34 PICT 3 Adjustment issues

[Yehan73]

Hi Everyone. I have a 72 SB with a 34PICT 3 carb. The problem is when I turn the larger scred pictured here all the way clockwise to a rest, the engine still runs? Because of this I can't get past the step 4) listed below.

The followig is the tuning process I have tried
1) Turn the fast idle screw touching the cam and 1/4 turn in
2) Turn small screw and the large one 2 1/2 turns fro rest
3) Trun the samll screw clockwise until you reach the fastest idle and turn until it drops another 200rpm.
4) Turn the large screw clokwise until you get the proper idle 900rmp

[Cadaver]

[wayne1230cars]

[Cadaver]

x2 all

yes,step in is faulty in your post OP
attach tachometer so you can see 30rpm drops that humans can hear.
1: timing set to spec. setting carb with bad timing is USELESS.
2: hot motor, fully hot.
3: choke, 100% open,, if not?, fix that first.

motor must be hot
when not hot the choke is active
when choke is active the choke fast idle cam is not as showing
in YOUR photo, its on the FAST idle steps
and when that is active, then the air is coming past the
main throttle valve butter fly plate, making the idle air screw , mostly
useless.


and best of all , see the training film chapter 2, YOURS,

http://www.youtube.com/watch?v=KWdZSr7x81w&feature=player_detailpage#t=98s
no air leaks, none period.
and no mods to the fly plate

Hit Control +F5 to refresh my page, i edited it greatly
to show the HOT PATH through the carb. I like photos, its easier
to show things and how they work.

ask questions. lots,
we can find the leak if you tell us or show real photos
i suspect yours above is a STOCK photo (copied from somewhere)
show yours, and we can see if things are wrong.

here , better

_________________
for sale now.
in Samba classifieds....1968 T1.

[Cadaver]

all air leaks
not from carb are illegal
same with EFI, non metered air.

the carb feeds fuel based on air it measures (eduction principles)
if you bypass that, it then goes lean.
vacuum lines cracked, open, missing, or diaphrams cracked.
gaskets bad.
boots bad.
even the heat riser tube can fill with water, and crack and breach the induction
2 posts this year just from that ODD fail.
suck one end , block the other 2, and it must not leak.
induction removed. (this is called a leak down test)

keep an open mind about fails, only fate rules this world.
not me, not the FSM or the book of statistics.... sorry this is the real world.

in a real shop we use a smoke machine, hook it up and bingo, end magic.

youtube that for a cheap DYI way.... simple as cherry pie.
a diesel glow plug and some oil and ......
_________________
for sale now.
in Samba classifieds....1968 T1.

[Yehan73]

Thanks guys. I suspected air leaks too. I will test to make sure the throttle shaft or other leaks are not present before I attempt any of the other adjustments.
Currently the Dwell and the timing and valve adjustments are spot on.

[Donnie strickland]

If your jets are dirty, turning the big screw will have no effect. If you eliminate any air leaks and you still have this problem, a carb cleaning is in order.

[jzjames]

No one ever mentions the rubber O rings on the air bypass screw. Wouldn't this affect something? (like if it's chewed up or something?)

[Yehan73]

The rubber o rings were by first suspects too. I teted with some saliva over the hole and reved the engine. Nothing got sucked in. So the seals are good there.

[Donnie strickland]

[Cadaver]

if the carb is leaking air fix that.
if the idle paths are blocked clean them (they are not)
(yes that spit tests are valid, as is greasing it with silicone grease)
if the intake leaks it goes lean and idle will be out of control.
in effect, the leaks cause the carb to loose control."illegal air"

the carb is the only valid source of air. if not , all bets off.

some carbs are modified, is yours?, did you look at the throttle butterfly
plate to see if it was modified, some do that so they can run the wrong dizzy.
all this takes tests and close looking... speculation is out.(save leaks)

if that valve is packed, the car will not idle at all, the vw training film even
mentions that. it is the only source of idle air. in the 34.
in fact, that is its Unique design change !, over the old 30Picts1,2 's

the old carb, THEY, used a throttle stop screw to set hot idle, this holds
the throttle valve open to keep idle and idle air.
Unique:
on this carb the throttle plate is 99.9% closed,
that leaves only 1 source of idle air!
if you close that valve and it still idles?, you just SAW illegal air. in action.
in a shop we plug in a smoke machine. (oh my, the base gasket is blown...)

you dont have one. so must do it the hard way, Inspections.
nor the ultrasonic leak detector. but ive used a rubber host to my
ear and found many an vacuum leak, sure have.. .for 50cents

its sucking air. and the carb is not the source.
(not i assume vacuum nipples are not leaking, nor the welsh plug blown out)
eg: pinch the vacuum lines, and makes sure not one vacuum block nipple cap
has cracks, and that the body of the car in not breached.
on some years there is the welsh plug on the side the gets loose.
and leaks air. (not sure if the 34 has the plug. but is just a steel disc)
happy hunting....
_________________
for sale now.
in Samba classifieds....1968 T1.

[hylomatt]

When you're adjusting the small, mixture screw to get the fastest idle, do you continually readjust the large volume control screw back down to the correct idle and keep adjusting the mixture screw out, going back and forth?

Or do you set the idle with the large screw and then adjust the mixture screw out as far as necessary one time and then reset the idle to be done?

If I go back and forth between the screws, I can continually keep getting a faster and faster idle to the point where my mixture small screw is turned out 5-7.

[AlmostHeavenWV_VW]

Being that this is a 7 year old thread, you may not get many responses.

The 34-3 should be adjusted as outlined in the beginning of this sticky thread:

https://www.thesamba.com/vw/forum/viewtopic.php?t=56411
_________________
1973 Standard Beetle
1600DP AK case
Solex 34PICT3 Carb
Bosch DVDA 205AJ Distributor

[hylomatt]

Okay, sorry, was trying to reuse instead of start a new thread. I'd have read that one.

[AlmostHeavenWV_VW]

From what you are describing, it doesn't sound right. The carb should 'settle' into proper adjustment with only a few 'back and forth' between the two screws.

[hylomatt]

I wanted to try to return the bus because the idle seems a little too uneven. I can hear a serge in the idle. I'm not sure how steady and consistent it should be though.

No vacuum leaks, spraying starter fluid around the intake castings, silicone boots, intake to carb connection point and the carb throttle bushings. The carb is a relatively new rebuild from VolkzBitz.

This is a 71 with the dual vacuum ( no leaks )
Timing: 5 ATDC
Dwell: 51
Last valve adjust: ~1100 miles ago
Pump Pressure: unsure (will measure)
Distributor: 211-905-205Q (rebuilt by Tasb)

Runs well but I'm unsure about the mixture. She runs around 220F-240F @ 65-68 MPH. I mention that because I know running lean can increase temperature. I'm about to take her up to the mountains at the end of the month, from Florida to North Carolina, up into the mountains a bit.

[AlmostHeavenWV_VW]

[hylomatt]

@AlmostHeavenWV_VW, again, sorry but I saw this thread about 34-pict-3, outlining the steps and I thought it would be a good place for clarification. I didn't take notice of the category it was in.

This is a 1971 Bus and it's the correct combo for my carb flange # and distro.

The carb and distro are less than 2 years old, maybe > 1 yr. No leaks around the shaft and no discernable play either.

The distro vacuum can has been tested and both sides work well and the points plate moves freely.

The dwell is a pertronix module so it doesn't really change.

Timing is conducted with the hoses on for this year, model of parts, etc. Green hose for retard, black smaller hose for advance.

Maybe serge isn't the right word but I can hear the RPM changing, rolling up and down repeatedly. Not by much, I'm guessing back and forth between about 840 - 900.

Good idea on that quick test for mixture condition. I'll do that.

[AlmostHeavenWV_VW]

No need to apologize, sir. I feel the category doesn't make a difference- after all it's the same engine, right?


I would like to correct myself. I was thinking of the 022905205Q. My mistake on the distributor. Sorry about that. Clerical error.


I would get a diagnostic tach on it to see if the RPMs are just wavering a bit or if the RPMs really are going up and down significantly. If you are keeping the RPMs within a 60RPM range- that's pretty good! After all, we are working with non-computerized, carb and mechanical distributor-ignition systems in these ACVWs.

Just for clarity- dwell cannot be measured with electronic modules. You may get a reading, but as you said it's not adjustable in any sense. I could be wrong, but I'm not even sure the reading is accurate or diagnostically meaningful.


Feel free to post back here if you continue to have issues. Like I said, the engines are the same!

Happy bus'n! I hope you don't get rid of the bus just for a simple idle issue.
_________________
1973 Standard Beetle
1600DP AK case
Solex 34PICT3 Carb
Bosch DVDA 205AJ Distributor

[hylomatt]

@AlmostHeavenWV_VW, ok yeah I've been driving around all day and haven't had a chance to do the hand/carb test. Tomorrow I'll do that test, make sure the throttle cable is sufficiently loose (I think it's a little too tight after the adjustments I did this morning) and make doubly sure the fast idle adjustment is correct too.

I wouldn't get rid of the bus. I'd drive it up to see VolkzBitz in WA or hire Amskeptic before anything like that happened. My first car was a 73 super beetle and after 8+ years of fussing with that worn out 34p3, I have patience for this kind of stuff