733 Stanadyne DS electronically controlled pump

This pump, introduced in 1993, is similar mechanically to the DB2 unit, but without the governor. It is capable of delivering 75 mm3 per stroke at 1200 bar at the injectors of four-cylinder engines. A high capacity belt drive can be employed if required.

The quantity of fuel delivered to the four plunger is regulated by an electronically controlled poppet type spill valve. A stepper motor actuates the cam-ring advance mechanism. With these arrangements, both the timing and quantity of fuel injected are accurately regulated in relation to load, speed and other engine parameters, while keeping to a minimum, under all conditions of operation, emissions of HC, CO, NO^ and smoke. Accuracy of control is further assured by housing the cam rollers and tappets in the large diameter drive shaft with zero backlash. Thus the distributor is isolated from the drive, and therefore isolated from torsional oscillations that might lead to inaccuracies in the timing.

The layout of the pump can be seen in Fig. 7.70. A commendable feature, and unique at the time of its introduction, is the housing of the spill valve coaxially in a counterbore in the end of the rotor. With this arrangement, the volume of fuel subjected to injection pressures is very small, so there is less risk of compressibility causing the injection characteristics to depart from those dictated by the profile of the cam geometry.

Situated at the top of the unit, the fuel inlet is readily accessible, even on V engines. Other advantages claimed by Stanadyne are as follows. A heavy duty drive, and flexibility in respect of the all of the following: governing, idle speed and cold running control, fuel metering and timing control on a shot-to-shot basis.

Fig. 7.71 illustrates the control system. Pump speed, angular pulse train data and data based on signals from the engine-mounted sensors are continuously updated by the electronic control module (ECM). They are processed by custom algorithms, and the resultant command signals are sent to the pump-mounted solenoid driver (PMD) and cam-ring advance stepper motor.

Because a single, high speed solenoid is used for the control functions, the benefits of ease, flexibility and accuracy of signal processing associated

Stanadyne Pump
Fig. 7.70 The Stanadyne DS electronically controlled pump was introduced late in 1993

OSTE | pump speed and jii reference

Crankshaft reference

Coolant temperature Intake air temperature a LL

Manifold pressure

Start of injection

Start of injection

Throttle sensor

Throttle sensor

Fuel

Lamp Temperature o r~

Processor network

Memory

Warning lamp

Switched inputs n

Outputs

Spare

Inject

Start aids

Communications f ? ?

Diagnostics a

Pump mounted | driver

Starting aids

DS pump

EGR control

Fig. 7.71 Schematic diagram of the DS electronic control system

Closure

with digital control have been obtained. Fuel metering and timing are regulated as a function of the input data to the ECM, which controls the PMD. The latter supplies the injection command signals and a constant current. Closure of the poppet type spill valve is detected by the PMD and signalled back to the ECM. The timing and quantity of fuel needed for each injection are updated on a shot-to-shot basis, so the engine response to changes in load is virtually instantaneous.

As the control strategy is angle, instead of time, based, the performance of the system is outstandingly good. This follows from the fact that the requirements for both metering and timing are functions of crankshaft angle. The outcome is good performance under transient conditions.

An encoder on the pump drive shaft serves as a high resolution clock. Its performance is enhanced by a phase lock loop (PLL) circuit in the ECM, which gives a resolution of 0.04°. Control over the metering and timing events is exercised, by a series of digital counters in the ECM, on the basis of signals received from the angular clock.

Lucas Epic Diagnostic

Fig 7.72

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  • Adelbert
    How to disassemble stanadyne injector pump diagram?
    8 months ago

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