74 Super bogs down when shifting

[Connie74]

Happy January! Last week the Super started having problems when upshifting. I had been running fine for about 3 weeks after doing a full tune up (valves, timing, carb) so I am a bit miffed. The motor boggs down when upshifting or starting out from a stop, and I have to rev it ALOT before I let the clutch out, and then it really wants to die and I have to take my foot off and kind of pump it progressively more, while releasing the clutch until the motor "catches up". 34 PICT 3 with SVDA. I did change the dizzy and cap when I did the tune up because the car would sometimes just turn over without firing up, and then eventually catch and run. So, new cap and rotor got it back into shape, but now she is just really hard to keep running when upshifting. Tonight I did a rebuild kit, and cleaned all of the jets and ports with chemtool. Starts like a champ, idles fine, timing is solid, good stream from accelerator pump, but the issue with laboring during shifts is...driving me crazy. Any opinions are appreciated. PS - it is really really cold here. I disconnected the choke and wired back the butterfly so the choke is inoperative (has been for years). Thank you in advance!!!

[baldessariclan]

[Connie74]

Thank you, baldessariclan
I don't use a choke, just do it all "by foot". Once it gets fully warm it will idle fine, and timing is really good, as well. Living choke-less is something I am trying this year, so far it is working out fine and temps have been down to the t-t-t-t-teens! I will add, to the previous, that even sitting still I can move the throttle fast enough to duplicate the stutter and stall, so it is not JUST when driving that the stall can happen. I know one way to check the vacuum advance pot is to suck on the open vacuum tube and hold your tongue on the end once some vacuum is orally established. I noticed that it takes (I think) alot of suck to get that base plate to rotate, but then it holds the vacuum against my tongue for more than the standard 5 seconds. However, when the motor is running I can hold my finger over the other end of the tube (with one end hooked to the side port on the carb) and hardly feel what I think would be the same amount of vacuum from the carb that it took for me to suck that base plate, even at high rpms. Should I just get a vacuum gauge and see what the vacuum is actually drawing, or maybe do some base plate maintenance?

[wcfvw69]

I'm curious what brand carb and distributor are you running? Are these original restored German parts are or they new carbs and distributors?

I'm not sure why you're not using the electric choke as well? Does this engine have a thermostat and flaps installed?
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[baldessariclan]

Like Bill said above, would be helpful to know some more specifics & details on the distributor and carburetor you’re running in your car, plus what timing setting you’re using, etc. Post some pics too, maybe?

You can get a vacuum gauge (or even better, a vacuum pump + gauge combo) to test your distributor’s vacuum advance performance. Here are the specified advance curves for a 205 AJ distributor (ref below) — your SVDA distributor will likely use a similar vacuum advance curve. Centrifugal advance curve is at top (marked “b”), vacuum advance curve sits below it (marked “a”), and vacuum retard curve is on the bottom (which you can ignore, in this case).

Note that the vacuum units shown on the chart are in mm Hg, so you’ll likely need to convert those numbers to PSI or MPa (or whatever units your vacuum gauge uses). Also, the degrees of advance and rotational speeds shown in the chart are with respect to the distributor itself — the actual engine speed and timing advance / retard will be double the values shown.
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1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[tzepesh]

At idle, there is no vacuum coming out of the carb. It only appears once you apply some throttle. It is ported vacuum, not manifold vacuum.
Did you check the accelerator pump? You can just take a look inside the carb and apply quickly some throttle, engine off. There is a small brass tube inside, you should see gasoline being squirted down.
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[Connie74]

Thank you all for posting! The vacuum curves are pretty cosmic, so thank you. The carb is 34 PICT 3 and the distributor is 043 905 205C, SVDA they are matched well because she ran like a rabid squirrel for many years, and then....she doesn't. The accelerator pump is working well. Timing at idle is at 7.5deg BTDC. I have wired the choke back because Muir suggests that it is a convenience more than a necessity. I want to see if that is true. This evening I put the inductive timing light on each of the spark plug leads and they are all sending spark. I did grab the #4 lead at the top of the spark plug and it was not seated all the way. I seated it, checked timing (solid) then test drove it again, and there was a slight improvement in take off power from a stop (and uphill) but still really really poor performance with any demand on the motor. Your continued support is appreciated. I have to get my daughter to snap some pics since I am technologically challenged (no smart phone), but will do so if you think it will help.

[jinx758]

I need some clarification please.

The distributor # you posted as an SVDA is listed as a DVDA on VWnos & available for $185usd.
Some only use vacuum advance on a dual vac distributor. Proper hose placement is critical for optimum performance.

Your timing is not ideal at 7.5* ... this is a universal setting to allow for warm up before disconnecting advance vacuum, plugging hose & setting advance to max out around 30*.
You are missing out on both performance and driveability.
7.5 is for idling, not driving.
My "034" is at 30* all in & falls to about 9.5-10* at idle.

Triple & quadruple check your firing order - these quirky engines will idle with 2 or more wrong but will suffer when on throttle (after tune up is the time for things to go south ) .

With cap & rotor off twist shaft & let go several times.
Is it difficult to rotate or feel gritty ? It should also snap back quickly.
You put 2 drops of oil on felt inside shaft well under rotor, yes ?

You posted PICT3-4 but that is a model #.
wcfvw69 asked the brand ... empi, solex, brosal, & etc.

Please post pics of current engine bay & a few angles.

We're here to help ... stay safe

jinx

Edited cuz I'm a doofus ...
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1971 Standard Bug
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38mm EGAS Carburetor

[heimlich]

It sounds like you have a 009. I'm wondering if your vacuum canister has a hole in it or leaks. Do you have a hand vacuum pump you can put on the distributor vacuum canister to check if it advances?

If you have one of those aftermarket vacuum canisters throw it away. They are junk and will cause you more problems than just buying a good German one.
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[baldessariclan]

W/ regard to your problems as you’ve described them, I’m still the most suspicious of your distributor’s advance function performance, plus the lack of choke function on your carburetor. Either of those can cause serious hesitation and/or lack of power issues.

Am aware John Muir advocated against electric chokes in his “Idiot” manual, but that advice seems relatively outdated, and especially questionable for later model Beetles w/ the 34 PICT-3 carbs. Until the engine is fully warmed up, you’re definitely going to have some degree of stumbling and low power issues w/out any choke (assuming more-or-less stock engine setup and tuning). And if your car is missing the thermostat and flaps, the warmup period will take that much longer in cold weather (if it ever even fully gets there at all…).

And I always like to verify everything is working properly w/ the ignition components, prior to moving on to fuel system troubleshooting. Weak spark and/or improper advance can rob your engine of serious amounts of power — and Beetles don’t have much of that to spare in the first place!

So yeah, make sure that distributor is working properly, plus check your plugs, points, coil, condenser, wires & connections, etc. Plus consider getting your choke back into proper working order as well. Good luck!
_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[Root_Werks]

Got a picture of the engine you can post? Might help identify some things.

Others have already said, really shouldn't idle cold with no choke/fast idle if timed and tuned correctly.
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When I set my timing, why do I flush, then take a pee?

[Connie74]

Thank you all! I have some fun lined up for tomorrow, checking these items. I did get down and suck on the vac advance line while the engine was running and that did show some advance on the timing light/rpm I have. So, I will forgo the "no choke" experiment and get that thing working, then do a tune up from the valves on up, then check the activity in the distributor as jinx suggests. Jinx, I think you are asking for me to spin the dizzy shaft? If I am parked then I suppose the shaft won't spin, but the advance plate should move smoothly as I twist, then snap back rather than creeping like it is covered in thick, deliscious heavy molasses in January, right? I will see how that performs. I like the comment about timing...thank you! When the motor is all in (3000 rpm) then THAT is what I set the timing to, and wherever it falls at idle is...just wherever it settles, so it being at 7.5 may very well mean that I am not advancing enough at the "all in". SHIT shit shit. I feel that may be the critical item, here, BUT I will crawl around doing all that other stuff (except for the vacuum pump thing unless someone in the local club has one....) Thank you all. I will send some pics since I am a bit confused about the distributor numbering system. I thought that the 009 was a mechanical-only dizzy?

[heimlich]

009 is the infamous mechanical only distributor. It is the one that usually elicits the hesitation with a 34 pict 3.

If the vacuum is moving the plate in the distributor you might be ok.

I would check/change the condenser. It can cause gas like problems.
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[Mikedrevguy]

Are the heat riser tubes connected and clear?
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79 VW Iltis
69 Bwajaja
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[Connie74]

[heimlich]

You've got a nice engine. If it was working you need to figure out what changed or broke that is causing the issue now.

You can throw parts at it. Some people are going to tell you because something isn't original that you need to change it. That is not going to solve your problem other than cost you a lot of money to swap out parts that were at one time working. When you are ready to replace a part you can then spend the money at that time buying the correct one. Your distributor is a good one except for the aftermarket vacuum canister. Your carburetor is original. Your fuel pump might be lacking. If they aren't broken don't fix them.

For your issue your most likely culprits are the carburetor and distributor. The distributor is easy enough to diagnose. All you need is a timing light with RPM. Hook the timing light to the 1st spark plug wire. Then you can map out the curve of the distributor. I'd recommend checking the advance at 3,000 RPM. Kick it up to 3,500 momentarily just to see if it goes higher.
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[wcfvw69]

If that was my bug, I'd do the following to diagnose what the issue is-

1) Check the fuel pressure of your economy aftermarket fuel pump. Some of those pumps can put out WAY too much fuel pressure and cause flooding issues and some of your symptoms. You don't want more than 3.5 PSI with that German 34-3 carb. The original VW pumps put out 3 PSI. If you're pump is bad then you need to replace it with a good one that puts out 3 PSI.

2) Verify your distributor is mechanically advancing with a timing light. Hook up the timing light. Start it up. Un-plug the vacuum hose on the canister on the distributor and plug it with a pencil or golf tee. While pointing at the timing mark on the case, rev the engine and see how much the mechanical timing is advancing. At idle the timing should be lined up at the 7.5° BTDC mark on the pulley. When you rev the engine the timing should advance another 21-22° mechanically. There are a bunch of threads that show you how to mark you pulley at say 30° BTDC.

*If the distributor is advancing correctly, you need to get a hand vacuum pump with gauge or mighty vac. They are $50 ish dollars on Amazon. Connect it to the vacuum canister and pump it up to 200 MM hg of vacuum. Then stop and watch the gauge. It should not leak down. There are some poor quality aftermarket vacuum canister but also good ones as well.

*If it passes this test and your distributor is working correctly and your fuel pump is good, then I'd look at electrical causes.
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40+ years of VW repair, and VW parts and vehicle restoration experience.
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**Restored German Bosch distributors for sale or I can restore yours**
**Restored German Pierburg fuel pumps for sale or I can restore yours**
**Restored Porsche fuel pumps or I can restore yours**
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[Connie74]

Thank you all again. I am always a bit leary about doing stuff to the Super when I don't know where to start, but the knowledge and encouragement form this forum is really powerful!
So, I did a bottom up tune up and found #1 intake needing a very very small adjustment, all others were where I left them last month. Yippee!!

heimlich, thank you for the comment. I try to keep her insides in shape. She gets me everywhere I need to be, every day (except when I ride my bicycle).

I re-armed the choke, baldessariclan, and I was amazed at how easily it started! The temp was down around 36 deg when I did this, so it was nice to have that bit of convenience. Thank you!! Warmed her up nicely, too!

But I did all that after I checked the dizzy shaft like jinx recommended. Smoothly rotating (about 10deg??) then smoothly snapping back. Checked the gap while there also, and it was where I had left it.

After the warm up I checked the timing. Plugged the can and the carb where the vacuum advance tube should be, and I was only getting 20 deg of advance at 3000 rpm. oops! So I turned it up to 32 deg at 3000 rpm, then attached the vacuum advance tube, and got 32 deg at 2400 and 38 deg of advance at 3000. Now idles with 10.5 deg advance.
Tuned the carb...
Now I gotta say that getting the idle down to 900 is kind of weird. I always feel that the motor is about to stall that low, but, it did not. Like a huge singer sewing machine at that rpm.

The road test was really satisfying. No bogging down, and I was pleased that at stop signs the motor didn't stumble, just dropped down to 900-ish and held steady. WOW!!

One question for heimlich. Once the rpms get above 3000 there doesn't look to be much advance but it is hard to tell since the timing mark does not hold steady, but becomes a blur about 1/4 inch wide. Is that normal?

I am back to driving happy and I have you all to thank!

[heimlich]

[ashman40]