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Fuel Pressure Regulator
The fuel pressure regulator is fitted to control the pressure of fuel delivered at the injectors by sensing variations in manifold depression; this is to ensure that the actual quantity of fuel released by the injectors is governed by one factor only - injector 'open time'.
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Part 1 INTRODUCTION and DESCRIPTION
Part 2 SYSTEM OPERATION
Part 3 ELECTRICAL FUNCTION and CCT OPERATION
Part 4 APPROACHING A TUNE UP and DIAGNOSIS
Part 5 ELECTRICAL TESTS and EQUIPMENT
Part 6 HINTS and TIPS
The pressure regulator is fitted in the excess fuel return pipe (E), close to the injector fuel rail with its fuel supply (F) as seen in Fig.2.2. It has two chambers separated by a diaphragm (R1); one chamber contains fuel from the supply line (F), the other is linked by a pipe to the engine side of the throttle butterfly to sense manifold depression.
In the rest position the spring (R2) holds the diaphragm valve against the fuel return pipe.
Under conditions of low manifold depression, e.g. full throttle (Fig.2.2A), the spring continues to hold the diaphragm on its fuel return pipe seat. In these circumstances, pump pressure must reach approximately 36 Ib/sq.in to move the diaphragm valve against spring pressure and allow excess fuel to return to the tank.
When manifold depression is high, e.g. idle and overrun (Fig.2.2B), the diaphragm valve is drawn against spring pressure. The fuel return is opened and the fuel pressure falls to 26 Ib/sq.in Any intermediate depression will regulate fuel pressure between the minimum and maximum.
In this way fuel pressure varies according to manifold depression and ensures the amount of fuel delivered by the injectors is governed only by the injector 'open time'.
When manifold depression is low (Fig.2.2A), fuel pressure needs to be high to ensure sufficient fuel is forced through the injector for a given injector 'open time', say 0.003 cc of fuel per 10 millisecond period.
When manifold depression is high (Fig.2.2B), the depression will try to 'suck' fuel from the injector nozzle. Therefore the fuel pressure needs to be reduced by the action of the regulator to ensure the same 0.003 cc of fuel will pass through the injector in the same 10 millisecond period.
The Rover SD1 Efi Operations, Test and Instruction Manual consists of 35 pages in addition to an attractive front cover printed double sided on good quality A4 paper enclosed in a plastic folder. The pages are ideal for laminating to provide protection in the workshop environment.