TheSamba.com :: View topic

Wed Feb 26, 2025 12:44 pm

How do you check to see if the Mixture Distributor (item #53) is working properly?

https://www.jerseylooker.com/FicheDump/EarlyBaywindow/1-068.jpg

Thanks in advance.

Wed Feb 26, 2025 2:11 pm

It's a pipe. It keeps the idle air/fuel mixture in, and the ambient air out.

If your engine runs well, you can spray it and all its junctions with carb cleaner at hot idle and listen for a speed change.

If your engine doesn't run well, use a rubber hose with a T in it to replace the pipe and things should change. Or you could pressurize one end and plug the other two, spray soapy water all over it, and look for bubbles.

In my experience, this part doesn't go bad. There are 5,268 other things to check before I would ever worry about this pipe. Can you describe the issues you're having? We can help better knowing the full picture.

Robbie

Wed Feb 26, 2025 2:25 pm

I will try your suggestions.

The main issue I am having with my stock 1.7L dual carb bus motor is that upon starting it stays on high idle until it reaches a certain temperature. Then it runs fine. The colder the day the longer it takes to idle at a normal level.

I have had the distributor and carbs rebuilt. Also, all vacuum hoses have been replaced. I have tried many times to try to get it to run properly and my VW mechanic has also been unsuccessful.

Thanks.

Wed Feb 26, 2025 2:33 pm

A higher idle when cold is normal, as long as it reverts to normal when warmed up it's working.

What kind of RPM are you getting?, it shouldn't get higher than ~1500.

Wed Feb 26, 2025 3:03 pm

That sounds pretty good! If the car idles normally when warm and drives smoothly, I would assume the pipe is fine. There is nothing more irritating than an engine that needs babysitting when started cold because it idles too low and wants to die…

The length of time AND cold idle speed are both adjustable when you've confirmed all the parts are accounted for and working, but getting some numbers like busdaddy said will be helpful.

The next thing I would check is the vacuum hoses to the distributor. If totally stock, you should have two. Removing vacuum retard hose (closer to the cap) when the engine is fully warmed up and idling normally should cause the idle speed to shoot up. If it doesn't, the vacuum can likely needs replacing, or the hoses are routed incorrectly.

Robbie

Wed Feb 26, 2025 9:36 pm

72vwtype2 wrote: I will try your suggestions.

The main issue I am having with my stock 1.7L dual carb bus motor is that upon starting it stays on high idle until it reaches a certain temperature. Then it runs fine. The colder the day the longer it takes to idle at a normal level.

I have had the distributor and carbs rebuilt.

Thanks.

Electric choke elements maybe need to be adjusted. Also the choke operating linkages on the carbs are very sensitive and might need to be adjusted. They might have been disturbed in the rebuild.

Start with the choke element adjustments, they are relatively easy compared to the choke operating linkages. On the stock dual carbs it's normal to have to adjust the choke elements several times to get them dialled in, since you get one or maybe two times per day to adjust them.

Thu Feb 27, 2025 6:29 am

for carb tuning
https://www.itinerant-air-cooled.com/viewtopic.php?t=7767

Thu Apr 03, 2025 5:46 am

Installing the thermostat and cooling flaps will also help immensely with cold starting. At start up the flaps are closed allowing the engine to warm up to normal operating temperature fast at which point the flaps open allowing cool air into the system and idle to drop.

Thu Apr 03, 2025 9:28 am

Excessive cold idling is not good on an engine, at temperatures about 20°F best to fire it up give it a short while (30 sec to a minute to warm) and then drive off, and if the temperatures are below that maybe give it another minute. If the air preheat is working well and heat is getting to the bottoms of the carb(s) normally then it should run smoothly pretty much from the get go.

Thu Apr 03, 2025 9:33 am

there is a specification in the manual (Bentley) that gives the fast idle speed. It is adjustable. Setting it is part of the tune up process, and it cannot be set properly off the vehicle so the shop that rebuilt the carbs could only estimate it for you. Same for the idle mixture. As to the choke, on my 1971 bus I had to have a summer and a winter setting on the choke for it to run just right, but I was being picky.