| bluemagman |
Mon Nov 16, 2009 11:02 pm |
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Greetings Samba. I am new to Beetle but not to auto repair. I have a 72 1600 DP fresh tune up 0 degrees advance new fuel pump/filter and a new 34pict3 carb. The car runs fine except for a flat spot or hesitation at low rpm. If you press the accellerator slowly the car will stall
Thanks |
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| bnam |
Mon Nov 16, 2009 11:30 pm |
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| Which distributor are you using? the stock DVDA was set to 5deg btdc I believe. |
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| Lingwendil |
Mon Nov 16, 2009 11:30 pm |
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| What distributor is on there does a lot for drivability on these cars. Which part number distributor do you have on there? |
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| bluemagman |
Tue Nov 17, 2009 9:39 pm |
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| I don't know the number on the distributor but it has two vacuums on it. |
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| bnam |
Tue Nov 17, 2009 10:02 pm |
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If you mean that it has one vacuum canister with 2 hoses on it, then it probably is the stock DVDA distributor. Check if vacuum can is working -- suck on a hose and see if holds the vacuum. Also, 0 deg is not the correct timing.
B |
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| ashman40 |
Thu Nov 19, 2009 6:16 am |
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Welcome to TheSamba. I was like you. I have a fair bit of background in American Iron V-8s. My biggest suggestion to you would be to forget any assumptions you have on how/why things work on acvws. They DON'T work the same way as 75% of "other" engines.
The 34PICT-3 had a few variations over the years to match different distributors. If you have a "new" one it is probably an aftermarket one. If so, take it apart and clean it and blow out all passages. Many are known to come from the factory with dirt/dust in the passages.
Also, it may not be an ideal match to your distributor. The jets and throttle plate holes may be different than your original carb.
The Dual Vacuum Dual Advance (DVDA) distributor are the later emission distributors. They had a vacuum retard (yes, retard) that activated at idle and the vacuum advance did nothing at idle. Once the throttle opened just a little the vacuum retard lost vacuum causing the distributor to advance as soon as the throttle opened. Also, the vacuum advance port in the venturi was exposed on throttle open and created more advance. Mechanical advance added more advance as the rpms rose.
This may be different than other distributors you may have worked on. |
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| Inane Cathode |
Thu Nov 19, 2009 9:50 am |
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ashman40 wrote: Welcome to TheSamba. I was like you. I have a fair bit of background in American Iron V-8s. My biggest suggestion to you would be to forget any assumptions you have on how/why things work on acvws. They DON'T work the same way as 75% of "other" engines.
The 34PICT-3 had a few variations over the years to match different distributors. If you have a "new" one it is probably an aftermarket one. If so, take it apart and clean it and blow out all passages. Many are known to come from the factory with dirt/dust in the passages.
Also, it may not be an ideal match to your distributor. The jets and throttle plate holes may be different than your original carb.
The Dual Vacuum Dual Advance (DVDA) distributor are the later emission distributors. They had a vacuum retard (yes, retard) that activated at idle and the vacuum advance did nothing at idle. Once the throttle opened just a little the vacuum retard lost vacuum causing the distributor to advance as soon as the throttle opened. Also, the vacuum advance port in the venturi was exposed on throttle open and created more advance. Mechanical advance added more advance as the rpms rose.
This may be different than other distributors you may have worked on.
It's emissions control as much as it is driveability. The vacuum advance and retard ensures a positive increase in rpm off idle without using an extra shot of gas, and ensures a positive decrease in rpm without choking the engine out and milking a bunch of gas out of the carbs.
Wave of the future baby! |
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| bluemagman |
Fri Nov 20, 2009 5:54 pm |
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| I looked my distributor and none of the numbers are in the orange manual. I have about 20 degrees total mechanical advance and almost 40 degrees with the vacuum connected. I have the timing set at 0 degrees, it won't run with 5 degrees retard. I tried to set the fuel mix and the idle. The idle screw does almost nothing and the mix screw is out 20 turns. |
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| Randy in Maine |
Sat Nov 21, 2009 5:25 am |
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Suggestion:
Go here and look up the distributor number and time the engine accordingly.
http://www.oldvolkshome.com/ovhignbo.htm |
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