Question about carb, dist, and vacuum can correlation

[sb001]

I am trying to help a fellow poster over on VWAR diagnose a problem he is having with stumbling off the line and occasional stalling. He has a 71 Ghia autostick, but the same question would apply here.
Come to find out he has the correct carb (Solex 34 PICT 3), and correct distributor (113-905-205 AH) for his year model autostick. BUT he has the WRONG vacuum canister. According to the Bosch tuneup chart:

https://www.thesamba.com/vw/archives/manuals/Bosch_Tune_Up_Parts/Bosch_Tune_Up_Parts.pdf

the correct canister for his setup would be the 07092 DVDA canister (short number 853) which has a vacuum advance rating of 2-5° @ 240mm Hg, and retard rating of 11-13° @ 230mm Hg.

However he has the 07083 canister (short number 811) which came with the 1970 113-905-205 AD autostick distributor and the 30 PICT 3 carb, and is rated at 8-12° advance @ 240mm Hg and 6-8° retard at 170mm Hg.

I am pretty sure this is a large part of his issue. I know the different canister ratings correspond to the different carbs they came with, but can someone give a thorough explanation on exactly how this setup would affect his stumbling off idle, etc? I would assume the 34 PICT 3 had a larger throttle plate hole and perhaps other differences that cause it to produce more vacuum, therefore the setups it came on did not need a canister that was rated for as much vacuum advance- but I don't know for sure. BTW he DOES have the timing set correct @ 5° ATDC but would this setup affect timing as well?

Bottom line is we are trying to see if there is any way we can make his setup work with what he's got- not because he is lazy or cheap but because that 853 canister is almost impossible to find, and no other canister I see listed is rated for the same vacuum signals. Thanks
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[ashman40]

Here are my suggestions....
1) Confirm the vacuum retard is working correctly. With the engine running and warmed up at idle (800-950rpm)... check the idle timing with both hoses connected. You should read 5ATDC. Disconnect and plug the vacuum retard hose running from the rear of the carb to the inner vacuum nipple on the distributor (disconnect and plug the distributor end). You should see the timing jump from 5ATDC to 7BTDC (TDC mark should jump to the other side of the case split).

2) Check the vacuum advance. With the engine now idling a little high with around 7BTDC showing under the timing light because you disconnected the vacuum retard hose... connect the vacuum advance hose from the rear port of the carb (where the vacuum retard hose was connected) to the vacuum advance nipple on the distributor. Your vacuum advance is now running off of strong intake vacuum. This should immediately cause the vacuum advance timing to jump 8-12deg and now the timing should read close to 20BTDC.

3) Check your mechanical advance. Disconnect and plug BOTH vacuum hoses (timing should drop back to around 7BTDC). Slowly rev the engine while watching the TDC mark under the timing light. The TDC mark should rotate smoothly CCW until it is around where the fan belt leaves the crank pulley (around 30deg CCW from the case split). The timing mark should reflect the engine rpms. As you slowly increase the rpms, the timing mark should slowly move more and more CCW until it eventually stops moving regardless changes in the rpm (total advance). If you stop increasing the rpms along the way and hold a steady rpm, the timing mark should hold a steady timing w/o jumping around. Let the rpms drop back to idle... what is your timing reading now?

4) Confirm your carb has the correct flange stamping for use with a DVDA distributor. Here is Glutamodo's chart showing the base flange stamp makings and the distributors they go with. Mixing up a carb designed for an SVDA distributor with a DVDA distributor can cause issues.

_________________
AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[sb001]

Hi ashman, thanks very much for your response. I have linked this thread with your response over on VWAR.

BTW I spoke too soon-- there is an ad in the classifieds on here for the exact canister he needs:

http://www.thesamba.com/vw/classifieds/detail.php?id=1637579
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[airschooled]

5) Check accelerator pump output. Cheap-Os will look down the throat to confirm, scientists will measure with a graduated cylinder. The rest of us are somewhere in the middle.

6) Check intake manifold for freezing feeling on left side of down pipe. If very cold, confirm that heat risers are clear, and warm air intake is functioning properly. Where is the climate of the OP?

Good luck, thanks for helping out the community,
Robbie
_________________
Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
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[wcfvw69]

Another factor with those DVDA's is their condition. I've restored a few dozen of them now. Each one that I've disassembled have had sticky or frozen advance/retard pivot plates. After 40+ years, the original grease is hard, sticky and mixed with the dirt and debris. The centrifugal weights can be sticky as well. The internals of the distributor need to be cleaned, oiled and greased again.

I just rebuilt a German 034 SVDA a couple of days ago. The pivot plate that the vacuum can arm attaches to was almost frozen. The vacuum can had failed probably due to the extra effort to move the plate.

If you're running the correct base flange number Solex 34-3 carb that matches a DVDA distributor, I'd get that one restored and source an NOS vacuum can for it as well.
_________________
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[jovanybg]

sb001 - you rock!!!
Thanks a lot for your help and for the help of the other samba members!
What a great source of knowledge in our effort to keep these beautiful cars on the road!!! And what a great vw community!!!!
I really appreciate your help!
I will go ahead with the tests suggested in this post this weekend and will hope the canister sb001 found on here would arrive next week for more and hopefully final tests!!!
_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[jovanybg]

I've got the new, correct vacuum canister and finally was able to install it.
After installation I cannot time the engine correctly!
Static timing at 5 ATDC leads to no start - I have to time it at about 30 BTDC in order to start the engine. After it warms up, I am gradually trying to turn my distributor to make it to the 5 ATDC mark, but the engine starts to run unevenly and eventually dies unless I turn it back towards 30 BTDC!
After numerous tries I've started to doubt everything!
Attached pictures show that the distributor drive shaft groove is not at the exact position when the engine is at TDC (at least when the dimple on the crank pulley is at the crack of the engine).
On top of that it seems as I've had the rotor pointing at #1, but I had it connected to #3 spark plug (attached pictures). That is how the car have run for the last year with the incorrect vacuum canister....
Do I need to remove my spark plug #1 and drop a pencil in there to make sure I am at TDC on Cylinder #1?! Right now I am doubting everything!
How was possible to run like that until I swapped the distributor vacuum canister?!

_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[jovanybg]

....and I've just removed the spark plug #1 and in the position showed on the above pictures I've dropped a pencil with the eraser side down to the Cylinder #1. I've then turned the pulley a few degrees left and right to make sure the cylinder is at the TDC when the dimple is at TDC position! The pencil came all the way out, stayed there for a few degrees right at when the dimple was at the engine crack.
Now I know the above pictures show TDC and the distributor rotor is aimed at the distributor mark and it points at Spark plug #1.
BUT I have spark plug #3 connected there!!!!!!
How it was even possible to run the engine like that?! On top of that it run pretty good with only a little hesitation and low rpm when stopped in gear (autostick car).
_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[sb001]

Hey jovanybg,

What has happened is that someone at some point installed your distributor drive gear 180 degrees out from where it should have been. This is NO BIG DEAL.

Here's what is happening: Because your distributor drive gear has been installed 180° out of whack, basically, when you think you are at TDC for #1, you are actually at TDC for # 3.

But wait you say, I tested that I was at TDC for #1 using that pencil test! Well here's the problem with using that test method just by itself: TDC refers to where the piston should be at the top of its travel for its compression stroke. But remember, since this is a four stroke engine, each piston reaches the top of its travel stroke TWICE- once for compression stroke and once for exhaust stroke. So when you did your pencil test to confirm that you were at TDC for cylinder #1 with everything set as it is in your pictures above- you actually were checking cylinder #1 at the top of its EXHAUST stroke, NOT at the top of its COMPRESSION stroke.

Because each piston can be at the top of its travel TWICE, this test method by itself is sort of inconclusive- you have to also visually verify that the valves for that cylinder you are testing are in the correct position as well. When you are looking for TDC at #1, your intake and exhaust valve rockers for #1 should both be pulled out away from the valve stems so that you have .006 gap between the top of the rocker and the valve stem.

Look at this picture showing a VW engine at TDC for cylinder #1:

You can see how the tops of the two rockers for cylinder #1 (along with the intake valve rocker for cylinder #2) are pulled out away from the valve stems. Compare this to the exhaust valve rocker for cylinder #2 on the far left. See how that one is pressed inward against the valve stem?

This picture shows what you want to see when you are actually at TDC for the compression stroke for cylinder #1. I'd be willing to bet, leaving everything exactly as it is in your pictures above, if you checked the rockers on your cylinder #1 you would see that they are rotated more inward against the valve stems than what this picture shows--BUT, if you went around to cylinder #3 and had a look, you would find that the valve rockers for #3 are positioned exactly like the rockers for #1 shown in this photo.

SO what does all this mean in terms of your engine running? It will not affect the engine in any way, except that (as you have already figured out) you need to plug the spark plug wire for cylinder #3 where you would think the plug wire for #1 should go. (And the plug wire for #1 would go opposite where #3 is.) The plug wires still rotate around the distributor cap the same way (1-4-3-2 clockwise.) It's just that they will all be 180° out from where they would normally be. Your engine will still run perfectly this way.

Then, to set timing, rotate your crank pulley one revolution around from where it is in your picture above. This should bring the 5° ATDC mark back into alignment with your crankcase seam but your distributor rotor will now actually be pointing to spark plug wire #1. NOW you can set timing using your timing light because you will actually be on TDC for the compression stroke of cylinder #1.

Now, you COULD fix this if you really wanted to, by buying a distributor drive gear puller (it's a little cylindrical contraption that you stick down the distributor hole and pull the drive gear out with), pull out the drive gear, rotate it 180° and reinsert it. Then everything would line up the way it's supposed to. But-- it's not really necessary at all unless you just want everything to be perfect. You can just leave it as is and install the plug wires as you have them and the engine will run fine.

As far as the engine, how does it run now with the correct vacuum canister on there-- can you time it better and tune the carb better??
_________________
I'm the humblest guy on this board.

1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor

[ashman40]

[jovanybg]

The timing with the new vacuum canister was impossible to achieve.
I've had to rotate the distributor until about 30 BTDC to have the engine running. If the engine is cold and I time it at 5 ATDC it stalls.
Yesterday when the engine was hot I was able to time it at 5 ATDC and the problem with the generator light was not present when I've put it in gear (but only in the garage, no driving involved).
Today I've tried to start the car as I left it yesterday and I couldn't. Had to rotate the distributor to have the mark at 30 BTDC in order to keep it running.
That is the reason why I've started doubting everything for the timing - position of TDC, position of distributor shaft and so on.

Should I go ahead and check the valves on Cylinder #1 to confirm if I am at compression or exhaust stroke?
If I am at compression - I will have to swap the wires from #3 to #1 and so on....
But if I am at exhaust stroke everything should be correct timing wise, but the car would not want to stay running if timed at 5 ATDC.
_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[Starbucket]

If you removed the dist. to install the can, then you put the dist. back in wrong and/or did you compare the arm lengths of the two can.s to see if they were the same length? Insure both valves adjusters have clearance when you THINK you are on #1 then make sure rotor is pointing to the notch on dist. where #1 wire goes. That's TDC of #1. Check the plug wires at the plug and cap for tightness and correct firing order.

[sb001]

[sb001]

[jovanybg]

Here is how the valves are right now with all the above pictures still actual!
Only the very outer rocker (on cylinder #2) is moving and the valvehas a huge gap of 0.009!!!!
All other 3x rockers do not move.
That will mean I am actually at TDC for Cylinder #1 if I read all the explanations above correctly.
A simple swap of the spark wires should do the trick?!
_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[sb001]

[jovanybg]

After turning one rotation of the pulley I've got all 3 front rockers with some play and only the very last rocker locked in place.
Now I am at where I've started!
Static timing at 5 ATDC before starting the engine, but not able to keep the engine running, unless I turn the distributor so the 5 ATDC notch is at about 35 degrees to the left of where the split of the engine....
Can something be wrong with the vacuum canister, so it doesn't time correctly?

_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[jovanybg]

And just to post the new vacuum canister mounted on the distributor before I put it back in the car.

_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor

[sb001]

[jovanybg]

Everything is as it was with the old vacuum canister now.
The rotor is 180 degrees from the mark on the distributor and is aiming at #1 wire.

_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor