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Thu May 18, 2017 8:38 pm

Hello everyone!

No matter how much I adjust the choke counter clock wise, it opens up 2 steps immediately after starting the engine. It seems like vacuum is opening it up? It wouldn't bug me so much, however this isn't giving the engine the proper idle speed when cold and when the choke is close to disengaging the engine stalls. If I want it to keep running I have to hold the throttle open for a while til the engine warms up then it doesn't stall.

Does anyone have any idea what keeps the choke open and how to fix that? Or is it supposed to open even if it is cold?

Thu May 18, 2017 8:47 pm

boom10ful wrote: Hello everyone!

No matter how much I adjust the choke counter clock wise, it opens up 2 steps immediately after starting the engine. It seems like vacuum is opening it up?

That's kinda how it's supposed to work. The choke vacuum breaker diaphragm and arm should work in tandem to reduce the choking effect under throttle, but then they should be free to release once the throttle is released. This is to give you choke at idle where needed, but allows the car to drive normally when asked on a cold engine, something we all should be doing anyway, according to VW.

Here's the mechanicsm:

Chances are, your diaphragm, (triangle gasket here, three screws visible on carb body from rear,) is working correctly, but something is binding up and preventing the choke mechanism from rotating back into its spring-loaded position to work the airflow and fast idle cam.

What carb and distributor combination are you using? And tell us a little about how you like to set the three or four screws for carb adjustment?

Robbie

Thu May 18, 2017 8:52 pm

asiab3 wrote: boom10ful wrote: Hello everyone!

No matter how much I adjust the choke counter clock wise, it opens up 2 steps immediately after starting the engine. It seems like vacuum is opening it up?

That's kinda how it's supposed to work. The choke vacuum breaker diaphragm and arm should work in tandem to reduce the choking effect under throttle, but then they should be free to release once the throttle is released. This is to give you choke at idle where needed, but allows the car to drive normally when asked on a cold engine, something we all should be doing anyway, according to VW.

Here's the mechanicsm:

Chances are, your diaphragm, (triangle gasket here, three screws visible on carb body from rear,) is working correctly, but something is binding up and preventing the choke mechanism from rotating back into its spring-loaded position to work the airflow and fast idle cam.

What carb and distributor combination are you using? And tell us a little about how you like to set the three or four screws for carb adjustment?

Robbie

The distributor is a Bosch SVDA distributor. I set the carburetor by listening to the motor revs, then set the final idle speed to 900-1000 RPM.

Thu May 18, 2017 9:04 pm

boom10ful wrote:
The distributor is a Bosch SVDA distributor. I set the carburetor by listening to the motor revs, then set the final idle speed to 900-1000 RPM.

Maybe I didn't ask clearly; what model carb are you running?

Please set your carb on a warm engine like this:

- Turn small brass screw (#2) out four full turns from wherever it is.
- Turn small brass screw in 1/4 turn at a time until idle drops 50 RPM.
- Turn small brass screw out 1/4 turn.
- Reset idle speed (#3) if necessary using the big brass screw.
- Turn fast idle screw (#1) out until it does not touch the cam base.
- Turn fast idle screw in until it just barely touches the cam base, then in another 1/4 turn.

Setting by ear is a cool party trick, and it's fine if you know the physics involved with how the bypass circuitry works. But your answer above tells me that you want a 100% result with a 47% effort. Volkswagens don't work well that way.

Robbie

Thu May 18, 2017 9:12 pm

asiab3 wrote: boom10ful wrote:
The distributor is a Bosch SVDA distributor. I set the carburetor by listening to the motor revs, then set the final idle speed to 900-1000 RPM.

Maybe I didn't ask clearly; what model carb are you running?

Please set your carb on a warm engine like this:

- Turn small brass screw (#2) out four full turns from wherever it is.
- Turn small brass screw in 1/4 turn at a time until idle drops 50 RPM.
- Turn small brass screw out 1/4 turn.
- Reset idle speed (#3) if necessary using the big brass screw.
- Turn fast idle screw (#1) out until it does not touch the cam base.
- Turn fast idle screw in until it just barely touches the cam base, then in another 1/4 turn.

Setting by ear is a cool party trick, and it's fine if you know the physics involved with how the bypass circuitry works. But your answer above tells me that you want a 100% result with a 47% effort. Volkswagens don't work well that way.

Robbie

The steps you provided are how I have adjusted the carburetor. I have have a tach/dwell that helps me set the idle speed. I am NOT trying to take any shortcuts or anything, not sure where you came up with that idea.

Thu May 18, 2017 9:27 pm

Maybe I still didn't ask clearly; what model carb are you running?

I just want to make sure that we're all on the same page here. I often write a lot of words, and people ignore half of them, use the other half, and get pissed at me for messing things up. If I ask a question, it is because I need information that only exists in your physical car. Since I am not there, and my crystal ball is still at the powdercoat shop, I can not guess everything. (People who don't ask questions to diagnose cars need to go back and think about the first rule of Dunning-Kruger club.)

Do you have a vacuum gauge or a strobe timing light?

Thu May 18, 2017 9:30 pm

asiab3 wrote: Maybe I still didn't ask clearly; what model carb are you running?

I just want to make sure that we're all on the same page here. I often write a lot of words, and people ignore half of them, use the other half, and get pissed at me for messing things up. If I ask a question, it is because I need information that only exists in your physical car. Since I am not there, and my crystal ball is still at the powdercoat shop, I can not guess everything. (People who don't ask questions to diagnose cars need to go back and think about the first rule of Dunning-Kruger club.)

Do you have a vacuum gauge or a strobe timing light?

I am running a Solex 34 Pict 3 Carb. I have both a good quality Sears vacuum gauge and timing light; both made in the USA. :)

Thu May 18, 2017 9:49 pm

Excellent, thanks!

The cool thing about doing this professionally, is that I see hundreds of these cars a year. And I've started to notice trends, where certain stacks-up of parts just don't play out like they should according to the factory documentation. We also have a cool thread going here, since nobody else has jumped in. Not to bash on anybody, but a really good and thorough diagnostic session has a beginning, middle, and end (hopefully you get that far!) but sometimes too many people jumping into a thread destroy any semblance of diagnostic flow.

FIRST AND ALWAYS: "warming up" the car does not mean letting it idle until the choke is off. A "warm" engine means the oil has warmed up enough to allow it into the cooler, and the heads have warmed up enough to fully open a thermostat, if there is one. Ten minutes on the freeway is usually sufficient, but it may take exponentially longer if you're in a crowded city. (If there is no thermostat, you'll need to double your drive time.) Most choke-related issues are solved by following Volkswagen's instructions for cold starts:

the dudes who designed your engine on pencil and paper wrote: Do not try to warm the engine up by letting it idle with the vehicle stationary - drive off immediately.

If you're ready to get our heads out of Bentley Bible Land and start flying closer and closer to the sun, you're welcome to try out what I would do next. If you're worried about messing something up, or don't understand the whys of what we're doing, feel free to ignore ALL of the list, or ask questions before proceeding. Like I said above, there is no half-assing my writing. Whole-ass them, please.

1)
With a vacuum gauge connected to the vacuum advance port instead of the distributor, note the idle vacuum level on a fully warmed-up engine. (See above.) It should be zero. If not, please reply before continuing.

2)
With a strobe timing light connected, and your vacuum advance plugged back in, note the idle timing and RPM. Disconnect the vacuum hose. Does the idle speed drop? If so, reply here before continuing.

3)
Reattach the vacuum gauge, and turn the fast idle screw (#1) in 1/8 turn at a time until you see movement on the vacuum gauge. Turn the screw back out 1/8 turn. (We're ensuring the fast idle screw is as far in as possible without activating the vacuum advance. Vacuum advance occurs as soon as the throttle plate starts to open, destroying the idle bypass circuit flow.)

4)
Reattach vacuum advance hose, and note idle timing. It should be the same as before. If timing has increased, please reply accordingly.

--

Is there anything in the procedure above that stands out to you for a question, comment, or concern? And do you understand how we're trying to squeeze every bit of fast idle out of the car that we can without disturbing the actual idle circuit?

I should also caveat, that EVERY bit of this thread assumes that your valves are adjusted correctly, your dwell angle is 45° +/- 3°, and your timing is 28°-30° btdc with the hose off at maximum advance.

Good luck,
Robbie

Fri May 19, 2017 12:33 am

boom10ful wrote: It wouldn't bug me so much, however this isn't giving the engine the proper idle speed when cold and when the choke is close to disengaging the engine stalls. If I want it to keep running I have to hold the throttle open for a while til the engine warms up then it doesn't stall.
This sounds to me like you haven't adjusted the choke properly.
There is no proper fast idle rpm speed. You want to adjust the choke so it stays closed at idle long enough to keep the engine idling when you come to a stop. Since you engine idles fine when warmed up you are trying to keep the choke operating until this point in time. The fast idle speed will start high and as the choke butterfly opens it will drop step by step. It actually requires you to open the throttle to move down a step which is why driving while the choke is on is expected.

Also, choke time is NOT related to how warm/hot the engine is (not really). The temp of the choke coil element is what controls how OPEN the choke is. The warmer the coil is the more open the choke butterfly is. The choke heating element is powered by the black wire coming from the ignition #15 (+) terminal.

If for example, the choke opens fully after 5min from a cold morning start and your engine is still not yet warmed up, you need to rotate the choke coil body to force it to close more. This will require that the choke coil to heat up and expand more to get the choke fully open. This will take more time giving you additional minutes before the choke turns OFF.

There are markings on the choke coil and the body of the carb. If they are very far apart it usually means the choke is old/worn. It eventually gets to the point where the range of motion of the coil is no longer avaiable and you need to replace the choke coil. My original choke coil could NOT be adjusted to operate normally. Either it would open too soon, or it would never open all the way due to limited range of motion. The markings on the choke were about 1cm from where they should have been indicating the coil had weakened.. The replacement coil fixed it right up.

One last note: because the choke coil contracts based on the outside air temp you will need to adjust the choke at least twice a year in most locations because of the seasonal temp changes (spring and fall). If the temp changes are drastic, you may need more frequent adjustments.

Fri May 19, 2017 12:56 am

ashman40 wrote: boom10ful wrote: It wouldn't bug me so much, however this isn't giving the engine the proper idle speed when cold and when the choke is close to disengaging the engine stalls. If I want it to keep running I have to hold the throttle open for a while til the engine warms up then it doesn't stall.
This sounds to me like you haven't adjusted the choke properly.
There is no proper fast idle rpm speed. You want to adjust the choke so it stays closed at idle long enough to keep the engine idling when you come to a stop. Since you engine idles fine when warmed up you are trying to keep the choke operating until this point in time. The fast idle speed will start high and as the choke butterfly opens it will drop step by step. It actually requires you to open the throttle to move down a step which is why driving while the choke is on is expected.

Also, choke time is NOT related to how warm/hot the engine is (not really). The temp of the choke coil element is what controls how OPEN the choke is. The warmer the coil is the more open the choke butterfly is. The choke heating element is powered by the black wire coming from the ignition #15 (+) terminal.

If for example, the choke opens fully after 5min from a cold morning start and your engine is still not yet warmed up, you need to rotate the choke coil body to force it to close more. This will require that the choke coil to heat up and expand more to get the choke fully open. This will take more time giving you additional minutes before the choke turns OFF.

There are markings on the choke coil and the body of the carb. If they are very far apart it usually means the choke is old/worn. It eventually gets to the point where the range of motion of the coil is no longer avaiable and you need to replace the choke coil. My original choke coil could NOT be adjusted to operate normally. Either it would open too soon, or it would never open all the way due to limited range of motion. The markings on the choke were about 1cm from where they should have been indicating the coil had weakened.. The replacement coil fixed it right up.

One last note: because the choke coil contracts based on the outside air temp you will need to adjust the choke at least twice a year in most locations because of the seasonal temp changes (spring and fall). If the temp changes are drastic, you may need more frequent adjustments.

I've tried 2 different chokes but the results are the same. I adjust them so that there is a sliver of a gap left in the carb and that the step on the side is on its highest position. However, when I turn on the car, it immediately goes from the highest step, to the third step. It runs fine, but when it reaches the third or final step then the car loses idle speed and stalls.

Thu May 25, 2017 12:38 pm

asiab3 wrote: Excellent, thanks!

The cool thing about doing this professionally, is that I see hundreds of these cars a year. And I've started to notice trends, where certain stacks-up of parts just don't play out like they should according to the factory documentation. We also have a cool thread going here, since nobody else has jumped in. Not to bash on anybody, but a really good and thorough diagnostic session has a beginning, middle, and end (hopefully you get that far!) but sometimes too many people jumping into a thread destroy any semblance of diagnostic flow.

FIRST AND ALWAYS: "warming up" the car does not mean letting it idle until the choke is off. A "warm" engine means the oil has warmed up enough to allow it into the cooler, and the heads have warmed up enough to fully open a thermostat, if there is one. Ten minutes on the freeway is usually sufficient, but it may take exponentially longer if you're in a crowded city. (If there is no thermostat, you'll need to double your drive time.) Most choke-related issues are solved by following Volkswagen's instructions for cold starts:

the dudes who designed your engine on pencil and paper wrote: Do not try to warm the engine up by letting it idle with the vehicle stationary - drive off immediately.

If you're ready to get our heads out of Bentley Bible Land and start flying closer and closer to the sun, you're welcome to try out what I would do next. If you're worried about messing something up, or don't understand the whys of what we're doing, feel free to ignore ALL of the list, or ask questions before proceeding. Like I said above, there is no half-assing my writing. Whole-ass them, please.

1)
With a vacuum gauge connected to the vacuum advance port instead of the distributor, note the idle vacuum level on a fully warmed-up engine. (See above.) It should be zero. If not, please reply before continuing.

2)
With a strobe timing light connected, and your vacuum advance plugged back in, note the idle timing and RPM. Disconnect the vacuum hose. Does the idle speed drop? If so, reply here before continuing.

3)
Reattach the vacuum gauge, and turn the fast idle screw (#1) in 1/8 turn at a time until you see movement on the vacuum gauge. Turn the screw back out 1/8 turn. (We're ensuring the fast idle screw is as far in as possible without activating the vacuum advance. Vacuum advance occurs as soon as the throttle plate starts to open, destroying the idle bypass circuit flow.)

4)
Reattach vacuum advance hose, and note idle timing. It should be the same as before. If timing has increased, please reply accordingly.

--

Is there anything in the procedure above that stands out to you for a question, comment, or concern? And do you understand how we're trying to squeeze every bit of fast idle out of the car that we can without disturbing the actual idle circuit?

I should also caveat, that EVERY bit of this thread assumes that your valves are adjusted correctly, your dwell angle is 45° +/- 3°, and your timing is 28°-30° btdc with the hose off at maximum advance.

Good luck,
Robbie

Alright so I finally had a chance to do this procedure. Valves have been adjusted 100 miles ago. Timing was at 4 degrees BTC at idle the whole time. Dwell is at 46 degrees. Vacuum was 0 at idle.

However, I could NOT get the vacuum to increase by adjusting the fast idle screw even to 1600 RPM. Vacuum was still 0.

Thu May 25, 2017 1:16 pm

boom10ful wrote: Alright so I finally had a chance to do this procedure. Valves have been adjusted 100 miles ago. Timing was at 4 degrees BTC at idle the whole time. Dwell is at 46 degrees. Vacuum was 0 at idle.

However, I could NOT get the vacuum to increase by adjusting the fast idle screw even to 1600 RPM. Vacuum was still 0.

Great, thanks for getting back! What is your timing at maximum advance, with the hose off? That's what we care about more, since we don't load up the engine at idle really.

Robbie

Thu May 25, 2017 2:30 pm

boom10ful wrote: asiab3 wrote: 3)
Reattach the vacuum gauge, and turn the fast idle screw (#1) in 1/8 turn at a time until you see movement on the vacuum gauge.

Timing was at 4 degrees BTC at idle the whole time. Dwell is at 46 degrees. Vacuum was 0 at idle.

However, I could NOT get the vacuum to increase by adjusting the fast idle screw even to 1600 RPM. Vacuum was still 0.
This doesn't sound correct. :? :(

With your vacuum gauge connected to the left side vacuum advance port on the carb, there should be no vacuum at warmed up idle. But as soon as the throttle is cracked opened, the ported vacuum port which sits just above the closed throttle should be exposed to intake vacuum. The vacuum reading on the left side vacuume advance port of the carb should jump into the 10-15in-Hg range. You are saying that using the throttle arm screw to open the throttle and raise the idle rpms DOES NOT increase the vacuum???!!! This sounds like your ported vacuum port is plugged?!

Remove the carb and spray come carb cleaner into the vacuum advance port of the carb. You should see liquid carb cleaner spraying out a small hole in the carb throat just above the closes throttle plate. If you don't see a stream of fluid your port is plugged. You should soak your carb overnight in carb cleaner to dissolve any deposits in the passages and then use compressed air from a compressor to blow the passages clear from the carb throat end of the passage.

Thu May 25, 2017 2:33 pm

ashman40 wrote: boom10ful wrote: asiab3 wrote: 3)
Reattach the vacuum gauge, and turn the fast idle screw (#1) in 1/8 turn at a time until you see movement on the vacuum gauge.

Timing was at 4 degrees BTC at idle the whole time. Dwell is at 46 degrees. Vacuum was 0 at idle.

However, I could NOT get the vacuum to increase by adjusting the fast idle screw even to 1600 RPM. Vacuum was still 0.
This doesn't sound correct. :? :(

With your vacuum gauge connected to the left side vacuum advance port on the carb, there should be no vacuum at warmed up idle. But as soon as the throttle is cracked opened, the ported vacuum port which sits just above the closed throttle should be exposed to intake vacuum. The vacuum reading on the left side vacuume advance port of the carb should jump into the 10-15in-Hg range. You are saying that using the throttle arm screw to open the throttle and raise the idle rpms DOES NOT increase the vacuum???!!! This sounds like your ported vacuum port is plugged?!

Remove the carb and spray come carb cleaner into the vacuum advance port of the carb. You should see liquid carb cleaner spraying out a small hole in the carb throat just above the closes throttle plate. If you don't see a stream of fluid your port is plugged. You should soak your carb overnight in carb cleaner to dissolve any deposits in the passages and then use compressed air from a compressor to blow the passages clear from the carb throat end of the passage.

Sigh, that's what I get by not reading directions! :oops:. Thanks! I was adjusting the big bypass screw, NOT the top screw. I'll need to warm it up good again to do this. I'll come back and update.

Thu May 25, 2017 2:52 pm

asiab3 wrote: boom10ful wrote: Alright so I finally had a chance to do this procedure. Valves have been adjusted 100 miles ago. Timing was at 4 degrees BTC at idle the whole time. Dwell is at 46 degrees. Vacuum was 0 at idle.

However, I could NOT get the vacuum to increase by adjusting the fast idle screw even to 1600 RPM. Vacuum was still 0.

Great, thanks for getting back! What is your timing at maximum advance, with the hose off? That's what we care about more, since we don't load up the engine at idle really.

Robbie

Timing is a bit jumpy but its in between 28-30 degrees btdc.

Thu May 25, 2017 3:25 pm

Alright it's all adjusted now.

Thu May 25, 2017 5:42 pm

boom10ful wrote: Alright it's all adjusted now.

And you've run the procedure?

Thu May 25, 2017 5:53 pm

asiab3 wrote: boom10ful wrote: Alright it's all adjusted now.

And you've run the procedure?

Yes, however I've almost about had it with this dam car :x. I've noticed that when I have it at a steady throttle that the RPMs will noticeably drop a bit. Is that normal? This happens when its parked and I'm manually giving it gas at the back.

It also still refuses to idle when the choke is off until it is driven a mile or so. Also, after turning the car off when hot and then on it refuses to idle as well unless I mash the pedal a couple of times.

Thu May 25, 2017 6:07 pm

boom10ful wrote: asiab3 wrote: boom10ful wrote: Alright it's all adjusted now.

And you've run the procedure?

Yes, however I've almost about had it with this dam car :x. I've noticed that when I have it at a steady throttle that the RPMs will noticeably drop a bit. Is that normal? This happens when its parked and I'm manually giving it gas at the back.

I wouldn't care so much; we don't drive our cars in neutral.

Quote: It also still refuses to idle when the choke is off until it is driven a mile or so. Also, after turning the car off when hot and then on it refuses to idle as well unless I mash the pedal a couple of times.

Slooowwww dooowwwnnn a bit. What happened with the above procedure, word for word, when you use the fast idle screw (#1) instead of the big brass speed screw?

Robbie

Thu May 25, 2017 6:25 pm

asiab3 wrote: boom10ful wrote: asiab3 wrote: boom10ful wrote: Alright it's all adjusted now.

And you've run the procedure?

Yes, however I've almost about had it with this dam car :x. I've noticed that when I have it at a steady throttle that the RPMs will noticeably drop a bit. Is that normal? This happens when its parked and I'm manually giving it gas at the back.

I wouldn't care so much; we don't drive our cars in neutral.

Quote: It also still refuses to idle when the choke is off until it is driven a mile or so. Also, after turning the car off when hot and then on it refuses to idle as well unless I mash the pedal a couple of times.

Slooowwww dooowwwnnn a bit. What happened with the above procedure, word for word, when you use the fast idle screw (#1) instead of the big brass speed screw?

Robbie

I adjusted the fast idle screw to the point where I saw the needle moving then went back 1/8 of a turn. It now refuses to idle when hot. I have to step on the gas otherwise it shuts off when off the choke.