Carburettor (1.3 litre engine) - adjustments

Fuel and exhaust systems - carburettor models / Carburettor (1.3 litre engine) - adjustments

Note: Accurate adjustment of the carburettor is only possible if adjustment of the ignition timing, dwell angle and spark plug gaps is correct. Incorrect valve clearances can also effect carburettor adjustment Pierburg/Solex 2E3
Cut-off valve
1 To check the cut-off valve, apply battery voltage. It must be heard to click when the voltage is applied.

Choke valve gap
2 To check the choke valve gap the choke cover must be removed. Move the throttle valve and the fast idle cam so that the adjustment screw is against the highest cam stop. Now push the choke valve operating rod fully towards the adjustment screw (and pull-down unit), then check the choke valve-to-barrel clearance using a twist drill as a gauge. If necessary turn the adjuster screw as required to provide the specified choke valve gap (see illustrations).

16.2a Fast idle cam (1) and choke valve gap adjusting screw (2)

16.2b Checking choke valve gap

1 Choke valve operating rod (push in direction of arrow) 2 Twist drill

Accelerator pump injection capacity 3 The accelerator pump injection capacity can be checked in the same manner as that described for the Pierburg 2E3 carburettor but allow 1 second per stroke and 3 seconds between strokes (see illustration).

16.3 Accelerator pump adjustment

1 Fast idle cam clamp screw 2 Fast idle cam
A Increase capacity
B Decrease capacity

Choke
4 The automatic choke cover and choke housing alignment marks should correspond.

To check the choke, connect up a test lamp between a battery positive terminal and the choke lead. The test lamp should illuminate. If not, then the choke unit is defective and must be renewed.

5 The choke pulldown unit can be checked when removed but as this requires the use of a vacuum pump and gauge, it is a check best entrusted to your VW dealer. The pulldown unit can also be tested when the carburettor is in position in the vehicle. The air cleaner unit must be removed. Run the engine at idle speed then close the choke valve by hand and check that a resistance is felt over the final 3.0 mm of travel. If no resistance is felt, there may be a leak in the vacuum connections, or the pulldown unit diaphragm is broken, in which case the unit must be renewed.

Throttle valve
6 The basic Stage ll throttle valve adjustment is made during manufacture and should not require further adjustment. If, for any reason, the limiting screw has been removed or its setting altered, readjust it as follows.

7 Open the throttle valve and hold it in position by inserting a wooden rod or similar implement between the valve and venturi (see illustration). Using a rubber band, pretension the Stage ll throttle valve locking lever then unscrew the limiting screw to provide a clearance between the stop and the limiting screw. Now turn the limiting screw in so that it is just in contact with the stop. The limiting screw stop point can be assessed by inserting a thin piece of paper between the stop and screw. When the paper starts to get pinched between the two, the stop point is reached and from this point, tighten the limiting screw a further quarter turn then secure it with locking compound. Close both throttle valves then measure the locking lever clearances (see illustration). If the clearances are not as specified, then bend the levers as necessary.

16.7a Throttle valve basic setting showing rod to hold valve open (arrowed), lock lever (1) limiting screw (2) and stop (3)

16.7b Locking lever clearance with throttle valves closed

Clearance to equal 0.25 to 0.55 mm (each side)

Slow running and fast idle 8 To check and adjust the slow running setting, refer to Section 15, paragraphs 7 to 13 inclusive (see illustration).

16.8 Idle speed adjustment screw and guide sleeve (A) mixture screw (B)

9 To check and adjust the fast idle adjustment, first check that the engine is still at normal operating temperature. The air cleaner must be removed and the other provisional conditions must apply as for the slow running adjustment. Plug the air cleaner temperature control hose.

10 Restart the engine and open the throttle to give an engine speed of approx. 2500 rpm.

Press down the fast idle cam to its stop then move the throttle valve back so that the adjuster screw is on the second highest stop on the fast idle cam. In this position, the fast idle speed should be as specified. If the setting is incorrect, turn the adjustment screw in the required direction until it is correct (see illustration). Note that the screw may have a tamperproof cap fitted.

16.10 Fast idle speed adjustment screw (2)

11 On completion, unplug the temperature control connector and refit the air cleaner.