Checking and adjusting the Keihin carburetor (Audi 100 C3)

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 float for leaks, check the operation of the needle valve, replace faulty parts.

Adjusting the opening of the throttle valve of the 1st chamber when the cold engine is idling

To adjust without removing the carburetor from the engine, warm up the engine to operating temperature.

Remove the air filter.

Disconnect the vacuum supply hose from the 1st chamber throttle actuator.

Attach a reference tachometer.

Start a cold engine and let it idle.

Check the crankshaft speed using the tachometer, which should be 3500 rpm.

If necessary, adjust the idle speed of the cold engine crankshaft by moving the fork-type lever of the 1st chamber throttle valve drive.

Remove the carburetor and check the opening of the throttle valve of the 1st chamber, which on cars with a manual transmission should be within 1.3-0.1 mm, on cars with an automatic transmission - 1.5±0.1 mm.

If there is a deviation from the norm, achieve the proper opening of the throttle valve of the 1st chamber by acting on the fork lever of its drive.

Adjusting the throttle valve starting clearance

Remove the carburetor and disconnect the pneumatic drive rod from the throttle valve of the 1st chamber.

Insert a 9.5mm diameter drill bit between the carburetor body and the automatic starting device actuated throttle control lever.

If necessary, achieve the proper clearance by changing the length of the automatic starting device drive rod.

Measure the throttle valve starting clearance using a set of feeler gauges, which should be 0.6±0.07 mm on vehicles with a manual transmission and 0.7±0.07 mm on vehicles with an automatic transmission.

If there is a deviation from the norm, set the required starting clearance by changing the position of the throttle control lever thrust roller.

Adjusting the starting clearance of the air damper

Remove the air filter.

Remove the automatic starting device cover.

Set the air damper control lever to the stop position by turning it counterclockwise and lock it in this position.



Set the air damper pneumatic actuator rod to the stop position.

Using a set of feeler gauges, measure the starting clearance of the air damper, which should be 5.6±0.15 mm.

If necessary, adjust the air damper starting clearance by bending the stop lever.

Adjusting the opening of the throttle valve of the 2nd chamber

Remove the carburetor.

Loosen the 2nd chamber throttle valve limit screw until it is clear of the bracket. Tighten the limit screw until it touches the bracket, then tighten it another 1/2 turn.

Lock the 2nd chamber throttle valve limit screw with a drop of paint.

After installing the carburetor, adjust the engine idle speed.

Adjusting the performance of the accelerator pump

Remove the carburetor and place a measuring cup with a funnel underneath it.

Move the automatic starting device control lever towards the opening direction.

Move the throttle control lever of the 1st chamber away from the rod and pneumatic drive.

Install a 12 mm diameter rod between the carburetor body and the 1st chamber throttle control lever, driven by an automatic starting device.



Smoothly open and close the throttle valve of the 1st chamber completely, thereby activating the accelerator pump.

Measure the amount of fuel that has flowed into the measuring cup and compare it with the standard (see subsection "Detailed technical specifications").

If there is a deviation from the norm, adjust the required performance of the accelerator pump by changing the stroke of the accelerator pump drive lever, slightly bending the stop lever.

Adjusting the idle speed of a warm engine

Before adjusting the idle speed, check that the ignition timing is set correctly and turn off all electrical consumers.

Warm up the engine to operating temperature.

Attach a reference tachometer.

Adjust the engine idle speed by turning the stop screw of the 1st chamber throttle control lever, which rests on the 1st chamber throttle pneumatic drive lever.

Connect the gas analyzer according to the operating instructions.

Remove the air cleaner cover and disconnect the crankcase ventilation hose.

Check and, if necessary, adjust the CO content using the idle mixture quality (composition) screw.





Check and, if necessary, readjust the engine idle speed.