft or the bearings are making noise, the water pump needs to be replaced.

Service Tips

When replacing a water pump, there are several key items to keep in mind in order to complete a successful repair and eliminate a comeback. These include:

- Determine the root cause of failure, especially if the water pump failed prematurely

- Flush the cooling system completely

- Use the recommended 50/50 coolant/water mix

- Do not use any non-approved flush agents

- Follow the instructions that are included with the water pump

- Use sealant tabs if recommended

Engine Coolant

Quality coolant and water are critical to water pump operation. Contaminated coolant, depleted coolant, and poor water quality can result in corrosion and seal damage.

Water quality varies greatly in different areas. Tap water contains chlorine and chloride, which are corrosive to aluminum. Unclean water also leaves mineral deposits in the cooling system, which can reduce coolant flow.

Engine coolants come in various colors and formulations, ranging from conventional green coolants to a variety of long-life coolants that may be orange, red, gold or blue. The color is mainly a dye, but the chemistry of the coolants is different.

Vehicle manufacturers have different coolant requirements and there may be some confusion over which type of coolant to use in a vehicle. Check the Service Information for the correct coolant for the vehicle being serviced. Most manufacturers do not recommend mixing long-life coolant and conventional coolant. New coolant may be degraded if the correct 50/50 coolant/water mix is not used or if there are excessive contaminants in the system.

When replacing a water pump, it's critical to flush the cooling system. Prior to performing the flush procedure, remove, clean and reinstall the coolant recovery reservoir. To flush the system, use power flush equipment or thermal cycle the system with clean water three times.

Installation

After installing the new water pump, perform the following to ensure a proper repair:

- Torque the bolts to the manufacturer's specifications

- Adjust belts to the proper tension (if applicable)

- With the new pump installed, turn the hub by hand and check for rotation

- Pressure test the system for leaks

Ever since production ended in 2002, Camaro enthusiasts have been anxiously awaiting the return of their favorite pony car. Well, the wait is over.

The 2010 Camaro (Fig. 9) returns with all the classic styling cues -- the prominent grille with recessed headlamps, the SS front air scoop, the gills on the rear quarters, dual exhaust outlets, and even the auxiliary instrumentation on the console. Here's a closer look behind the retro-inspired sheet metal of the new Camaro.

Performance

The base engine is the 3.6L (LLT) VVT direct injected DOHC V6. With variable valve timing and dual overhead camshafts, it generates 304 HP (227 kW) and 273 lb-ft (370 Nm) of torque.

In addition to direct injection, advanced features of the engine include variable valve timing, roller chain cam drive, and piston cooling jets for lower temperature and increased durability.

For those wanting more power, there are two versions of the 6.2L OHV V8. In cars with an automatic transmission, the V8 (L99) offers 400 HP (298kW) and 410 lb-ft (556 Nm) of torque. (Fig. 10) With a manual transmission, the V8 (LS3) offers 426 HP (318 kW) and 420 lb-ft (569 Nm) of torque. The L99 engine also comes with Active Fuel Management that shuts down four cylinders based on driving conditions for better fuel economy. All feature aluminum block and heads.

Two 6-speed manual transmissions are available with either the V6 or V8 engine. The available 6-speed automatics -- the 6L50 transmission on the V6 and the 6L80 transmission on the V8 -- feature TAPshift, which enables the transmission to be shifted manually with steering wheel paddles. Performance Algorithm Liftfoot (PAL) detects performance driving and holds upshifts and downshifts. Additionally, the 6L80 on V8s has an internal cooler.

Handling

On V8 models, the StabiliTrak electronic stability control system includes a Competitive Mode that limits StabiliTrak and ABS intervention for competitive driving venues.

V8 models with a manual transmission also offer Vehicle Launch Control, which uses traction control and torque management to minimize wheelspin and optimize straight-line acceleration. When the accelerator pedal is pressed to the floor with the clutch engaged, the RPM is limited to a predetermined level. Releasing the clutch while keeping the accelerator pedal pressed to the floor provides controlled wheelspin and acceleration.

Four-wheel discs are provided with ABS, ranging from 12.6-inch front and 12.4-inch rear discs, vented with 1-piston calipers, on LS/LT models and 14-inch front and 14.4-inch rear discs, vented with Brembo 4-piston calipers, on SS models. (Fig. 11)

Wheels and tires range from 18 to 20 inches, including summer tires on SS models. It is highly recommended that owners purchase winter tires if they plan to drive the Camaro SS in winter.

Interior

The Camaro has a number of unique interior features. It uses a window indexing feature to help eliminate wind noise. The windows open slightly when the door is opened, and then move back to the closed position when the door is closed. This feature must be reset if battery power is disconnected.

Auxiliary analog gauges on the console (certain models) include oil pressure, battery voltage, oil temperature and transmission fluid temperature. (Fig. 12)

The heavy duty battery, with rundown protection and retained accessory power, is located in the trunk, contributing to the 52%/48% weight distribution. The accessory power outlets shut down when the vehicle is turned off to further enhance the rundown protection capability.

- Thanks to Marty Case and Chris Graham

The move of independent repair facilities toward OEM scan tools has been gaining momentum in the last few years, driven mainly by the increased complexity of vehicle networks and the lack of software coverage from traditional aftermarket scan tools. Many ACDelco TSS shops have invested in the Vetronix/Bosch Tech 2, which has been the OEM scan tool in General Motors dealerships worldwide since 1997. Saab has been using the Tech 2 in their franchised dealerships since the late 1990's, but the software has been difficult to obtain in the aftermarket until now.

With the introduction of TIS2Web in late 2007, available via www.acdelcotechconnect.com, independent service centers can now purchase OEM diagnostic software for Saab to be used in their Tech 2. Software coverage spans from 1988 to the current model year and covers the 900, 9000, 9-3, 9-5 and 9-7X models.

Tech 2 software coverage includes full OEM powertrain, chassis and body systems, including recoding, output controls and customer configuration settings. A quick system check allows the technician to request DTCs from all vehicle control modules in less than ten seconds, dramatically decreasing diagnostic time and increasing repair productivity. (Fig. 13)

There are three separate software loads required for full Saab coverage, so shops must purchase additional 32MB PCMCIA cards if support for the entire product line is desired. For shops that currently own a Tech 2 with the 32MB PCMCIA card loaded with GM North American software, the 9-7X model is already included, since it shares a platform with the Chevrolet TrailBlazer and GMC Envoy. The remaining models are on two separate software loads, requiring two additional 32MB PCMCIA cards.

Authentic GM 32MB PCMCIA cards (part number 02002994-001) can be purchased directly from Bosch Diagnostics customer support at 1-800-321-4889. The Saab 10-pin DLC connector (part number 02002965), required for 1995-older vehicles, also is available.

Software can be purchased on an annual subscription basis and includes Saab Service Programming reflashing software with current calibrations. Saab Service Information also can be purchased on an annual subscription basis from www.acdelcotechconnect.com.

- Thanks to Bob Augustine

Voltage drop is the reduction in voltage in an electrical circuit between the source and load. Another way to look at it is the difference in voltage potential between two points.

A voltage drop check is a more accurate indication of the condition of a circuit than a resistance check. Imagine a 12-gauge wire with all but one strand of wire cut. The circuit would have good continuity if checked with a Digital Multimeter (DMM), but once current was forced through the circuit, it would undoubtedly fail.

There will always be a certain amount of voltage drop in any electrical circuit. This is because voltage is lost as it passes through a conductor due to the resistance of the conductor. However, excessive voltage drop in a circuit on either the power or ground side will result in poor operation of electrical components as less voltage is available to operate the load. In fact, electrical motors may be damaged by excessive voltage drop.

When performing voltage drop checks, the circuit being tested must be operational. With the positive lead of the DMM connected to one point of the circuit and the negative lead connected to the other point, operate the circuit to get the difference in voltage between the two points. (Fig. 14)

When checking the integrity of a ground circuit, use the best ground on the vehicle -- the battery's negative post. Likewise, when checking the circuit's power side, use the battery's positive post as the starting point. Generally, anything over a 0.5 volt drop on either the power or ground side is considered excessive drop for most circuits, but always refer to published Service Information for exact specifications.

- Thanks to Mike DeSander

Registered vehicles in the U.S. now outnumber licensed drivers. That means more vehicles with more technology coming into automotive service centers today and in the future. It's also why there continues to be a growing need for automotive technicians. Each year, the Bureau of Labor Statistics lists the need for automotive technicians as one of the nation's highest.

Finding qualified technicians is getting tougher. As vehicles have become increasingly complex, the skills and specialized training needed by the next generation of technicians to repair them can't be picked up at the local gas station or in high school shop class.

One way to successfully recruit new technicians is through the GM Automotive Service Educational Program (ASEP).

GM ASEP is designed to bring TSS accounts together with qualified students who want to pursue a career as an automotive technician. ASEP students attend classes for eight to ten weeks at a college that participates in the program. Then the students work in their sponsoring service center for a similar period of time. In addition to automotive courses, ASEP students take courses in math, science, and communication skills. During the two-year sponsorship, service centers are responsible for providing uniforms, paying an hourly wage while working in the shop, and assigning a technician to act as a mentor to the student.

At the end of the program, the student graduates with an Associate Degree in automotive technology and the TSS service center has a new technician who has trained at the shop and also has knowledge of the latest diagnostic procedures, equipment, and information technology.

Looking for a student to sponsor? An ASEP college will provide a list of qualified candidates for an interview. The first step is to contact the participating college in your area. There are more than 60 ASEP schools in the country. For the complete list of ASEP colleges, go to www.gmasep.com, or call 1-800-828-6860.

Student and Service Center Responsibilities

Students:

- Must be high school graduates and accepted into a participating college

- Must maintain a TSS service center sponsorship

- Are required to wear a provided work uniform during school and at work

- Are responsible for all program costs, including tuition, fees, books and tools. Tuition assistance and tool discounts may be available.

Service Centers:

- Must pay for uniforms

- Must pay the student an hourly wage while providing work experience in accordance with the program schedule

- Must provide an in-shop coordinator

- Must participate in the appropriate ASEP advisory committee meetings

- Thanks to Staci Shelton

ACDelco has recently introduced a new, improved low Volatile Organic Compound (VOC) non-chlorinated brake parts cleaner, part number 10-6012. This product replaces part number 10-111.

The new brake parts cleaner is specially formulated to remove oil, grease, brake fluid, dirt and contaminants from brake components, including brake shoes, drums, springs, brake plates, calipers, pads and rotors. It's also an effective cleaner for clutch, transmission and engine parts.

- Thanks to Mike DeSander

Summer 2009 Testing (Fig. 15)

Registration Window: July 10 - August 15

Testing Window: July 17 - August 22

For information, visit www.ase.com/cbt

Toll-free registration: 1-800-525-6929

The following technical tips provide repair information about specific conditions on a variety of vehicles. If you have a tough or unusual service repair, the TSS Technical Assistance Hot Line can help. Call 1-800-825-5886, prompt #2, to speak with a technical expert with the latest OEM information.

Service Charging System Message on DIC

2005-2009 Chevrolet Corvette; 2004-2009 Cadillac XLR

A Service Charging System message may be displayed on the Driver Information Center (DIC) along with a stored DTC P0621. This condition may be a result of aftermarket spark plugs or an open in circuit number 2540.

Check for aftermarket spark plugs. Plugs that are designed with a "pulse" technology may interfere with this circuit and cause the Service Charging System message in the DIC and/or P0621 DTC to store in the ECM. If aftermarket plugs are installed, replace the plugs with OEM parts.

Also, try the horn to see if it works. If the horn does not work, suspect an open fuse. Circuit 2540 is supplied voltage from the horn fuse, position 2 in the UBEC. This fuse may open if the horn is shorted due to water intrusion.

If the horn is functional, check the integrity of circuit 2540 between the UBEC and the generator. Refer to the appropriate Service Information. Repair circuit 2540 as needed.

V Engine Cylinder Bank Naming

GM vehicles equipped with a V engine

GM uses two methods of naming cylinder banks in V engines.

For emission related components, cylinder banks are named using a Society of Automotive Engineers (SAE) recommended practice. Bank 1 is the cylinder bank that has the number 1 cylinder, and bank 2 is the cylinder bank that does not have cylinder 1. Cylinder 1 location is given in Service Information category Engine Mechanical.

For other than emission related components, cylinder banks are named Left and Right. This is determined by looking toward the front of the engine from the flywheel end. This method is used whether the engine is installed longitudinally or transversely.

Brake Pad Cracks

2007-2009 Chevrolet Silverado 3500HD; 2007-2009 GMC Sierra 3500HD -- with brake RPO JK4 or JH7

When performing a brake inspection on a 2007-09 Chevrolet Silverado 3500HD or GMC Sierra 3500HD with brake RPO JK4 or JH7, hairline cracks may be noticed in the pad friction material. (Fig. 16)

Cracks in the friction material can occur after the pads have been subjected to high pad temperatures.

These hairline cracks do not affect the operation of the brake system and the pads should not be replaced if only hairline cracks are found.

Battery Charging Precautions

1995-2007 Mazda B-Series;1997-2003 Mazda Protégé; 1997-2005 Mazda Miata; 1997-2002 Mazda 626; 1997-2002 Mazda Millenia; 1997-2006 Mazda MPV; 2001-2006 Mazda Tribute; 2003-2007 Mazda6; 2004-2007 Mazda3; 2004-2007 Mazda RX-8; 2006-2007 Mazda5; 2006-2007 Mazda MX-5; 2007 Mazda CX-7

When attempting to re-charge a fully discharged battery, remove it from the vehicle. If a sulphated battery is charged in the vehicle with the battery cables connected and the charger is set to the high charge setting, excessive voltage produced by the charger may result in damage to the Powertrain Control Module, audio system, memory back-up circuits and other electrical devices. Damage may also occur to other electrical components that are activated or that are in use while the battery is being charged in the vehicle.

The maximum voltage for vehicle electrical components is approximately 15 volts. Battery chargers generate at least 15 volts, and in some cases, as much as 20 volts under the high charge setting.

Discharged Battery, Slow Starting

1997-1998 Buick Skylark; 1997-1998 Chevrolet Cavalier and Malibu; 1997-1998 Oldsmobile Achieva and Cutlass; 1997-1998 Pontiac Grand Am and Sunfire - with 2.2L, 2.4L, 3.1L engines (RPOs LN2, LD9, L82)

The battery may be weak or discharged, the starting motor may turn slowly, or the generator may not be charging.

Check for a loose generator output and battery positive cable terminal at the starting motor. This may cause a high resistance in the battery positive circuit from the generator to the battery. Also inspect the condition of the starting motor B+ stud, wire, ring terminals and nut.

If these conditions are found, the generator and battery should not be damaged and will not require replacement.

A new fuel filter (12633243/TP3012) (Fig. 17) is now available for all 2001-2009 Chevrolet and GMC C/K models and 2003-2009 Chevrolet and GMC C4500/5500 series vehicles with the 6.6L Duramax Diesel. It has been designed to offer better protection in engines that may use an unreliable fuel source with potential water conditions.

Compared to the existing dual pleat design filter, the new coalescer filter provides the following improvements:

-      Significantly improved water separation with both diesel and biodiesel blended fuels to protect fuel injectors and pumps from corrosion.

-      1.5 to 2 times the contaminant capacity, depending on the type of contaminants in the fuel. (Longer life/less prone to plugging problems and better performance at high altitudes.)

-      Improved resistance to cold weather plugging with diesel and biodiesel improperly blended or additized for cold operation.

Please note that the new fuel filter (12633243/TP3012) will be shipped in boxes labeled with a different part number (98081884/TP3012) until the current inventory of boxes is exhausted.

For more information, refer to ACDelco Bulletin #09D-068.

- Thanks to Mike Militello

Go to www.acdelcotechconnect.com and click on the Training tab to log on to the ACDelco Learning Management System (LMS).

New Training