Maximum Charging Pressure
Checking the maximum charging pressureTools: Pressure gauge 83 93 514
Test wiring harness with service box 83 93 546 (up to and incl. 1985 models) or 83 94 074 (1986 models onwards)
1. Run the hose of the pressure gauge from the passenger compartment to the engine compartment. Position the pressure gauge vertically to avoid erroneous readings.
2. Connect the hose of the pressure gauge between the connection on the inlet manifold and the hose to the pressure switch.
3. a. Tilt the rear seat cushion forward and disconnect the control unit cables.
b. As from 1986 models:
Lift the catch and detach the wiring loom connector from the control unit, and lift up the control unit.
4. a. Connect the test wiring harness with the service box between the normal harness connector for the control unit and the control unit itself.
b. As from 1986 models:
Run the test loom with control box into the cabin.
5. a. Set the 'knock-detector' switch on the service box to the "Off" position.
(This is to prevent the knock detector from varying the charging pressure while readings are being taken.)
b. As from 1986 models:
Set the knock-detector switch on the control box to ON and the solenoid-valve switch to ON.
Note:
- Depending on the type of fuel in the tank, the engine may knock continually while readings are being taken.
- Checking the maximum charging pressure in a road test must be performed as quickly as possible (3-5 seconds approx.) to avoid abnormally high temperatures building up in the brake linings.
- The car should be driven at least 0.6 miles (1 km) between each test and after testing has been completed in order to allow the brake linings to cool.
- The engine should be at full operating temperature.
A. Manual transmission. The test should be started in 3rd gear with engine speed below 1,500 r/min.
B. Automatic transmission. The test should be started with the gear selector in "1" and engine speed below 1,500 r/min.
6. Depress the accelerator to the floor. When the engine speed approaches 3,000 r/min charging apply the brakes (while keeping the accelerator pressed to the floor) so that the engine is held under full load at 3,000 r/min.
Read the charging pressure off the pressure gauge. The gauge must be vertical in order to obtain a true reading.
Note: A charging pressure surge may be noted when the engine is accelerated to maximum, i.e. the charging pressure will momentarily exceed the pre-set maximum figure when the accelerator is floored.
7. Once stabilized the charging pressure reading should be the same as that specified.
If the charging pressure reading is within the tolerances specified, remove the testing equipment.
If the charging pressure reading is not within the tolerances specified, first check the basic setting on the road and then refer to the fault-diagnosis table.