Club 80-90 Forums

Hi,

I'm working on a 2.0l a/c engine with Solex PDSIT34 carbs.
Whilst running at idle there is a vacuum signal from the hose that connects to the distributor retard but dis/connecting makes zero difference on the timing. I'm fairly sure the distributor is good as a manual suck on the pipe moves the baseplate and it was working previously. All vacuum pipes/rubber elbows on central idling circuit are sound. The vacuum is perhaps a bit weak so my question is: Is there a correct value for the vacuum and can I measure with a gauge of some sort?

The source of the problem could be the that throttle valve basic setting is incorrect (although I've carefully followed Haynes to <0.1mm open from closed). A photo of the left hand carb throttle valve attached. Does anyone know if the hole marked in the photo should be completely covered (to create better vacuum?) or does this look right?
Am I missing something altogether perhaps
Any thoughts appreciated

Hello,

If you can pass a 0.8 mm mig welding wire between the butterfly and the venturi, with the carb in the fully warmed up idle position,
and the choke step cam is completely off the step, then you should be good...

As for the vacuum signal, it should read about 5 mm hg of depression, at about 800prm, distributor disconnected..

To see the gauges, this may help:

https://www.youtube.com/watch?v=4qayyc9Z4E0&t=3s" onclick="window.open(this.href);return false;

and then..

https://www.youtube.com/watch?v=dsfo5ATgBp0" onclick="window.open(this.href);return false;

Air-Cooled Bliss...

Cordialement,

Hi Sarran and thanks for the videos (as always!)

With a warm engine and the chokes completely off the cams then I was working to <0.1mm (as per Haynes). Isn't the 0.8mm spec for when on the fast idle cams?

I'm going to source one of those vacuum gauges so I can get a better idea of vacuum condition.

matteo wrote: Isn't the 0.8mm spec for when on the fast idle cams?

Yes, and it is should be 0.65mm.

Bypass the hose that goes to the air filter and check again, sometimes the thermostat or the preheat diaphragm can leak and suck in air.
You are better getting a vac pump. You can use it for checking vacuum and creating vacuum and checking for air leaks or working the vac advance retard.

https://www.ebay.co.uk/itm/Hand-Vacuum- ... Sw5UZZAEp2" onclick="window.open(this.href);return false;

Thanks for the suggestion, I tried that to eliminate a potential leak but no difference.

I continued by closing the throttle basic adjustment (ie warm and off choke) right down towards fully closed and hey presto the retard started working as expected!
I think the advance was coming into play at idle to counteract the retard signal.