🏷️ Basic Information

Make:

Porsche

Model:

928 S

Model Year:

1985

Generation:

Second Generation (928 S)

Internal Model Code:

Type 928

👋 Introduction

Historical Significance:

The Porsche 928 was a groundbreaking luxury grand tourer from Porsche, featuring a front-engine, rear-transaxle layout and V8 power, differentiating it from the marque's traditional rear-engine sports cars.

Market Segment:

Competed with other high-performance GT cars of its era, such as the Jaguar XJS, Aston Martin V8 Vantage, and potentially lower-end Ferrari models.

Model Year Highlights:

The 1985 model year introduced significant updates to the S model, often including improved engine performance and refinement over earlier versions.

Usefulness For Owners:

Essential for diagnosing and repairing complex electrical issues common in sophisticated European cars of this era, particularly for owners seeking to maintain originality or undertake DIY repairs.

Usefulness For Technicians:

Indispensable tool for independent repair shops and Porsche specialists working on the 928.

📋 Manual Details

Primary Coverage:

Electrical System Wiring Diagrams

Secondary Coverage:

Component Integration and Location

Estimated Page Count:

Varies by specific publication; typically 50-150 pages for a dedicated wiring diagram manual.

Manual Type:

Wiring Diagram Manual / Electrical Troubleshooting Manual

Language:

English (Standard for this market)

Format:

Likely Printed Booklet or Digital PDF

📖 Manual Coverage

Lighting System:

Headlamps (High/Low Beam), Tail Lamps, Brake Lamps, Turn Signals, Parking Lamps, Fog Lamps, Interior Lighting (Dome, Map, Glovebox, Ash Tray).

Body Electrical:

Power Windows, Power Door Locks, Central Locking System, Mirrors (Power Adjustment/Defrost), Wipers (Front/Rear), Washers, Horn, Sunroof/Moonroof Operation (if equipped).

Instrument Cluster And Indicators:

Speedometer, Tachometer, Fuel Gauge, Oil Pressure Gauge, Coolant Temperature Gauge, Oil Temperature Gauge, Voltmeter, Warning Lamps (Brake, Oil Pressure, Charging System, ABS, Airbag - if equipped), Turn Signal Indicators, High Beam Indicator.

HVAC System:

Blower Motor, Heater Core Control Valve, Air Conditioning Compressor Clutch, Mode Selector Controls, Temperature Control System (manual or automatic climate control specific wiring).

Audio System:

Factory Radio/Cassette Player Wiring, Amplifier Connections (if applicable), Speaker Wiring.

Safety Systems:

Anti-lock Braking System (ABS) Module and Sensor Wiring, Alarm System Wiring, Trailer Coupling Electrical Interface (if factory option).

Engine Electronics:

Digital Engine Electronics (DME) Harnesses, Fuel Injection System Wiring, Ignition System Wiring, Sensors (Crankshaft Position, Camshaft Position, Throttle Position, Knock, Lambda/Oxygen), Fuel Pump Control, Idle Control Valve.

Central Electrical System:

Fuse Boxes, Relay Locations and Function, Battery Connections, Grounding Points, Power Distribution.

Troubleshooting Guidance:

Interpreting Circuit Diagrams, Identifying Wire Colors and Functions, Locating Components, Common Fault Diagnosis based on electrical symptoms.

Component Location:

Diagrams showing the physical location of fuses, relays, control modules, sensors, and actuators.

Wiring Repair:

Guidance on proper splicing, connector repair, and wire harness maintenance (though often implied through diagram clarity).

Detail Level:

High-Level Detail: Comprehensive circuit diagrams with wire colors, pin assignments, component identification, and connector views.

Diagnostic Focus:

Primarily focused on electrical system diagnostics and repair, not mechanical repairs.

System Interconnectivity:

Illustrates how different electrical systems interface with each other.

📊 Manual Specifications

Digital Format Quality:

If PDF, expect high-resolution scans of original factory diagrams, ensuring clarity and readability.

Printed Format Quality:

Typically printed on durable paper stock with clear line work and legible text.

Printed Binding:

Often spiral-bound or saddle-stitched for ease of use when laid flat.

Printed Paper Type:

Durable paper stock, often with a matte finish to reduce glare.

⚙️ Engine Specifications

Engine Type:

V8, naturally aspirated

Displacement:

4.7 Liters (4664 cc)

Engine Code Variant:

M28/10 (approximate for 1985 S models, specific variants exist)

Horsepower:

Approximately 250-280 hp (SAE net, depending on market and specific tune)

Torque:

Approximately 295-330 lb-ft (SAE net, depending on market and specific tune)

Fuel Delivery:

Bosch L-Jetronic Fuel Injection

Fuel Type:

Premium Unleaded Gasoline

Ignition Type:

Distributorless Ignition System (DIS) with Electronic Control Unit (ECU)

🔧 Transmission

Transmission Type:

5-Speed Manual Transaxle

Transmission Type:

3-Speed Automatic Transaxle (e.g., Automatic Transaxle Model 090)

Layout:

Rear Transaxle (clutch and gearbox located at the rear axle)

Manual Transmission Fluid:

Porsche spec. G 50 (or equivalent GL-4) Gear Oil, typically 75W-90 or 80W-90.

Automatic Transmission Fluid:

Dexron II or III (or equivalent)

📐 Dimensions

Length:

Approx. 179.9 inches (4570 mm)

Width:

Approx. 71.1 inches (1806 mm)

Height:

Approx. 50.0 inches (1270 mm)

Wheelbase:

Approx. 98.4 inches (2500 mm)

Curb Weight:

Approx. 3,500 - 3,700 lbs (1588 - 1678 kg), depending on transmission and options.

Gross Vehicle Weight Rating:

Approx. 4,450 lbs (2018 kg)

🛡️ Safety Features

Historical Safety Testing:

While formal crash test ratings (like NHTSA or IIHS) were less standardized in the early 80s, the 928 was engineered with a strong safety cell and considered a very safe vehicle for its era. ABS was a significant safety feature.

Braking System:

Four-wheel Disc Brakes, Ventilated Front Discs. Standard ABS (Anti-lock Braking System) on '85 models.

Suspension Stability:

Porsche's proprietary 'Weissach Axle' rear suspension designed to improve stability under braking and cornering.

Airbags:

Driver's side airbag was becoming available/standard on some later models, but may not have been standard on all '85 US-market cars. The manual would clarify.

Seat Belts:

Three-point Inertia-reel seat belts

Chassis Construction:

High-strength steel unibody construction

💡 Technology Features

Audio System:

Factory-installed Porsche AM/FM stereo with cassette player. Amplifier systems were often optional. Speaker configurations varied.

Climate Control:

Manual air conditioning and heating system, with some models featuring automatic climate control (ACC) which has its own complex electrical interface.

ABS System:

Bosch ABS II system (or similar iteration) was a significant technological feature for 1985, improving braking safety. Wiring for this system is detailed in the manual.

Lighting Control Logic:

Complex electrical logic for headlamp operation (pop-up headlights), interior lighting delays, and warning chimes.

🔧 Maintenance

Oil Change Interval:

Typically every 5,000-7,500 miles or annually. Consult specific owner's manual for exact interval.

Timing Belt Replacement:

Crucial for V8 engines. Typically every 30,000-60,000 miles or 4-5 years, as it is an interference engine. This manual will not cover this procedure, but it's vital context.

Major Service Items:

Spark Plugs, Air Filter, Fuel Filter, Coolant Flush, Brake Fluid Flush, Transmission Fluid and Filter (auto).

Engine Oil Capacity:

Approx. 8.5 Liters (8.9 US Quarts) with filter change.

Engine Oil Type:

Synthetic SAE 15W-50 or 5W-50 (depending on climate and specific Porsche recommendations for the era).

Coolant Type:

Porsche approved coolant (typically a glycol-based coolant with corrosion inhibitors), often a blue or green color. Capacity around 12 Liters.

Brake Fluid Type:

DOT 4 or DOT 5.1

Electrical Challenges:

Age-related degradation of wiring insulation, connector corrosion, failing relays, sensor issues (e.g., ABS sensors), and HVAC control module failures are common. This manual is key to addressing these.

Mechanical Considerations:

Timing belt, water pump, fuel lines, and suspension components (especially bushings) are common wear items. While not covered here, understanding these informs electrical system interactions.

📚 Vehicle History

Porsche Philosophy:

Porsche is renowned for its engineering prowess, performance-oriented vehicles, and racing heritage. The 928 was an ambitious project to expand the brand's offerings beyond the iconic 911.

928 Development:

Developed as a potential 911 successor, the 928 featured a transaxle design for optimal weight distribution and a front-mounted V8 engine, a significant departure for Porsche.

928 S Introduction:

The 'S' designation introduced in 1978 (and revised for later years like '85) brought increased displacement, higher horsepower, and aesthetic updates like revised front and rear spoilers and larger wheels.

Production Period:

1978-1995

Manufacturing Location:

Stuttgart, Germany

🏆 Awards & Recognition

Historical Acclaim:

The Porsche 928 was lauded by automotive press for its advanced engineering, performance, and luxury, though its unique styling and front-engine layout garnered mixed reactions initially compared to the 911's legacy.

Import Car Of The Year:

The Porsche 928 was named Motor Trend's Import Car of the Year for 1978.