Volvo Coupes/Sedans/Wagons 1970-1989 Repair Guide

General Information


Fuel injection combined with electronics and various engine sensors provides a precise fuel management system that meets all the demands for improved fuel economy, increased performance and lower tailpipe emissions. A fuel injected engine generally averages ten percent more power and fuel economy (with lower emissions) than a carbureted engine.

Because of its precise control, fuel injection allows the engine to operate at the optimum (stoichiometric) fuel ratio of 14.7:1 (14.7 parts air to 1 part fuel) throughout the entire range of engine operation-from idle through wide-open throttle. By using an oxygen sensor to measure the content of the exhaust gasses, the Electronic Control Unit (ECU), an on-board computer, can adjust the fuel mixture in response to the changing temperature, load and altitude conditions.

It is important to identify all system components, how they work and their relationship to one another before attempting any maintenance or repair on the system. All fuel injection systems are delicate and vulnerable to damage from dust, dirt, water and careless handling. The shock of hitting a cement floor when dropped from waist height can ruin a computer unit. Because of the close tolerances involved within a fuel injector, any particle of rust or dirt in the fuel lines can cause more damage than a well placed grenade.

Many components, while similar in appearance, can vary in their function or electrical properties. Each individual system has some sensors, capabilities and characteristics unique to its own design. Further, injection systems receive constant modifications and improvements during the production run. For these reasons, the careful recording of part numbers and/or engine numbers is essential to obtaining the correct replacement parts.