TheSamba.com :: View topic

Tue May 02, 2023 9:23 pm

I have a dreaded single Weber on my type 4 engine. I have been fighting it for years and always seem to bring it back into working order. But, it continues present me with 'opportunities' to learn.

The latest issue seems to be associated with the choke - On start up, it idles too fast and doesn't respond to when I step on the accelerator in an attempt to 'step it down' to lower RPM's. Other symptoms include poorer gas milage, hesitation after a stop, and a dead spot if I open the throttle up all the way (flooring it). It used to be that when I applied the accelerator pedal, I would experience a steady increase in power and speed. But now I don't get this immediate response. (Of course, I realize it's a VW engine so I'm not expecting 0 - 60 in 15 seconds) but smooth acceleration is not always achieved with the throttle open all the way - like when getting on the freeway and wanted to get up to 55/60 MPH.

What adjustments might I consider to my carb and the choke?

Thank You,

Jeff

Tue May 02, 2023 10:33 pm

read the Holley book, Bentley etc to learn how it is supposed to operate, or find someone near you who knows progressive carbs. It isn't something that is easily explained to anyone via the Internet. The carb has to be tuned to run correctly at idle and RPM when warm, then adjusted cold, then the fast idle cam adjusted to the proper speed and steps. The distributor needs to properly advance and drop back smoothly as well. There are many steps including rebuilding it to spec with the proper parts. Whaang, there just isn't going to be an easy answer. It can be done but there is some studying involved.

Wed May 03, 2023 12:43 am

It will not release the fast idle until the choke has warmed up and allowed the stepped cam buried behind the choke heater capsule to rotate.
The PTC ceramic heater element in my choke heater was all smashed up so I was driving round with the choke on all the time. Not good for economy, but once the engine speeds up the choke vacuum pull off should cancel the choke.
Worth checking there is a DC resistance from the choke heater tag to ground on the carburettor.

Wed May 03, 2023 5:11 am

Was it running well with the current settings, and now it's not? If so, it may not be "out of adjustment", really.

I've got a 32/36 weber on my Jeep 258, on my MG, and on my Bus. I know some people hate them, but I've had good luck with the carbs for years.

When I've had choke problems, I've found that it's often a binding / lubrication issue in the choke linkage. The coiled spring doesn't really exert a whole lot of force to move the choke plate, and if the vehicle has been sitting - like over the winter - if the linkage is dry, it can resist movement. Make sure the linkage is free and lubricated.

My two cents.
Good luck
Hobo.

Wed May 03, 2023 2:01 pm

Thanks for your comments.

The issue here is that was running very well prior to being put away from the winter. (with lots of TLC over the years including a complete rebuild, new jets, needle valve(s), floats, etc).

When I got it out in early April, it also was running very well. But after a couple of weeks, I started noticing small signals of it running more poorly. I think the thing that caught my attention was the fact that I can't get it to 'kick down' into a low idle speed like it used to do.

NOW - there is one variable that I failed to mention and that is we've had a lot of rain and cold weather here in Rochester over the last couple of weeks. Perhaps this is a factor?

Wed May 03, 2023 2:12 pm

just do three things for now.

(1) verify that the choke is opening when the engine gets warm. Maybe the element has a wire that fell off, or it has burned out. The choke butterfly could be sticking and need some carb cleaner sprayed on it to make sure it moves freely.

(2) Make sure the distributor advance is properly moving. A little stickiness there will hold the advance up and that will make it run fast at idle and poorly. Some drops of oil on the distributor wick under the rotor and a little on the breaker plate is a normal annual service.

(3) make sure no vacuum hose has come free. A vacuum leak can make it run fast at idle.

Wed May 03, 2023 5:07 pm

Whaanga wrote: NOW - there is one variable that I failed to mention and that is we've had a lot of rain and cold weather here in Rochester over the last couple of weeks. Perhaps this is a factor?

The second variable is a lack of lubrication under the distributor rotor… :wink:

High idle can be caused by sticking mechanical advance. Wacky acceleration can be caused by sticking mechanical advance. Poor fuel economy can be caused by sticking mechanical advance. (In the words of Adam Neely, repetition legitimizes, right? :lol: )

A sticky or over-adjusted choke can cause those symptoms too. Easy way to rule it out:

- mark the choke position where it is now so you can get close if you need to backtrack
- on a cold engine, loosen the choke adjustment and spin the choke element until the flap holds vertical
- snug choke adjustment

This should take care of the choke adjustment (air blocking flap sensitivity,) and fast idle adjustment, which operates off the choke mechanism. Then you can enjoy a test drive and see if you really want that "biggest item of built-in obsolescence" according to John Muir…

Robbie

Fri May 05, 2023 2:53 am

5 minutes after startup the choke should be all the way open. If not figure out why. If it is open make sure the fast idle cam has returned to the hot position, there is not much force to cause this to happen, so it doesn't take much friction in the system to make it fail to return.