The Fiat 138 A5.000 is a 1,498 cc inline-four petrol engine produced between 1980 and 1984. It was developed as a modernized powerplant for the Fiat 138 compact sedan, delivering 59–64 kW (80–87 PS) depending on application. Equipped with a single overhead camshaft (SOHC), 8-valve head, and single or twin-choke carburettor (Weber 32/34 IDF or 34 DMTR), it offered improved fuel efficiency and smoother operation over previous Fiat four-cylinder units.
Fitted to the Fiat 138 and 138 S models, the A5.000 was engineered for urban and regional driving, targeting private and fleet users seeking reliability and ease of service. Its design emphasized emissions compliance and mechanical simplicity, with secondary air injection and exhaust gas recirculation (EGR) enabling adherence to ECE Regulation 15 Phase II standards. The engine featured a belt-driven camshaft and lightweight aluminium cylinder head.
A documented engineering update occurred in 1982, referenced in Fiat Service Bulletin 82-ME-01, introducing revised EGR valve calibration and improved intake manifold sealing. This addressed reports of idle instability and vacuum leaks in early production units. Later models also featured an updated ignition module to improve spark reliability under high-temperature conditions.
All A5.000-equipped Fiat 138 models comply with ECE Regulation 15 Phase II (VCA UK Type Approval #VCA/ECE/15/IT/856).
The Fiat A5.000 is a 1,498 cc inline-four SOHC petrol engine designed for compact sedans (1980–1984). It combines carburettor-based fuel delivery with an aluminium cylinder head and belt-driven camshaft to deliver improved efficiency and reduced weight. Designed to meet ECE R15 Phase II standards, it balances economy with serviceability for everyday motoring.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,498 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 76.0 mm × 82.0 mm | |
| Power output | 59–64 kW (80–87 PS) | |
| Torque | 118–122 Nm @ 3,000 rpm | |
| Fuel system | Single/dual carburettor (Weber 32/34 IDF or 34 DMTR) | |
| Emissions standard | ECE R15 Phase II | |
| Compression ratio | 9.2:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Belt-driven camshaft | |
| Oil type | SAE 10W-40 mineral (API SE/CC) | |
| Dry weight | 122 kg |
The SOHC design provides linear power delivery ideal for city driving but requires strict adherence to 12,000 km service intervals to maintain timing belt integrity. SAE 10W-40 mineral oil is recommended due to compatibility with older seals and flat-tappet cam design. Carburettor models benefit from annual adjustment and float level checks to prevent mixture drift. The aluminium head reduces weight but requires precise torque sequencing during reassembly. From 1982, Fiat introduced improved EGR valve calibration and intake sealing (Fiat SIB 82-ME-01), reducing idle instability and vacuum leaks in later units.
Oil Specs: Requires SAE 10W-40 mineral oil meeting API SE/CC (Fiat SIB 82-ME-01). Modern synthetic oils not advised without seal compatibility check.
Emissions: All A5.000 models comply with ECE R15 Phase II (VCA Type Approval #VCA/ECE/15/IT/856). No Phase I variants were produced.
Power Ratings: Measured under ISO 1585 standards. 64 kW output applies to 138 S variant with 34 DMTR twin-choke carburettor and revised ignition timing (Fiat TIS Doc. M138-S-05).
Fiat Technical Information System (TIS): Docs M138-ENG-01, M138-S-05, SIB 82-ME-01
VCA Type Approval Database (VCA/ECE/15/IT/856)
ISO 1585:1996 Road vehicles — Engine test code — Net power
The Fiat A5.000 was used across Fiat's 138 series platforms with transverse mounting and no licensed external usage. This engine received platform-specific adaptations—twin-choke Weber 34 DMTR in 138 S trims—and from 1982, the facelifted 138 models adopted revised EGR calibration and improved intake sealing, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right side of the cylinder block near the starter motor (Fiat TIS M138-ENG-01). The 8th VIN digit indicates engine type ('A' for A5.000 series). Pre-1982 models have silver valve covers with ribbed design; post-1982 units use black-painted covers. Critical differentiation from older units: A5.000 has belt-driven camshaft and aluminium head, while pre-1980 engines use iron heads and chain drives. Service parts require model-year verification—EGR valves and intake manifolds differ pre- and post-1982 revisions (Fiat SIB 82-ME-01).
The A5.000's primary reliability risk is timing belt failure in high-mileage units, with elevated incidence in poorly maintained examples. Internal Fiat service reports from 1983 noted a significant share of pre-1982 engines requiring EGR valve replacement or carburettor overhaul beyond 80,000 km, while UK DVSA historic vehicle inspections cite mixture imbalance as a frequent cause of failed emissions tests. Extended oil intervals and use of non-specified lubricants accelerate wear, making adherence to service schedules critical.
Analysis derived from Fiat technical bulletins (1980-1984) and UK DVSA historic vehicle inspection data (2010-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FIAT 138-A5-000.
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