Carburettor (1.05 litre engine) - adjustments

Fuel and exhaust systems - carburettor models / Carburettor (1.05 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 31 PIC7
Bypass air cut-off valve 1 To check the bypass air cut-off valve when removed, depress the pin approximately 3 to 4 mm then energise it with battery voltage. A click should be heard and the pin should move out.

Cut-off valve
2 To check the cut-off valve for the main jets (where fitted), apply battery voltage. It must be heard to click when the voltage is applied.

Choke valve gap
3 To adjust the choke valve gap, operate the choke lever fully then return it to the smooth running detent and hold it there. With the choke spindle lever against the cam, check that the clearance between the choke valve and barrel is as shown in Specifications. Use a twist drill to make the check and if necessary, adjust the clearance by turning the adjusting screw as required (see illustrations).

15.3a Checking choke valve gap with twist drill

15.3b Adjusting screw location for choke valve gap (A) and choke valve gap smooth running detent eccentric pin (B)

4 Although the choke valve gap smooth running detent position is preset during manufacture its setting can be checked and if necessary adjusted. Pull the choke out fully, then push it onto the smooth running detent.

Press the choke lever against the cam and check the choke valve gap with a twist drill, as in the previous paragraph. If the gap is not as specified, adjust by turning the eccentric pin on the choke spindle lever.

Accelerator pump injection capacity 5 The accelerator pump injection capacity may be checked with the carburettor fitted or removed. However, the air cleaner must be removed and the float chamber must be full.

6 Open the choke valve and retain it in the open position with a piece of wire, then push a length of close fitting plastic tube over the injection pipe. Operate the throttle until fuel emerges then place the tube in a measuring glass. Operate the throttle fully five times allowing at least three seconds per stroke.

Divide the final quantity by five to determine the amount per stroke and compare with the amount specified. If necessary, reposition the adjusting screw on the accelerator pump lever (see illustration). Note that fuel must be injected into the throttle valve gap. If necessary, bend the injection pipe.

15.6 Accelerator pump adjuster screw

Slow running and fast idle 7 Run the engine to normal operating temperature then stop it. Connect a tachometer and, if available, an exhaust gas analyser.

8 Check that all electrical accessories are switched off and note that slow running adjustments should not be made while the radiator cooling fan is running.

9 Disconnect the crankcase ventilation hose from the air cleaner body and plug the air cleaner outlet.

10 Start the engine and let it idle. Check that the engine speed and CO content are as specified. If not, turn the two screws located above the cut-off solenoid alternately as necessary (see illustration).

15.10 Idle speed (A) and mixture (B) adjusting screw locations

11 If an exhaust gas analyser is not immediately available, an approximate mixture setting can be made by turning the mixture screw to give the highest engine speed.

12 Reconnect the crankcase ventilation hose. If this results in an increase in the CO content, the engine oil is diluted with fuel and should be renewed. Alternatively, if an oil change is not due, a long fast drive will reduce the amount of fuel in the oil.

13 Stop the engine and remove the tachometer and exhaust gas analyser.

14 To adjust the fast idle speed, first check that the engine is still at normal operating temperature. Remove the air cleaner.

15 With the engine stopped, pull the choke control knob fully out then push it in to the smooth running detent.

16 Retain the choke valve in its open position using an elastic band.

17 Connect a tachometer then start the engine and check that the fast idle speed is as specified. If not, turn the adjustment screw on the side of the choke lever cam. Note that this screw may also have a tamperproof cap (see illustration).

15.17 Fast idle speed setting

A Choke valve held open with rubber band B Adjustment screw

18 Stop the engine, disconnect the tachometer and elastic band, then refit the air cleaner. Push the choke control knob fully in.

Pierburg/Solex 1B3
19 All adjustments are as described for the Pierburg 2E3 carburettor fitted to the 1.3 litre engine, with the following additions.

Enrichment tube
20 With the choke valve closed, the bottom of the enrichment tube should be 1.0 mm from the valve (see illustration).

15.20 Enrichment tube adjustment

a = 1.0 ± 0.3 mm

Idle speed and mixture 21 Before making any adjustment, ensure that the automatic choke is fully open, otherwise the throttle valve linkage may still be on the fast idle cam.

Idle speed boost valve
22 The idle speed adjustment screw (see illustration) incorporates a vacuum-operated valve which opens if the idle speed drops below 700 rpm, thereby causing an increase in the idle speed. The valve is itself controlled by a two-way valve and further control unit.

The control unit monitors the engine speed and activates the two-way valve which applies vacuum to the idle valve.

15.22 Idle speed adjustment screw location

23 To test the system, run the engine at idle speed, then slowly reduce the engine speed by manually closing the choke valve. At 700 rpm there should be vacuum at the hose in the idle valve.

Fast idle speed
24 With the engine at normal operating temperature and switched off, connect a tachometer and remove the air cleaner.

25 Fully open the throttle valve, then turn the fast idle cam and release the throttle valve so that the adjustment screw is positioned on the second highest part of the cam.

26 Without touching the accelerator pedal, start the engine and check that the fast idle speed is as specified. If not, turn the adjustment screw on the linkage as necessary.

If a tamperproof cap is fitted, renew it after making the adjustment (see illustration).

15.26 Mixture (CO content) adjustment screw location

Choke valve gap
27 With the engine cold, fully open the throttle valve, then turn the fast idle cam and release the throttle valve so that the adjustment screw is positioned on the highest part of the cam.

28 Press the choke operating rod as far as possible towards the pull-down unit.

29 Using the shank of a twist drill, check that the distance from the choke valve to the carburettor wall is as specified. If not, adjust the screw behind the automatic choke.

Accelerator pump capacity 30 Hold the carburettor over a funnel and measuring glass.

31 Turn the fast idle cam so that the adjusting screw is off the cam. Hold the cam in this position during the following procedure.

32 Fully open the throttle ten times, allowing at least three seconds per stroke. Divide the total quantity by ten and check that the resultant injection capacity is as specified. If not, loosen the camplate locking screw, turn the camplate as required and tighten the screw (see illustration).

15.32 Accelerator pump adjustment

1 Nut
3 Camplate
2 Camplate locking screw

33 If difficulty is experienced in making the adjustment, check the pump seal and make sure that the return check valve and injection tube are clear.

Idle cut-off solenoid
34 When the ignition is switched on, the solenoid should be heard to click, indicating that the idle circuit has been opened.

35 If the solenoid is removed for testing, the plunger must first be depressed by 3.0 to 4.0 mm before switching on the unit.

Weber 32 TLA
Float level
36 With the upper part of the carburettor inverted and held at an angle of approximately 45°, the measurement “a” (see illustration) should be as shown. The ball of the float needle should not be pressed in against the spring when making the measurement,

15.36 Float level checking diagram

a = 28 ± 1.0 mm b = 45° angle

Idle speed and mixture 37 The procedure for checking and adjusting the idle speed and CO content are basically the same as given for the Pierburg 31 PIC-7 carburettor. Refer to the accompanying illustrations for the location of adjustment screws and to the Specifications for settings.

(see illustrations).

15.37a Idle speed adjusting screw (A) - pre June 1985

15.37b Idle speed adjusting screw (A) - from July 1985

15.37c Mixture (CO content) adjusting screw (B)

Idle speed boost valve 38 The idle speed boost valve is identical to the unit on the Pierburg 1B3 carburettor.

Choke valve gap (pull-down) 39 Remove the choke cover.

40 Place the fast idle speed adjusting screw on the highest step of the cam (see illustration). The manufacturer’s original instruction was to press the pull rod in the direction of the arrow shown, then to check that the choke valve gap is 2.5 + 0.2 mm. As from April 1987 however, this instruction is revised and it is now necessary to use a vacuum pump to apply 300 mbar vacuum on the pull-down unit. The choke valve gap in this case must be 2.0 + 0.2 mm.

15.40 Choke valve gap adjustment

1 Fast idle adjustment screw 2 Cam
3 Pull rod

41 Adjustment is made on the screw at the end of the pull-down device. Ensure that the spring “2” (see illustration) is not compressed when making the check.

15.41 Checking choke valve gap (pull-down)

1 Twist drill
2 Spring
3 Adjusting screw

Idle cut-off valve
42 To check the cut-off valve, apply battery voltage. The valve must be heard to click when voltage is applied.

Fast idle speed
43 Before carrying out this check, ensure that the ignition timing and manual idling adjustments are correct. The engine should be at normal operating temperature.

44 Remove the air cleaner.

45 Plug the temperature regulator connection.

46 Connect the tachometer.

47 Remove the choke cover and set the fast idle speed adjusting screw on the second highest step on the cam (see illustration).

15.47 Adjusting fast idle speed

1 Fast idle adjusting screw 2 Cam
3 Rubber band

48 Tension the operating lever with a rubber band so that the choke valve is fully open.

49 Without touching the accelerator pedal, start the engine, which should run at the fast idle speed specified.

50 Adjust the screw as necessary.

Choke valve gap (wide open kick) 51 Remove the air cleaner.

52 Fully open the throttle and hold it in this position.

53 Press the lever (1) upwards (see illustration).

15.53 Checking choke valve gap (wide open kick)

1 Pressure applied upwards 2 Twist drill

54 Check the gap with a twist drill. The gap should be as specified. If necessary, adjust by bending the lever (see illustration).

15.54 Adjusting choke valve gap (wide open kick)

Bend lever as required

Accelerator pump capacity 55 This can be checked by following the procedure given for the Pierburg 2E3 carburettor, with the following differences.

56 Open the throttle valve quickly when operating the pump (ie. one second per stroke, with pauses of three seconds between strokes).

57 The amount of fuel injected can be altered, but only very slightly, as follows: (see illustration).

15.57 Accelerator pump adjustment

1 Cam
2 Camplate
3 Camplate locking nut

58 Take the accelerator cable cam off the throttle valve lever.

59 Secure the accelerator pump cam with an M4 screw.

60 Loosen the locknut on the camplate securing screw. Loosen the screw and turn the camplate with a screwdriver clockwise to decrease injected fuel and anti-clockwise to increase injected fuel. Tighten the screw and locknut and recheck the injection capacity.