TheSamba.com :: View topic - Dual Solex PDSIT

Wed Aug 08, 2007 8:20 pm

All,

I've been getting my dual carbs set up and ready to install using Bentley, Colin's procedure and Ratwell's site.

I understand the vacuum ports on the left carb (both advance and retard), but haven't come across any pictures or documentation about what to do with the single vacuum connection on the RIGHT carb. Should this just be blocked or should it be connected to something?

For the record, I've got the 73-74 setup (as pictured in Colin's procedure) with EGR deleted.

Any thoughts?

Thanks,

Scott

Wed Aug 08, 2007 9:20 pm

The vacuum port on the right carb went to a switch that affected vacuum to the dizzy in 4th gear only. The switch is atill in my '73 bus, but I have never hooked it up. Colin simply put a piece of vacuum hose on the nipple and plugged it with a screw. There is no need to use this nipple fitting.
Best Regards,
John

Thu Aug 09, 2007 5:34 am

Soulful,

Interesting. I had thought, based on this photo:

http://www.ratwell.com/technical/VacuumHosesCarb/VacAdvCutoff.jpg

...that this advance switch was driven by the left carb advance port, with the vacuum hose downstream of this switch connecting to the vacuum can on the distributor.

Thu Aug 09, 2007 5:54 am

I thought that as well, I believe the RH fitting is for the EGR or the aircleaner preheat.

Thu Aug 09, 2007 5:59 am

is that for an automatic tranny? my manual doesnt have that vacuum can...... another piece i am missing?

dave

Thu Aug 09, 2007 6:37 am

vttype2,

Ratwell's site has information on the vacuum switch - it turns on /off the vacuum advance in 4th gear - he has a much better explanation of it. I don't plan on hooking mine up.

Busdaddy,

Looking at Ratwell's pics, it appears the preheat valve is controlled by a line from a tee off the brake booter elbow on the RH side.

Thu Aug 09, 2007 10:36 am

my 73 automatic doesn't have that piece either.

hmmmm

Thu Aug 09, 2007 7:37 pm

I stand corrected. Thanks for the link, and getting the correct info on this!! Sorry for the erronous info...looks like you are on your own to research this. Best of luck!!!!
Best Regards,
John

Thu Aug 09, 2007 8:21 pm

The Bentley (Section 5 - Engine and Clutch - 19.2 Distributor) states that this vacuum can is on all dual-carb models except for 1974 models with manual transmissions and disables vacuum advance when the temp is above 54F for all gears except 4th.

This would seem to indicate that it is on automatics too.

However, in the testing section, step 3 starts with "Have someone depress the clutch pedal..."

So, I think we can logically conclude that this device is not present on automatic dual-carb busses.

Thu Oct 11, 2007 7:41 am

Out of interest was there any resolution to this thread as I have exactly the same problem and don't have any ideas what to do: :roll:

http://www.volkszone.co.uk/VZi/showthread.php?t=395794

Cheers
Juliette

Thu Oct 11, 2007 8:44 am

It's for early EGR.

Thu Oct 11, 2007 8:45 am

Sorry, what's EGR. And does that mean you know where my pipe goes :) ?

Thu Oct 11, 2007 9:02 am

Exhaust Gas Recirculation - basically an emissions control system

More info here --> http://en.wikipedia.org/wiki/Egr

I resolved the issue by adding a short length of hose to the fitting and putting a screw in the end.

Thu Oct 11, 2007 9:35 am

Thanks for that

So I am guessing that it does not go to the fuel breather system then??

Thu Oct 11, 2007 10:32 am

This is year and model dependent, and may have been modified.

The stock US 74 right carb port gives vaccum to the EGR valve;
The left carb port and throttle flange give vaccum to the advance and retard distributor can.
The 4 legs tube assembly has a nipple at the center valve giving vaccum to the smog pump's primary stage valve and the thermoswitch in the air filter right horn.

I found my two carb ports, vaccum hoses were switched ( from PO or mechanic ? ).

Because of various EGR set ups, there are more vaccum hose variants.

Thu Oct 11, 2007 11:19 am

Fuel breather or vapour (vapor) system all goes to the charcoal canister, which goes into the air cleaner. later FI versions include a vacuum valve on the air cleaner to prevent fume loss when parked.

Fri Oct 12, 2007 12:38 pm

I have a 1972 1800. It has spent it's life in Australia only coming over to the UK in 2005, when I bought it.

The van has no EGR, no Chracoal cannister, I only have advance on the distributor and No retard.

I am only asking because when I disassembled all of this I was a LOT more naive about VW's than I am now and it didn't occur to me to see where every vacuum pipe went as I thought it would be self explanitory on reassembly - how wrong was I !!!!!!

So I am left with this pipe that I have no idea where it goes

The pipe that is attached obviously went to somewhere and I can only guess that this was the fuel breather system - maybe I'm wrong :?

Fri Oct 12, 2007 2:45 pm

Juliette wrote: I have a 1972 1800. It has spent it's life in Australia only coming over to the UK in 2005, when I bought it.

The van has no EGR, no Chracoal cannister, I only have advance on the distributor and No retard.

I am only asking because when I disassembled all of this I was a LOT more naive about VW's than I am now and it didn't occur to me to see where every vacuum pipe went as I thought it would be self explanitory on reassembly - how wrong was I !!!!!!

So I am left with this pipe that I have no idea where it goes

The pipe that is attached obviously went to somewhere and I can only guess that this was the fuel breather system - maybe I'm wrong :?

I assume you have a nipple/port and hose just like this on the left hand carb that is hooked in to your distributor vacuum advance can, correct?

If that is so, you have two options:

1) Tee this hose in to the hose between the left carb and distrubutor vacuum advance, since it sends a similar vacuum signal at partial throttle or;

2) Plug off the nipple/port with a rubber cap or a short piece of hose with a screw in the end, just like was described in the posts above. You don't need more than one carb to supply the vacuum signal to the distributor to operate correctly.

Don't hook any carb vacuum hoses to the fuel evaporative or crankcase vapor recovery system, please.

Good luck, Tim

Fri Oct 12, 2007 6:00 pm

Just WTF is that brass thing sticking out of the bottom side of the float bowl to the right of the accelerator pump? Some kind of temp. or altitude compensator? Never seen that before, some kind of crazy Aussie stuff?.

Fri Oct 12, 2007 6:43 pm

That brass thing is the thermostatic valve - apparently used to regulate the quantity of fuel injected by the acc. pump. and only on 1974 automatics.

See the Bentley - Fuel System section Figure 5-23