Checking And Adjusting Drive Belt Of Air Pump

Check ing

Drive belt tightness is correct if belt gives under thumb pressure applied at point midway between sprockets by 6 to 8 mm.


1. Loosen bolt slightly (arrow).

1. Loosen bolt slightly (arrow).

Porsche 930 Cold Air Intake

2. Turn self-locking adjusting bolt until belt tightness is correct. Tighten bolt.

Porsche 930 1977 Vacuum Line

1 - Air distributor a - Connection for brake booster

2 - Throttle housing

3 - Control pressure regulator

4 - Auxiliary air regulator

5 - Auxiliary air valve

6 - Ignition distributor

7 - Thermo time valve

8 - Pop-off valve

9 - Deceleration valve

10 - Intake air intercooler

11 - Air cleaner

12 - Waste gate

14 - Diverter valve

15 - Check valve

16 - EGR valve

Porsche 944 Vacuum Lines


Thermo time valve in vacuum line between distributor and throttle housing is closed on a cold engine.

This eliminates vacuum retard control and the ignition timing moves toward advance by approx. 15°, which provides a fast idle speed after a cold start.

After about 15 to 20 seconds the thermo time valve will open and let the vacuum take effect, which pulls back ignition timing toward retard to the specified value.

The thermo time valve has to be replaced, if there is no movement toward advance and the related fast idle speed after a cold start.

The thermo time valve operation can only be tested on a completely cold engine.


Porsche 930 Intake Schematic

Figure shows thermo time valve with intake air intercooler removed.

Thermo time valve can be replaced without removing intake intercooler.

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