The Fiat 312 B1.000 is a 1,998 cc, inline-four, naturally aspirated petrol engine produced between 2003 and 2008. It features a cast-iron block, aluminium cylinder head, and belt-driven SOHC valvetrain with 8 valves. In standard tune, it produces 88 kW (120 PS) at 5,500 rpm and 170 Nm of torque at 3,500 rpm, delivering smooth performance for mid-size passenger vehicles during the early 2000s.
Fitted to core Fiat models including the Stilo (188), Doblò (223), and Marea (185), the 312 B1.000 was engineered for improved refinement, fuel efficiency, and emissions compliance over earlier units. It utilised sequential multipoint fuel injection (Magneti Marelli IAW 59) and a three-way catalytic converter to meet Euro 3 standards (Directive 98/69/EC), with closed-loop lambda control ensuring stable idle and low hydrocarbon emissions.
One documented service concern is premature camshaft belt wear, particularly in high-temperature climates or vehicles with extended service intervals. This issue was addressed in Fiat Service Information Bulletin 03-16, which reinforced replacement intervals and specified updated belt material. Later production units (post-2005) incorporated a revised automatic tensioner design and improved coolant routing, reducing thermal stress on the timing cover.
All production models meet Euro 3 emissions standards (Directive 98/69/EC, VCA UK Type Approval #VCA/EMS/9124).
The Fiat 312 B1.000 is a 1,998 cc inline-four, naturally aspirated petrol engine designed for compact and mid-size passenger vehicles (2003–2008). It combines SOHC valvetrain architecture with sequential multipoint fuel injection to deliver smooth, responsive performance. Designed to meet Euro 3 emissions standards, it balances drivability with improved serviceability over earlier units.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,998 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 83.6 mm | |
| Power output | 88 kW (120 PS) @ 5,500 rpm | |
| Torque | 170 Nm @ 3,500 rpm | |
| Fuel system | Magneti Marelli IAW 59 sequential multipoint injection | |
| Emissions standard | Euro 3 | |
| Compression ratio | 9.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Rubber toothed belt (SOHC, front-mounted) | |
| Oil type | SAE 10W-40, API SL | |
| Dry weight | 142 kg |
The SOHC 8-valve design offers predictable performance and ease of maintenance but requires strict adherence to 60,000 km cam belt replacement intervals to prevent valve damage. Use of SAE 10W-40 oil meeting API SL standards ensures adequate valve train lubrication under sustained load. Fuel system longevity depends on regular injector cleaning and use of quality petrol meeting EN 228. Post-2005 models benefit from a revised automatic belt tensioner and coolant routing; pre-2005 units should be inspected per Fiat SIB 03-16. Lambda sensor degradation is common beyond 120,000 km, leading to increased fuel consumption if not replaced.
Oil Specs: Requires SAE 10W-40, API SL specification (Fiat SIB 03-16). Compatible with ACEA A3/B3 standards.
Emissions: Euro 3 certification applies to all models (2003–2008) under Directive 98/69/EC (VCA Type Approval #VCA/EMS/9124).
Power Ratings: Measured under ECE R85. Output varies slightly based on ignition timing and air filter condition (Fiat TIS Doc. B31218).
Fiat Technical Information System (TIS): Docs B31201, B31218, SIB 03-16
VCA Type Approval Database (VCA/EMS/9124)
EU Directive 98/69/EC: Amendments to Emissions Standards
The Fiat 312 B1.000 was used across Fiat's Stilo/Doblò platforms with transverse mounting and shared architecture with Lancia variants. This engine received platform-specific adaptations—reinforced mounts in the Doblò and revised intake manifolds in the Stilo—and from 2005 the facelifted Stilo Active used a revised ECU mapping and secondary air injection, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the exhaust manifold (Fiat TIS B31205). The 8th VIN digit indicates engine type ('H' for 312 B1.000 series). Pre-2005 models have a black plastic intake manifold with a round airbox; post-2005 units use a revised rectangular plenum. Critical differentiation from diesel variants: Petrol 312 B1.000 uses a red-painted fuel rail and Magneti Marelli IAW 59 ECU, while diesel units (312 D1.000) have a black fuel rail and Bosch injection system. Service parts require model-year verification—cam belts for pre-2005 models are not compatible with later automatic tensioner units (Fiat SIB 03-16).
The 312 B1.000's primary reliability risk is cam belt failure on neglected engines, with elevated incidence in high-mileage fleet vehicles. Internal Fiat service data from 2004 indicated a significant share of pre-2005 engines suffering belt-related damage beyond 75,000 km, while UK DVSA records show timing-related failures as a leading cause of MOT rejection for classic models. Extended service intervals and aftermarket non-compliant belts increase risk, making adherence to replacement schedules critical.
Analysis derived from Fiat technical bulletins (2003-2008) and UK DVSA failure statistics (2004-2013). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 312-B1-000.
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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