Running when Cold (or Not running well)

[Ryan P]

Running engine when cold. On a cold morning the Bus will always fire right up but the issue is when I try to drive. All cylinders will do not fire. I will always let it sit idle and warm up for about 5 minutes sometimes a little longer. This helps but for the first 1 mile of driving it will not have any power. It has a single progressive carb. I am guessing the issue is with the cold manifold pipes?

The second question may be a related issue, I think I had a little fuel in the oil. I checked the oil before heading off to work and the oil level was right at the full line. I did not let it warm up as much as I normally would and had a much hard time getting the Bus to move. I had to really feather the clutch while bringing the RMPs up. In this process this process as stated above guessing the Bus is misfiring. This misfiring issues is with starting then again from 1st to 2nd and 2nd to 3rd. The bus is real sluggish until the RMPs get a little higher. After retruning home for the evening 70 mile day chacked the oil again and it was about 1/8” higher on the stick. Could the misfiring of the cold morning mix fuel with the oil this much?

The carburetor was rebuilt last Fall because of fuel getting in the oil. It had a bad float.
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1969 Beetle
1972 Camper
1977 Beetle (Standard)

[Wildthings]

Have you pulled the air cleaner off and watched the actions of the choke butterfly? Once you set the choke on a cold engine by doing a full pump of the throttle pedal, then the choke should close fully. Immediately as the engine starts it should open so there is about an 1/8" gap betwen the butterfly and the walls of the carb throat and then over the next three to five minutes or so the butterfly should fully open. It is usually better to have a bit too little choke verse too much, though you may see a power loss if you give the engine a lot of throttle too quickly.

Too little choke and the engine will sputter and die as you give it throttle, and too much it will have poor power, load the engine oil and exhaust with gas, and maybe die as well. You can see if you need more or less choke by moving the butterfly with your fingers and then seeing if the engine revs smoothly.

It is normal that the first time you try and move the vehicle after a cold start that you may have to pump the throttle a few times as you move off.

To get heat to the carb, the cookie tin idea is quick and easy, especially if you have the intake air preheat parts for a 72-74 engine available.

If the carb is mounted so the choke coil is facing the rear of the vehicl, adjusting the the coil is not big deal, but if the choke coil is facing forward you need to use braille and it is hard to know how much you have moved the coil, even though a tiny movement of the coil makes a big difference in how fast it opens. Paint marks you can see in a mirror would help here.

[Ryan P]

Thank you for the information. It looks to be set the way you describe. Here are a couple of pictures one after just starting and the other after a few minutes. Video link of the start up https://photos.app.goo.gl/q2k543tigJ8hY2Fb8

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1969 Beetle
1972 Camper
1977 Beetle (Standard)

[Wildthings]

If you are letting your engine run for 5 minutes before driving off, maybe you are getting carburetor icing occurring and it just won't run well until the engine warms enough for the icing to dissipate.

I usually only allow my engine to run for a minute or so after a cold start before I drive off and not long afterwards with the engine being forced to work, the heads are dumping enough heat into my intake air preheat system that icing can not occur.

Note that when trying to move the choke butterfly by hand, to get the choke to close you need to simultaneously open the throttle a bit.

[aeromech]

An eighth of an inch might just be the warm oil expanding. Check it again when cold.

As said, these carbs are real bad for icing. As the engine is warming up, you intake runners are getting colder and colder. After 5 minutes they are so cold that the fuel isn’t much of a vapor any more and you’ll get poor throttle response. Try starting up and just go. I bet it runs better for the first few miles. Still, you’re fighting an uphill battle trying to make your engine run good with that carb.
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[Wildthings]

Does your thermostat system work properly? A properly operating thermostat is important in the cooler months to get the engine to warm up quickly and stay warm.

[Ryan P]

When I rebuilt the carb last year there was a hole in the bottom of the air filter plate that did not have any connection to it. Could this have been a way to get warm air to the carb(crankcase vent hose was on top)?

[Ryan P]

[mikedjames]

[Ryan P]

Sorry, I should have said the picture of the carb is from before I rebuilt it. I have the red-circled items taken care of. I grab the picture from an old post of mine. The question is what do you think the PO had connected to the port coming out of the bottom of the air filter plate. He had the Crankcase hose on the top.
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1969 Beetle
1972 Camper
1977 Beetle (Standard)

[Wildthings]

What distributor do you have and waht do you have your engine timed to? In the winter you can time it to 32° BTDC @3800+ rpm, hoses removed and plugged, to give your engine a bit more pep when cold. During the summer its best to run closer to 28°.

[Ryan P]

[Ryan P]

[jaket3]

Fundamentally I think your issue is the single carb.

It's not the ideal solution on that engine as there is no preheat on the manifolds. As mentioned it causes carb icing.

A couple of things:
The breather box has a hose coming out of it. This should feed into the air cleaner. Where does that hose go at present?

Choke
Certainly go through the tune up procedure for that. Maybe it's not coming on when it should.

Themostat.
I don't think this is related to your issue. But you should get it installed as it will help the engine come to temp quicker which is better. It may marginally help the carb icing issue. But won't be a magic bullet.

If you can I'd look to putting dual carbs on there. They have short manifolds that will warm quicker and you won't have the icing issues. It doesn't have to be cold to have these issues. It's cold and / or humidity I think.

I just made this change on my bus and it runs a lot better. Plus a bit of extra power.

[Ryan P]

[Wildthings]

The question with the distributor is is it an 009 style mechanical only distributor or is it a SVDA (single vacuum, dual advance) that has both a mechanical advance and a vacuum advance. It could also be a DVDA (dual vacuum, dual advance) distributor which has a vacuum can with both an advance and retard function, but I have never seen an electronic version of such, though an electronic pickup can be added to any one of the above.

Search the forum for the cookie tin preheat idea and in the long run either disable the power valve and rejet, or modify the power valve's function to get more fuel as you first open the throttle. These carbs can be made to run very well, but out of the box they have problems.