Design And Function

Electronic accessory pump for cars with B4194T and B4204T engines and automatic transmissions

Design and Function




Turbocharged gasoline engined cars with automatic transmission may start moving without throttle opening.
Braking in such circumstances by result in a reduced vacuum in the power brake booster.
To avoid this, an electronic accessory pump (3) is connected to the power brake booster via a T valve (5).

The electronic accessory pump (3), the vacuum control valve (4) and the pump relay (2) are positioned on a bracket under the left front fender.

The pump relay (2) is connected to the system relay (1) for the engine management system (EMS 2000).
The electronic accessory pump (3) activates if the vacuum in the power brake booster exceeds ± 40 kPa when the engine is running.

Note! When the ignition is on (engine not started) and a vacuum is requested, the electronic accessory pump (3) is activated and runs. The pump only runs for a few seconds because of the system relay (1).

The measurement range of the vacuum control valve (4) is 35 - 45 kPa