Checking and adjusting the Pierburg 1B3 carburetor (VW Passat B2)

Checking the fuel level in the float chamber

The position of the float in the float chamber is not adjustable. If a malfunction is detected, check the tightness of the float and the technical condition of the needle valve, replace the faulty parts.

Adjusting the idle speed of a cold engine

Warm up the engine.

Connect the tachometer.

Stop the engine.

Open the throttle valve fully, placing the profiled throttle opening cam in the appropriate position.

Start the engine without pressing the accelerator pedal.

Check the engine crankshaft speed, which should be within 3500-3900 rpm.

If necessary, adjust the crankshaft speed using the throttle stop screw, which rests on the profiled throttle opening cam.

Adjusting the starting clearances of the air damper

Remove the starter cover.

Open the throttle valve fully, placing the throttle valve opening cam on the appropriate profile.

Connect a vacuum gauge and a vacuum pump to the air damper pneumatic drive and create a vacuum of 100 mbar in the pneumatic drive.

If the air damper pneumatic drive is hermetically sealed, the vacuum should not decrease by more than 5 mbar per minute and should not decrease to less than 40 mbar.

Bring the vacuum in the air damper pneumatic drive to 200-300 mbar.

Measure the starting gap of the first stage of the air damper using a set of feeler gauges, which for cars with a manual transmission should be 2.0±0.15 mm, for cars with an automatic transmission - 2.4±0.15 mm.

If necessary, set the required gap using the pneumatic drive diaphragm stroke adjustment screw located on its cover (see photo).

Close the atmospheric hole of the air damper pneumatic drive with a plug, create a vacuum of 200 mbar in the pneumatic drive, which, if the pneumatic drive is sealed, should remain unchanged for at least 1 min.

Measure the starting gap of the second stage of the air damper using a set of feeler gauges, which on vehicles with a YN engine should be within 4.3±0.15 mm, on vehicles with a WV engine with a manual transmission - 3.5±0.15 mm, with an automatic transmission - 3.3+0.15 mm.

If necessary, set the proper clearance using the adjusting screw on the end of the air damper pneumatic actuator rod.

Adjusting the throttle opening

The throttle position is adjusted at the factory, but if the adjustment is out of adjustment, it can be restored as follows:

• remove the throttle limit screw plug;
• connect the vacuum gauge in parallel to the vacuum regulator of the ignition timing sensor-distributor;
• start and warm up the engine;
• move the throttle control sector away from the idle stop;
• turn the throttle valve limit screw so that the vacuum begins to increase;
• turn the throttle valve limit screw until a minimum vacuum is obtained, then turn it back another half turn;
• adjust the idle speed of a warm engine as indicated below;
• install a new plug on the throttle valve limit screw.

Adjusting the accelerator pump

Remove the carburetor.

Fill the carburetor float chamber with fuel and place a measuring cup with a funnel under the carburetor.

Move the throttle control sector away from the idle stop.

Slowly move the throttle valve ten times from stop to stop, spending approximately 3 seconds each time, thereby activating the accelerator pump.

Measure the amount of fuel in the measuring cup: in one cycle the accelerator pump should supply 0.9+0.15 cm³ of fuel.

If necessary, adjust the performance of the accelerator pump by moving the cam of the accelerator pump drive lever on the bracket, after first loosening the lock screw.

Adjusting the idle speed of a warm engine

Adjustment of the engine idle speed must be performed on a warmed-up engine with adjusted clearances in the valve drive mechanism, with the ignition timing set correctly.

Connect the tachometer and gas analyzer in accordance with the operating instructions.

Use the mixture quantity adjusting screw to set the crankshaft speed within 900-1000 rpm.

Using the mixture quality (composition) adjustment screw, achieve a carbon monoxide (CO) content in the exhaust gases of no more than 0.5-1.5%. Restore the crankshaft speed to 900-1000 rpm. If necessary, restore the specified CO content.