Contents: Adjusting the opening of the… ↳ Adjusting the fast idle speed ↳ Idle speed adjustment ↳ Adjustment data for the Pierburg 85… ↳
Elements of the two-chamber carburetor Pierburg 85 HF
A - bimetallic spring housing, B - sealing ring, C - automatic starting device cover, D - starting throttle valve vacuum regulator, E - second chamber vacuum regulator, F - idle speed adjustment screw, G - accelerator pump, H - full load enrichment device valve, J - throttle valve opening mechanism dash-pot, K - carburetor body, L - fuel supply nipple, M - first chamber main fuel jet, N - second chamber main fuel jet, O - carburetor cover, P - idle jet
Measuring the opening of the air damper of the Pierburg carburetor
Adjusting the fast idle speed of the Pierburg carburetor
The arrow shows the fast idle adjustment bolt.
Adjusting the idle speed of the Pierburg carburetor
A – speed adjustment screw,
B – mixture composition adjustment screw
The 1.8 dm³ REB engine is equipped with a two-chamber Pierburg 85 HF 9510 AB carburetor with independent control of the throttle valves of both chambers, with an automatic starting device and an accelerator pump.
Adjusting the opening of the starting air damper
1. Hold the throttle valve partially open and turn the fast idle cam so that the fast idle speed adjustment bolt touches the maximum level of the stepped disc.
2. Using a feeler gauge or a 3 mm diameter drill, measure the width of the gap between the edge of the starting air damper and the wall of the carburetor chamber (see Fig. Measuring the opening of the air damper of the Pierburg carburetor).
3. If necessary, adjust the required gap size using the adjusting bolt (2 mm Allen key).
Adjusting the fast idle speed
1. Bring the engine to normal operating temperature.
2. Check and, if necessary, adjust the idle speed and CO content.
3. Turn off the engine.
4. Remove the air filter.
5. Start the engine and let it idle.
6. Check whether the alignment marks on the starter cover and on the carburetor body are located opposite each other.
7. Set the end of the fast idle speed adjustment bolt to the minimum level of the stepped disk by moving the throttle lever (in the direction of increasing opening), turn the stepped disk accordingly and release the throttle lever.
8. Check the fast idle speed.
9. If necessary, adjust it using the fast idle speed adjustment bolt (see Fig. Adjusting the fast idle speed of the Pierburg carburetor).
Idle speed adjustment
This adjustment is performed with the engine warmed up to normal operating temperature and the current consumers switched off.
1. Before adjustment, check the tightness of the vacuum lines.
2. Connect the tachometer, check and, if necessary, adjust the idle speed by turning the screw (see Fig. Adjusting the idle speed of the Pierburg carburetor).
3. Connect the exhaust gas analyzer.
4. Increase engine speed to 3000 rpm and hold it for about 30 seconds.
5. Release the accelerator pedal. The RPM should return to the previous level. The CO content will initially increase and should stabilize after 5–25 seconds.
6. After 30 seconds of setting the speed, determine the CO content.
7. If necessary, adjust the CO content in the exhaust gases using the idle mixture composition screw (B).
Adjustment data for the Pierburg 85 HF 9510 AB carburetor
| Diffuser diameter (1/2 chamber) | 23/26 mm |
| Main fuel jet (1/2 chamber) | 107,5/ 130 |
| Idle fuel jet | 45 |
| Air jet | 115 |
| Starting throttle valve deflection | 3 mm |
| Adjusting the bimetallic spring of the starting throttle valve | in accordance with the markings on the cover of the starting device |
| Fast idle speed (support bolt at minimum disc level) | 830±30 rpm |
| Idle speed | 800±20 rpm |
| CO content | 1,3 % |
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