Peugeot 405 Manual

Carburettor - fault diagnosis, overhaul and adjustments
Fuel/exhaust systems - carburettor models / Carburettor - fault diagnosis, overhaul and adjustments


Fault diagnosis
1 If a carburettor fault is suspected, always check first that the ignition timing is correctly set, that the spark plugs are in good condition and correctly gapped, that the accelerator and choke cables are correctly adjusted, and that the air cleaner filter element is clean; refer to the relevant Sections of Chapter 1, Chapter 5 or this Chapter. If the engine is running very roughly, first check the valve clearances as described in Chapter 1, then check the compression pressures as described in Chapter 2.

2 If careful checking of all the above produces no improvement, the carburettor must be removed for cleaning and overhaul.

3 Prior to overhaul, check the availability of component parts before starting work; note that most sealing washers, screws and gaskets are available in kits, as are some of the major sub-assemblies. In most cases, it will be sufficient to dismantle the carburettor and to clean the jets and passages.

Overhaul
Note: Refer to the warning note in Section 1 before proceeding. Only carry out the procedures described in this Section, as special gauges are required for a more detailed overhaul. The following procedure applies to the Solex 34-34 Z1 carburettor.

4 Remove the carburettor from the vehicle as described in Section 12.

5 Unscrew the idle cut-off solenoid from the carburettor body, and remove it along with its plunger and spring. To test the solenoid, connect a 12-volt battery to it (positive terminal to the solenoid terminal, negative terminal to the solenoid body), and check that the plunger is retracted fully into the body.

Disconnect the battery, and check that the plunger is pushed out by spring pressure. If the valve does not perform as expected, and cleaning does not improve the situation, the solenoid valve must be renewed.

6 Remove the five screws and lift off the carburettor upper body.

7 Tap out the float pivot pin and remove the float assembly, needle valve, and float chamber gasket. Check that the needle valve anti-vibration ball is free in the valve end, then examine the needle valve tip and seat for wear or damage. Examine the float assembly and pivot pin for signs of wear and damage. The float assembly must be renewed if it appears to be leaking - shake the float to detect the presence of fuel inside.

8 Unscrew the fuel inlet union and inspect the fuel filter. Clean the filter housing of debris and dirt, and renew the filter if it is blocked.

9 Undo the four screws, detach the accelerator pump cover, and remove the pump diaphragm and spring, noting which way around they are fitted. Examine the diaphragm for signs of damage and deterioration, and renew if necessary.

Remove the choke pull-down diaphragm and part-load enrichment diaphragms, and examine them in the same way.

10 Unscrew the idle jet from the upper body.

11 Unscrew both the primary and secondary combined air correction jets and emulsion tubes.

12 Using a long thin screwdriver, unscrew the main jets from the bottom of the emulsion tube drillings. Invert the carburettor and catch the jets as they fall out of the drillings.

13 Remove the idle mixture adjustment screw tamperproof cap. Screw the screw in until it seats lightly, counting the exact number of turns required to do this, then unscrew it. On refitting, screw the screw in until it seats lightly, then back the screw off by the number of turns noted on removal, to return the screw to its original position.

14 Clean the jets, carburettor body assemblies, float chamber and internal drillings. An air line may be used to clear the internal passages once the carburettor is fully dismantled. Caution: If high pressure air is directed into drillings and passages where a diaphragm is fitted, the diaphragm is likely to be damaged.

15 Use a straight edge to check all carburettor body assembly mating surfaces for distortion.

16 To test the carburettor heating element, connect a multimeter, set to the resistance function, between the heater wiring terminal and the carburettor body. A resistance reading of approximately 0.25 to 0.5 ohms should be obtained. If an open-circuit is present, or an extremely high resistance reading is obtained, it is likely that the heating element is faulty. A heating element repair kit is available from your Peugeot dealer. To renew the element undo the screw and remove the retaining plate, then slide the element holder, pin, element and insulating plate, noting each component correct fitted location. Fit the new components, ensuring each one is correctly positioned, and securely tighten the retaining screws. Note: Ensure that the insulating plate is correctly positioned between the heating element and body so that there is no danger of the element shorting out on the carburettor body.

17 On reassembly renew any worn components and fit a complete set of new gaskets and seals. A jet kit and a gasket and seal kit are available from your Peugeot dealer.

18 Reassembly is a reversal of the dismantling procedure. Ensure that all jets are securely locked in position, but take great care not to overtighten them. Ensure that all mating surfaces are clean and dry, and that all body sections are correctly assembled with their fuel and air passages correctly aligned.

Prior to refitting the carburettor to the vehicle, set the float height, throttle valve fast idle and choke pull-down settings as described below.

Adjustments
Idle speed and mixture
19 Refer to Chapter 1.

Float height setting
(Solex carburettor)
20 Invert the carburettor body, so that the float is at the top and the needle valve is depressed. Measure the distance between the upper edge of the float and the sealing face of the upper body (with its gasket fitted).

This measurement should be as given in the Specifications at the start of this Chapter.

21 If necessary, the float height can be adjusted by carefully bending the small tang on the float arm which contacts the needle valve.

Throttle valve fast idle setting (Solex carburettor)
22 Invert the carburettor and pull the carburettor choke linkage to fully close the choke valve. The fast idle screw will butt against the fast idle cam and force the throttle valve open slightly.

23 Using the shank of a twist drill, measure the clearance between the edge of the throttle valve and bore, and compare this to the clearance given in the Specifications at the start of this Chapter. If necessary, adjust by turning the fast idle adjustment screw in the appropriate direction until the specified clearance is obtained (see illustration).

13.23 Throttle valve fast idle setting (Solex carburettor)
13.23 Throttle valve fast idle setting (Solex carburettor)

Adjust screw Y until clearance X is as given in the Specifications

Choke pull-down setting (Solex carburettor)
24 Pull the carburettor choke linkage to fully close the choke valve, and hold the linkage in this position.

25 Attach a hand-held vacuum pump to the choke pull-down diaphragm, and apply a vacuum to the diaphragm so that the diaphragm rod is pulled fully into the diaphragm body. In the absence of a vacuum pump, the rod can be pushed into the diaphragm with a small screwdriver.

26 With the rod fully retracted, use the shank of a twist drill to measure the clearance between the edge of the choke valve and bore, and compare this to the clearance given in the Specifications (see illustration).

13.26 Choke pull-down setting (using a screwdriver to retract the diaphragm
13.26 Choke pull-down setting (using a screwdriver to retract the diaphragm rod) (Solex carburettor)

Adjust until clearance X is as specified

If necessary, remove the plug from the diaphragm cover and adjust by turning the adjustment screw. Once the pull-down setting is correctly adjusted, refit the plug to the diaphragm cover and remove the vacuum pump (where used).

Float height setting
(Weber carburettor)
27 For float and level settings, remove the float chamber cover and hold it vertically.

28 With the gasket in position, use a steel rule or vernier calipers to check the height of the floats. Bend the float tongue and connecting bars if necessary.

Choke opening after starting (Weber carburettor)
29 Remove the air inlet from the top of the carburettor. Pull the choke control knob out fully to close the choke flap.

30 Disconnect the vacuum pipe from the anti-flood capsule.

31 Connect a hand vacuum pump (or a modified bicycle pump) to the capsule. Apply vacuum (400 mm Hg approx.) to the capsule.

The choke flap should open far enough to admit a drill shank or rod 5 mm in diameter.

32 Adjust if necessary by means of the screw on the anti-flood capsule.

33 Disconnect the vacuum pump, remake the original vacuum connection, and close the choke flap.

34 Having adjusted the anti-flood capsule, move the choke opening roller into the recess of the cam as shown (see illustration).

13.34 Checking the choke mechanical opening (Weber carburettor)
13.34 Checking the choke mechanical opening (Weber carburettor)

a Cam 3 Roller

35 Check that the choke flap opening just admits a drill shank or rod 8 mm in diameter.

36 Adjust by turning the nut shown (see illustration) after removing the carburettor.

13.36 Choke mechanical opening adjustment nut (4) (Weber carburettor)
13.36 Choke mechanical opening adjustment nut (4) (Weber carburettor)


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