Aircooled VW South Africa

Hi guys and girls,

I got my type 4 (1700) twin carb project car started but it won't idle.

It revs up very nicely and sounds strong. Also doesn't smoke and starts easily. I wanted to avoid stripping the carbs in fear that I might struggle to find service kits etc.

I noticed that the idle solenoid's tip is cut off and assume it was done because it doesn't work any more (does not activate with power applied)

Is there any obvious checks I could do before stripping down the carbs and starting at 0 base?

Thanks!

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Which type of idle solenoid does it have? Carbs on 412 have a fuel cutoff solenoid on each carb. This is part of the idle/progression fuel jet. Make sure this jet is not blocked.
Kombi carbs have an additional, much bigger, central idle mixture cutoff valve on left carb.

Dawie wrote:Which type of idle solenoid does it have? Carbs on 412 have a fuel cutoff solenoid on each carb. This is part of the idle/progression fuel jet. Make sure this jet is not blocked.
Kombi carbs have an additional, much bigger, central idle mixture cutoff valve on left carb.

Hi Dawie, this is what my set up looks like. There are 3 points that invite electrical connections. If I'm not mistaken the far left tubular unit is the idle cut off solenoid?

I'm not sure what the others are for, but I do not have power connected to them.

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mhsmuts wrote:

Dawie wrote:Which type of idle solenoid does it have? Carbs on 412 have a fuel cutoff solenoid on each carb. This is part of the idle/progression fuel jet. Make sure this jet is not blocked.
Kombi carbs have an additional, much bigger, central idle mixture cutoff valve on left carb.

Hi Dawie, this is what my set up looks like. There are 3 points that invite electrical connections. If I'm not mistaken the far left tubular unit is the idle cut off solenoid?

I'm not sure what the others are for, but I do not have power connected to them.

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On closer inspection I now see that the smaller tube solenoid looks missing on mine...

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Those are kombi carbs.
On that one, the fuel cutoff valve was replaced with a fixed idle jet. It's the brass thingy below the parting line, (hexagon nut of 8mm with groove for screwdriver). Make sure its not blocked.

Great, Ill do that.

Just 2 questions please Dawie:
(1) Is the larger left hand solenoid valve bypassed with plunger tip cut off, i.e. cannot be the cause or at least be contributing to it? I.e. should I replace it?
(2) should I apply power to the terminal on the rectangular part between the two solenoids? what is this for?

Thanks again,

Morne'

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1) Cut-off plunger tip should not prevent engine from running.
2) Rectangular box is enrichment for central idle system of kombi-type carbs.
3) That tall pipe on top of left carb...is it connected to the balance tube?
4) Idle speed is adjusted by turning that large screw on top next to the tall tube.

mhsmuts wrote: Wed May 22, 2019 6:17 pm Hi guys and girls,

I got my type 4 (1700) twin carb project car started ...

Great going!! I'm sure you're glad that you dumped the single-carb idea. You're on the right track and soon all your efforts will be rewarded.

Dawie wrote:1) Cut-off plunger tip should not prevent engine from running.
2) Rectangular box is enrichment for central idle system of kombi-type carbs.
3) That tall pipe on top of left carb...is it connected to the balance tube?
4) Idle speed is adjusted by turning that large screw on top next to the tall tube.

(1) ok tx
(2) should I put power onto it? Would it affect the idling?
(3) it is not no, should I connect onto the tube that connects to the two nipples on the manifolds?

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73type2 wrote:

mhsmuts wrote: Wed May 22, 2019 6:17 pm Hi guys and girls,

I got my type 4 (1700) twin carb project car started ...

Great going!! I'm sure you're glad that you dumped the single-carb idea. You're on the right track and soon all your efforts will be rewarded.

Thanks! It was a big moment yes!

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That bigger solenoid / plunger at the back of the carb which controls the central idling must have ignition power to it. That will effect your idling if its not connected, BUT, quite often the plunger inside will have been cut off and connecting the power to it will have no effect then. You can unscrew it and check for the plunger connected to it.

As Dawie also mentioned, your idle jets on both carbs could be blocked.

There is very little consumables on these carbs. 99% do not understand them and focus on the incorrect methods. Its taken me about 20 years to fully understand, rebuild and set them up properly.

Don't forget other possibilities such as vacuum leaks that will also cause idling issues.

sean wrote:That bigger solenoid / plunger at the back of the carb which controls the central idling must have ignition power to it. That will effect your idling if its not connected, BUT, quite often the plunger inside will have been cut off and connecting the power to it will have no effect then. You can unscrew it and check for the plunger connected to it.

As Dawie also mentioned, your idle jets on both carbs could be blocked.

There is very little consumables on these carbs. 99% do not understand them and focus on the incorrect methods. Its taken me about 20 years to fully understand, rebuild and set them up properly.

Don't forget other possibilities such as vacuum leaks that will also cause idling issues.

Thanks Sean. Do you perhaps know where I can get ahold of a schematic of the carbs showing which set screws and jets are for which specific purpose? Would safe me from asking stupid questions here...

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Seems that your carbs are from a different 1800 or 2l kombi engine. Those brass/copper thermostats for accelerator pump volume (behind float bowl), were introduced somewhere around the 1975 production year. The ones which lives next to the drain plugs.

Best to always do fault finding first. Only do carb adjustment once you are sure that is the problem. Otherwise some new faults gets introduced. Valve clearances always needs checking before adjusting carbs.
The Haynes manual for the 411/412 would be of good help.

Some pictures stolen from the net:




Beware that most of the adjustment procedures from American forums does not apply. American market models have emission control devices, like exhaust gas recirculation, vacuum retard at idle, air injection pumps, etc.
Also timing settings and jetting differ.

You see thats why its so good to have members that have a wealth of knowledge and is appreciated by those of us who are not so familiar with these vehicles and this helps to newer aircooled guys to have the support to get them involved in jobs they would have never attempted before. Thanks guys good to have you on board that goes out to all you who contribute to this forums survival.

Thanks Dawie, the puzzle pieces are slowly coming together.

My biggest challenge is the fact that the car is no where near what it was when it rolled off the production line. From what I can confirm, it was a fuel injection model at some stage, which explains the odd model carbs on it.

I am missing a few parts when looking at the central idling circuit:
1) the pre-heater
2) thermo valve

Am I correct in thinking that the brass vertical upright tube on the left carburettor connects to the air filter housing, i.e. just needs clean air?

The horizontal brass tube opposite to the central cut off valve - should this also just be connected to a filtered air supply?

Should the nipple on the two carburettor manifolds (as per my previous post) simply be connected with a rubber hose?

Thanks again for all the help everybody.