Volkswagen Owners Club Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi.

I have recently acquired a vw beetle 1303 from 1976 with a 1.6 engine. The engine has got some mods:

weber 3236 dfav carburetor;
contacteless ignition distributor
to name the most relevant.

The carburetor fine tunning has been adjusted with the help of a wide band lambda probe and runs very well at all circumstances except the cold start and first 30 seconds warm up phase.

The engine has got to be reved for 4/ 5 seconds with the starter and the gas pedal has got to be depressed 2 times to start the engine.

Things ive noticed:

Lambda value is very poor at cold start and warmup
The automatic choke in the carb is working flawlessly
The exhaust gas divert ducting for the intake manifold warm-up is not blocked

Things ive checked recently:
adjusted idling speed according to specs, 800-900 rpm at normal engine temperature
spark advance at 5 degree atdc at around 850 rpm at normal engine temperature

The primary idling jet is a 55 and the secondary is a 60 and I live in a warm, dry climate at sea level.

Ive not got much experience with this engines. What hints would you guys have to try to fix this behaviour?

Thanks in advance.
 

·
Registered
67 Bug. 2275cc, 10.1:1, 48IDA,Eagle2242Cam,2300Lb clutch, 3.85 diff. Lowered,roll bar, 5pt, swaybars
Joined
·
200 Posts
Not really a VW specific problem, but rather a tune-up problem for an engine that has a carb. It is obviously too lean when cold. You need to start by adjusting the choke closed more, there is a setting in the manual for the carb as to how closed it is when cold, usually checked with a drill bit between the choke blade and the carb.

Since it runs well after warm up, the jets should be ok. Start with the choke adjustment. Remember, it should be almost closed at startup when cold. These have an electric choke so make sure the power to the choke is present and don't turn on the key and let it stay on without starting the car immediately.
 

·
Registered
67 Bug. 2275cc, 10.1:1, 48IDA,Eagle2242Cam,2300Lb clutch, 3.85 diff. Lowered,roll bar, 5pt, swaybars
Joined
·
200 Posts
The only other usual thing to look at is the adjustment of the idle speed when the chokes are closed. It should be behind the choke heater assembly. What this does is when the choke is closed (engine/carb cold) it opens the throttle a little more than the normal idle speed screw making the engine run a little faster. This combined with a richer mixture should allow the engine to idle on its own just after starting on a cold morning. As the choke opens and you subsequently move the throttle petal, this fast idle positioner will release and then the normal idle screw maintains the throttle position at idle.

If you look at an original VW carb (PICT xxx type), you will see a big stepped metal plate that holds the throttle open a lot when cold and as the choke heater opens the choke, the throttle screw will slip onto different steps, closing the throttle little by little, till the engine is warm. This is essentially what the cold idle adjustment does on the weber carb.

Look here for instructions and pictures for the fast idle adjustment. Look for the fast idle screw.
 
1 - 5 of 5 Posts
Top