Function of Modulating Pressure Control Vacuum For Diesels

Function of Modulating Pressure Control by Vacuum on Vehicles with Diesel Engine

The vacuum control valve attached to the side of the injection pump controls the vacuum for the modulating pressure control.

The vacuum control valve is operated by the adjusting lever shaft of the injection pump and controls a vacuum of approx. 0.4 bar at idling speed and a vacuum of 0 bar at full throttle

Vacuum Diagram Vehicles with Engine 601, 602, 603






1 Injection pump
2 Transmission
61a 0.7 mm restriction (blue)
62 Air admission filter
62a 0.5 mm restriction (orange)
65 Vacuum control valve
67 Vacuum pump
72 Damper
a Air admission line to passenger compartment
b Key-operated cutoff
c Residual ancillanes
d for (USA) California to vacuum amplifier (EGR)
(SW) California only

SW black
bi blue
br brown
vi purple
ws white

Vacuum Diagram Vehicles with Engine 615, 616, 617






1 Injection pump
2 Transmission
61 0.5 mm restriction (white)
61a 0.7 mm restriction (blue)
65 Vacuum control valve
67 Vacuum pump
72 Damper
140 Check valve
d Air admission line to passenger compartment
b Key operated cutoff
c Residual ancillaries

SW black
bi blue
br brown
vi purple
ws white

The vacuum control valve is divided by a diaphragm (8) into an upper and lower diaphragm chamber. The upper diaphragm chamber (6) is linked by connection (2) to the vacuum pump. The bottom diaphragm chamber (7) is connected to atmosphere through an air admission line. A connection between both diaphragm chambers can only be created by the plate valve, in the valve body (9) moving vertically.

When the engine is not running, the force of the compression spring (10) pushes the valve body (9) down. The plate valve (14) above the valve spring (5) closes and separates the connection between the two diaphragm chambers.

When the engine is running, vacuum flows from the vacuum pump to connection (2) into the upper diaphragm chamber (6) and also through connection (3) to the vacuum unit at the transmission.

Air is released from the upper diaphragm chamber and the control line and the valve body (9) is pushed up against the force of the compression spring (10). As soon as the plate valve (14) is resting against the end tube (11), the connection to the vacuum pump is interrupted. If the valve body (9) is raised further by the lever (13), the plate valve (14) lifts off from the valve body (9) and opens the connection to atmosphere. The vacuum is reduced and the force of the compression spring (10) presses the valve body (9) down again. This procedure is repeated constantly so that a controlled vacuum is produced in the upper diaphragm chamber and in the control line. When the accelerator is depressed1 the flat coil spring (12) acts via the lever (13) on the valve body (9) against the force of the compression spring (10), the controlled vacuum is reduced and is non-existent at full throttle. The level of the vacuum at idling speed is dependent on the force of the spring (10).






2 Suction line (center)
3 Control line (side)
5 Valve spring
6 Upper diaphragm chamber
7 Lower diaphragm chamber
8 Diaphragm
9 Valve body
10 Compression spring
11 Tube
12 Flat coil spring
13 Lever
14 Plate valve