34 PICT 3 Adjustment Woes

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vwlover77
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34 PICT 3 Adjustment Woes

Post by vwlover77 » Fri May 05, 2017 8:26 am

34 PICT 3 carb with a DVDA distributor on a '71 Super Beetle. Running a 130 main jet.

I've verified that the vacuum advance and vacuum retard on the distributor are working. I have the timing set at around 10 degrees ATDC instead of 5 degrees as I read Colin's old post on that other site that this would provide smoother acceleration.

I'm following the Bentley procedure for carb adjustment by backing out the small volume screw until maximum idle speed is achieved and then turning the screw slowly clockwise until the idle speed drops slightly. No problems here.

However, when I then try to finally reduce the resulting idle speed back to 950 rpm (Autostick setting), I bottom out the large screw.

I hope this original Solex carb with new throttle shaft bushings is not messed up in some way..... Suggestions?

(I have already checked that the throttle plate is adjusted correctly and the choke is fully open).
Don

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78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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asiab3
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Re: 34 PICT 3 Adjustment Woes

Post by asiab3 » Fri May 05, 2017 9:12 am

Hi Don,

As a quick test, can you twist-then-pull each vacuum hose off the carburetor, and then suck on it? You should not feel any airflow; it should feel like a milkshake that is too thick.

Next, can you confirm that your timing is set ATDC, and not BTDC?

Next next, can you confirm with a picture from an owner's manual or service manual, that your hoses are hooked to the correct nipples on the carb?

Good luck!
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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vwlover77
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Re: 34 PICT 3 Adjustment Woes

Post by vwlover77 » Fri May 05, 2017 11:58 am

The timing is set ATDC. Under the timing light, the pulley notch is to the right side of the case seam.

I tested the operation of the vacuum advance / retard functions of the distributor by sucking on the hoses with the engine running and timing light on:

- Large green hose from center "front" of carb to back of distributor vacuum can (vacuum retard)
1. Engine idling with timing mark at 10 degrees ATDC
2. Remove hose at carb. Timing jumps up to around 5 degrees ATDC and idle speed increases
3. Suck on hose. No leakage, timing mark moves back right to the 10 degree ATDC position, idle speed drops.
4. Reconnect hose

- Metal tube with small hoses on either end connected to left side of carb and front of distributor vacuum can
1. Engine idling with timing mark at 10 degrees ATDC
2. Remove hose at carb. No change in timing mark or idle speed.
3. Suck on hose. No leakage, and timing mark moves approximately to the 10 degrees BTDC position (left side of case seam). Idle speed increases.
4. Reconnect hose.
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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wcfvw69
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Re: 34 PICT 3 Adjustment Woes

Post by wcfvw69 » Fri May 05, 2017 8:38 pm

What size pilot jet and air correction jet are you running? A 130 main should be fine. Have you checked for vacuum leaks out of curiosity? How are the little o-rings on the bypass screw and volume screw? No leaks there? When I set up my German Solex 34-3 and DVDA, I set it to 5* ATDC with both hoses connected. I then will use the bypass screw to fine tune the idle speed. Finally, I'll adjust the volume screw like you did. Once I'm satisfied with that, I'll finish with the bypass screw to set the final idle speed.

My experiences with these 34-3 carbs is they are finicky if EVERYTHING isn't set correct. The float height has to be set correctly. The fast idle needs to be set perfect. All the passages in the carb need to be clean. They like no more than 3psi fuel pressure.

On your distributor, I'm not a fan or advocate of the suck on the vacuum hose test to check the vacuum cans health. You can buy a hand vacuum pump w/a gauge for $20. I restore and sell a lot of DVDA's. Most of the vacuum cans would pass the tongue/suck on the hose test. When I put my hand pump on them, 99% of them fail and won't hold a vacuum. Just an FYI on that. The other thing is the DVDA. Has it ever been serviced? Taken apart, cleaned, inspected and then re lubed? Every DVDA that I've disassembled for the first time since new, needed a thorough cleaning and re lube.

I had a German Solex 34-3 that would not idle with the pilot jet screwed in snug. I had soaked this carb in Berryman's carb cleaner. I blew all the passages out with carb cleaner and it still wouldn't idle. A wise poster on The Samba said you can't clean all the small internal passages out correctly w/out an ultrasonic parts cleaner. I bought the $70 dollar Harbour Freight unit. Now, this carb was spotless when I put it in the hot (140*), soapy water in the ultrasonic cleaner. After 10 minutes, the clean, soapy water was black! I ran the carb in there for an hour. When i put it back together and on the bus, it idled perfectly.

http://www.vw-resource.com/34pict3.html

This is a decent write up on adjusting the carb and other information on them.
1970 Westfalia bus. Stock 1776 dual port type 1 engine. Restored German Solex 34-3. Restored 205Q distributor, restored to factory appearance engine.

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vwlover77
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Re: 34 PICT 3 Adjustment Woes

Post by vwlover77 » Sun May 07, 2017 5:35 am

Thanks for all the good advice.... I will check the other jets when I get the chance and plan on a complete distributor disassemble, clean, lube, and test soon.
Don

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78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: 34 PICT 3 Adjustment Woes

Post by asiab3 » Sun May 07, 2017 3:49 pm

Uhh, backup a second. AutoStick? Are you setting the timing in gear or in neutral?

I am completely fine with an automatic Volkswagen that idles above spec in neutral as long as the idle in gear does not go below the listed idle speed specification. For example, if you idle at 900rpm in neutral, and putting it in gear drops the idle down to 650-700, then I would raise the idle. We don't drive in neutral, and we don't have emissions testing (right?) so why bog the idle down so far in gear that we lose oil pressure and cooling airflow?

Someone on TheSamba read me the riot act for suggesting this, but I enjoy getting my head out of the Bentley manual from time to time and thinking critically about the physics of 45+ year-old automatic transmissions.

Robbie

Ps- the VW rescource page has a typo towards the end where they mix up the mixture and the speed screws after getting it right earlier on in the article.
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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vwlover77
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Re: 34 PICT 3 Adjustment Woes

Post by vwlover77 » Mon May 08, 2017 8:35 am

Oh yes, the dreaded / beloved Autostick. I'm setting the timing and idle in neutral. The Bentley does specify a higher idle speed setting for Autostick cars.

BTW, I drove the car for the first time yesterday with the timing set to 10+ degrees ATDC. OMG, what a slug. No power at all. I reset it to the notch on the back side of the pulley at the case seam, which I now believe to be the correct 5 degrees ATDC. Peppy again.
Don

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78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: 34 PICT 3 Adjustment Woes

Post by sgkent » Mon May 08, 2017 1:32 pm

all the smog gear and correct distributor advance have to be present -> and working perfectly for that retarded setting to work right. When it is the retarded position moves the second the throttle is advanced. If the smog gear or distributor advance are slightly off, or the throttle plate slightly off or worn the car will fall flat when one steps on it, and perhaps be awful to drive. Checking your mechanical and vacuum advance mechanisms would be in order about now because of the description you gave. Make sure they are working nominally so that your timing can advance and retard smoothly.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

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tommu
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Re: 34 PICT 3 Adjustment Woes

Post by tommu » Mon May 08, 2017 2:58 pm

How much impact do the SMOG components have on a DVDA / PICT 34 4 combination?

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Re: 34 PICT 3 Adjustment Woes

Post by asiab3 » Mon May 08, 2017 3:28 pm

vwlover77, have you confirmed that the "fast idle" screw is not over-adjusted? This would give a fast idle, and a lousy throttle response if the large brass screw was bottomed out to compensate. (# 1 below is what I'm talking about.) On a warmed-up engine, back it out until it is not touching at idle, then screw it in until it just BARELY touches the cam base.

Image


If you want to get experimental, note exactly where your idle is set to now, in neutral. Have a helper hold the brakes, and put the car in gear. Using the big brass screw, (#3,) raise the idle to 900-950 in gear, and then have the helper put the car in neutral. Count the number of turns you made. How high is the idle now? Go for a test drive and see how it does. If you don't like it, you can always set it back to where it was, because you counted the turns, RIGHT? ;)

--
sgkent wrote:
Mon May 08, 2017 1:32 pm
all the smog gear and correct distributor advance have to be present -> and working perfectly for that retarded setting to work right. When it is the retarded position moves the second the throttle is advanced.
Did you mean the vacuum retard backs off the second the throttle is opened? I think you did, but I want to make sure.
tommu wrote:
Mon May 08, 2017 2:58 pm
How much impact do the SMOG components have on a DVDA / PICT 34 4 combination?
A bit on deceleration. The DVDA itself was founded for emissions regulations, and it drives beautifully when paired and dialed in correctly. I'd wager that 99% of the VWs out there, even those with DVDAs, don't have the throttle positioner or EGR or charcoal canister hooked up. "Smog components" is a VERY vague term, so let's specify what we mean. For example, your 34pict3 probably won't idle without the idle bypass circuitry clogged or way out of tune. It might idle fast if the vacuum retard isn't functioning. It might backfire on decel without the throttle positioner. EGR was on later T1's only, so let's ignore that. And the charcoal canister reduces air pollution and won't noticeably affect your engine performance if missing. Do you have a more direct question that we could answer?

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: 34 PICT 3 Adjustment Woes

Post by tommu » Mon May 08, 2017 4:00 pm

asiab3 wrote:
Mon May 08, 2017 3:28 pm
A bit on deceleration. The DVDA itself was founded for emissions regulations, and it drives beautifully when paired and dialed in correctly. I'd wager that 99% of the VWs out there, even those with DVDAs, don't have the throttle positioner or EGR or charcoal canister hooked up. "Smog components" is a VERY vague term, so let's specify what we mean. For example, your 34pict3 probably won't idle without the idle bypass circuitry clogged or way out of tune. It might idle fast if the vacuum retard isn't functioning. It might backfire on decel without the throttle positioner. EGR was on later T1's only, so let's ignore that. And the charcoal canister reduces air pollution and won't noticeably affect your engine performance if missing. Do you have a more direct question that we could answer?

Robbie
To be more direct - I was interested to know if a Dashpot and Throttle Valve Positioner have a direct and noticeable impact on vacuum retard to advance transition or vacuum advance curve. It made wonder if I was missing components that impact pure drivability.

vwlover77 - I suffered the same symptoms with my PICT 34 3. My woes were caused both by the fast idle screw as Robbie describes and also by my (poor) valve adjustment technique. I couldn't achieve a good tune until I learnt how to adjust the valves consistently and accurately. When did you last check yours?

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Re: 34 PICT 3 Adjustment Woes

Post by asiab3 » Mon May 08, 2017 4:33 pm

vwlover77, to make sure this post is relevant to you, do you have any throttle positioner-related devices on your engine?
tommu wrote:
Mon May 08, 2017 4:00 pm
To be more direct - I was interested to know if a Dashpot and Throttle Valve Positioner have a direct and noticeable impact on vacuum retard to advance transition or vacuum advance curve. It made wonder if I was missing components that impact pure drivability.
Every engine is just different enough that I will answer cautiously… The dashpot and throttle positioner both slow do the throttle arm's return to idle. This delays the distributor vacuum retard from kicking in, which on a properly tuned engine just feels less jerky when suddenly releasing the accelerator pedal. On some engines, the throttle positioner can mask popping on deceleration.

The dashpot slows the arm's return like a spring, that's it, so it doesn't help on long decel events. The throttle positioner compares carb vacuum to intake manifold vacuum, and holds the arm out as long as it is tuned for. Some models even got both in '71, talk to busdaddy on TS about his bus that came with both, but my guess is that California delivery cars got both.

I've driven a few DVDA & 34picr3 buses that would drive fine, until you depressed the clutch and let off the pedal from a high RPM. They would dive down to about 500rpm, and then recover. I never checked their state of tune, but the throttle positioner (and perhaps the dashpot) would certainly mask this symptom.

Thread hijack over? :pirate:
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: 34 PICT 3 Adjustment Woes

Post by wcfvw69 » Tue May 09, 2017 5:50 am

What's more important than the dash pot and throttle positioner w/the DVDA and German solex 34-3 is that the carb and distributor match. There are a TON of Solex 34-3's with different base flange numbers on them made from 1971-1974. VW lover, have you checked your base flange number on your carb and then checked the distributor number? Solex/VW had a specific 34-3 for the autosticks as well.

My experiences with DVDA's and Solex 34-3's is they will perform fine w/out the dash pot and throttle positioners installed. As Robbie mentioned, they do return to idle quickly due to the retard function upon lifting off the throttle. I've reinstalled the dash pot and throttle positioner on my buses engine. It did help the engine return to idle in a more controlled way and not so rapidly. The good news is both the dash pots and throttle positioners are plentiful in the used parts market if you wanted to reinstall them. There is no downside in doing this as the parts are cheap. It's also rewarding to have all the parts in place as designed to get a true appreciation to how well these engine ran when delivered new.
1970 Westfalia bus. Stock 1776 dual port type 1 engine. Restored German Solex 34-3. Restored 205Q distributor, restored to factory appearance engine.

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Re: 34 PICT 3 Adjustment Woes

Post by vwlover77 » Tue May 09, 2017 7:10 am

The Autostick engines did not come with either the dashpot or throttle positioner. As it was explained to me, the torque converter prevents the sudden deceleration of the engine when the throttle is suddenly snapped shut. It's the sudden deceleration that results in high emissions.

My fast idle screw is properly adjusted using the procedure you noted.

I will check the carb base number and distributor number, but I believe both are original to the car.

Watching with my timing light, it's clear the vacuum signal that retards the timing goes away the moment the throttle is opened even slightly.

It's been a while time-wise since I've adjusted the valves, but I put so few miles on this car that it probably hasn't been more than 1000 miles. I always try to err on the side of a little too loose versus a little too tight. And I have the stepped feeler gauges which help a lot.

My neutral idle is set to around 1100 rpm right now and the car idles beautifully at around 950 while in gear. The large screw is no longer bottomed out at this idle speed setting.

(My reported idle speeds are estimates because my old dwell/tach is not working properly.)
Don

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78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: 34 PICT 3 Adjustment Woes

Post by sgkent » Tue May 09, 2017 8:37 am

I bottom out the large screw
sounds like you have looked at the setup carefully. If the above is the main thing you are concerned with there are only three or four things I know that can cause an engine to race like that.

1) The timing is sticking too advanced
2) There is an air leak into the manifold allowing the engine to run fast
3) The fast idle circuit is defective or out of adjustment
4) the idle return spring, cable etc are not allowing the engine to fully fall back to the idle stop, or the idle stop / throttle plate position screw is not adjusted correctly.

Be aware if this car has never run right since you purchased it that sometimes a common hack is to drill the throttle plate to let more air thru at idle on big displacement engines. VW did it on some carbs for other reasons. If the throttle plate is drilled, it may take some sleuthing on your part to figure what carb came on it originally and how the throttle plate was set up. Also make sure that the idle cut off solenoid circuit on the side has not been tampered with or leaking air.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

Merlin The Wrench

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