dual empi 34 carburetors help
-
advinnie
- Posts: 974
- Joined: Mon Jun 10, 2013 4:54 am
dual empi 34 carburetors help
Hi all please help. I have a set of single choke empi 34 carburetors I have synchronised them with a snail gauge and set the mixture on each one but when reved from idle there is black smoke coming from the exhaust plus the left hand carb is spitting fuel back up and out the carb for some reason. Has anyone got any ideas whats happening cheers. Ps they are fitted to a 1600 twin port beetle the timing is set at 7.5 degrees BTDC at idle and 32 degrees BTDC max.
-
FJCamper
- Moderator
- Posts: 2910
- Joined: Wed Nov 14, 2007 2:19 pm
Re: dual empi 34 carburetors help
Hi Advinnie,
The black smoke is too rich an idle mixture. The fuel blowing back from one carb can also be idle, but usually, too lean!
With the engine off, air filters removed, look down the carb throats to see if both throttle plates are closed. If not adjust the linkage until they are. Have someone press down on the accellerator as you watch down the throat to see if both throttle plates are opening the same amount, and in fact giving you full throttle.
With the engine still off, turn in both idle mixture screws slowly until they stop. Then back each one out exactly one and one half turns.
Start the engine. Forget about your synchroniser. Run it by hand if you have to (controlling the throttle linkage) to get the engine warmed up, then adjust the idle screws (not the air/fuel mixture screws) until you can idle.
Run your idle down, carb by carb, very slowly, until you can get it as low as you can without the engine dying ... then slowly begin to turn one of the idle mixture screws inwards. Listen and feel for an increase or decrease in RPM. Do the same to the other carb.
This is where we get "balancing" the carbs. You need to find the spot where turning in or out on the screw causes that carb to idle badly, and readjust so it idles best.
Working from one carb to the next, get them balanced with each other.
Now rev it, and you should get no strong gas order, spitting, or popping on decelleration. If you do, something else is wrong out side the idle and air fuel adjustments, such as a vac leak.
If you do have the carbs balanced, you can gently fine tune them with your synchroniser.
FJC
The black smoke is too rich an idle mixture. The fuel blowing back from one carb can also be idle, but usually, too lean!
With the engine off, air filters removed, look down the carb throats to see if both throttle plates are closed. If not adjust the linkage until they are. Have someone press down on the accellerator as you watch down the throat to see if both throttle plates are opening the same amount, and in fact giving you full throttle.
With the engine still off, turn in both idle mixture screws slowly until they stop. Then back each one out exactly one and one half turns.
Start the engine. Forget about your synchroniser. Run it by hand if you have to (controlling the throttle linkage) to get the engine warmed up, then adjust the idle screws (not the air/fuel mixture screws) until you can idle.
Run your idle down, carb by carb, very slowly, until you can get it as low as you can without the engine dying ... then slowly begin to turn one of the idle mixture screws inwards. Listen and feel for an increase or decrease in RPM. Do the same to the other carb.
This is where we get "balancing" the carbs. You need to find the spot where turning in or out on the screw causes that carb to idle badly, and readjust so it idles best.
Working from one carb to the next, get them balanced with each other.
Now rev it, and you should get no strong gas order, spitting, or popping on decelleration. If you do, something else is wrong out side the idle and air fuel adjustments, such as a vac leak.
If you do have the carbs balanced, you can gently fine tune them with your synchroniser.
FJC
-
advinnie
- Posts: 974
- Joined: Mon Jun 10, 2013 4:54 am
Re: dual empi 34 carburetors help
Just to let you all know ive have found the problem the left carb was running very rich. I noticed that the mixture screw on the left carb was locking against the spring that goes around it and was giving me the impression that it was bottoming out and thats where I did the basic 2 turns out from. But once I sorted that out I got another 1 1/2 turns in on that mixture screw. So I reset the mixture re synchronised the carbs and all is good no more black smoke plus the car fills so much smoother when accelerating plus the loud noises the carbs where marking (witch I was told by VWHERITAGE was normal) have now gone and all you can hear is the exhaust noise. Thanks for your replys people cheers.