Cold weather hesitation

So, my van hates the cold. It starts up nice and brightly, but if I don’t give a wee bit of throttle, it will idle low and die. Until it’s warm, taking off in first requires high revs or it stalls. Once it’s properly warmed up, it’s fine.

I’ve established the following:

1) The vacuum advance is (was) not hooked up.
2) The vacuum hose for the air cleaner pre-heat valve is not hooked up.
3) The vacuum unit on the air cleaner (the sardine tin that hangs under the top intake) is missing.
4) The choke works but is not closing far enough when it’s cold.

(1) was easy, and I have now installed the hose, although I’ve yet to test drive to see if it makes any difference.
(2) is trickier, since some DPO has removed and sealed up the vacuum take-off on the manifold.
(3) is super-tricky unless I can get a new vac unit or maybe a whole new cleaner . Also, my understanding is that the top intake on the air cleaner is the cold air intake, and it is, rather oddly, permanently closed (I think, I certainly can’t push it open by hand). I can’t find much about the specific operation of this era of air cooler online or in the books. If anyone has a schematic, that would be super-handy.
Finally, (4) I can adjust myself—I’m guessing this is most of the idle problem, since the fast idle cam is the same mechanism as the choke (right?). I’m trying to do things one at a time to isolate the effects, so I’ll wait until I see what the vac adv changes first.

Am I right in thinking these things are likely causes of the cold idling/hesitation problems? Is there a good reason anyone would do this to an otherwise stock Typ 1 engine?

 

Sounds like you're going in the right direction. After a dab on the throttle (to release the choke/fast idle cam) a Bay should fire straight up and pull away nicely. Get your choke so that it releases nicely and shuts the choke flap and that the throttle stop is on the steps of the fast idle cam. Also that when the engine warms up, the choke opens fully. You may need to adjust the idle speed on the carb with the big screw - don't adjust it using the throttle stop.

Having the warm air feed working properly will certainly help in colder weather - have a look on eBay for used units.

 

PS When you're not using them, you need to cap off all vacuum outlets on the carb or manifold. Bunging up the vac can on the dissy won't do anything

 

I connected the vac unit on the distributor to the carb just above the throttle valve with vacuum hose. Unless the vac unit is buggered, it should improve my flat spot, right?

 

It should.

 

Also, the vacuum hose fitting that’s normally on the manifold has been removed and the hole blocked up permanently. Is it worth reinstalling that fitting, or can the vacuum be taken off the carb? I’m guessing not, as the carb only has vacuum when the throttle is open, and the fan pulls air continuously.

Moot until I can source a replacement air cooler, though.

 

VW took manifold vacuum from two places over the years: from a small pipe on the manifold, or from a connection right at the rear of the carb, pointing straight at you (later vans/carbs). Either will do to power the warm air flap.

 

Thanks!

 

Easy enough to take the manifold off and redo the connection with a barbed fitting.

 

At some point you would need to take off the air cleaner from the top of the carb so you can see the choke plate opening and closing as it should. In your pic, you can see the choke housing behind and to the right of that propeller shape. the choke unit should have a wire to it for the heating element and the round choke housing has 3 screws which can be loosened and the adjuster ring turned ever so slightly to set the choke action.

Setting the choke correctly will have a big effect on your cold starting and settling down to idle without stalling.

 

Yeah, I pulled the air cleaner hose off the top of the carb today and took a look. Not easy to see (jealous of all you later bay types with your access hatches), but it was about halfway open today, air temp around 7°C. I took pics, since that was the only way I could actually see it.



Ran it for a bit to get warmed up and then checked and the butterfly was all the way open. I’ll adjust it next time I have a chance.

 

Actually, if anyone happens to know where their choke valve sits at today’s temp, I’d like to hear.

 

You are doing well. With the engine cold, could you do as @snotty says, dab the throttle and take a pic of the choke plate to see its closed position, By the way do you see ice on the outside of your carb, before it warms up.

 

That pic was post-throttle dab, so I guess that’s as closed as it gets, at least in this weather. I haven’t seen ice on the carb yet, but it’s not been cold enough lately.

 

Am I correct in thinking that the fast idle cam prevents the choke closing until you press the the throttle all the way down? When the throttle is opened, the stepped cam is released, and the bimetal spring is able to pop the choke valve closed, (and keep the fast idle in place)?

 

http://www.vw-resource.com/automatic_choke.html Try rob and daves their write ups ar3 straight forward to follow and a good to go on type 1 engines ,link added but theirs lots to read . It’s easier to understand sometimes . Good luck with it your see lots of little tricks with setting your throttle etc and where your carb “flap” should be when cold and once warmed up and setting carb too, always better to run a tad rich than toooo lean too .

 

Yes

 

Adjusted the auto choke today. When I first attempted to adjust it, rotating the body did not move the butterfly valve, so I think perhaps it had been installed badly previously. I took it off and made sure the spring was properly hooked on, tuned it to the top notch on the housing, and it worked perfectly. Lovely fast idle on starting, and a nice open choke once it warmed up .

Still having the problem with the engine stumbling when I dab the throttle, though. I’ll check the heat risers next time I take the van for a run, but I suspect it might be to do with the air cleaner.

I can’t find any schematics online, so if anyone knows the details of how this specific era of air cleaner (see photo at the top) works, I’d like to pick your brains.

 

Thanks for the tip!