Re: Vacuum retard unit

[Tom Jell <thomas.jell@domain.elided>]

Alexander

>    I have a question regarding the Vacuum retard unit on the distributor. I

Hmmm, I'm not that sure about US models, but our Stags have a vacuum advance unit.

>think that the diaphragm is bust. To test it, I took the other end of the
>hose coming out from it and tried to suck on to it and then plugged it. I

I bought a new one from Rimmers during my engine rebuild. Sucking didn't do any effect on the new one as well (maybe I need some more exercising ...)
Anyhow an hand air pump did prove the malfunction of the old one.
The new one had two connectors, I assume to use it for advance/retard on different cars. So sucking on one side is the same as blowing in on the other.

>removed the cap and looked for movement, and also waited to see if the unit
>held vacuum. Would this seem to be a good test on the device?

Additional you can block the pipes and try to push the lever. If it moves or/and you hear air blowing go for a new one.

>Could you also suggest hoe much of a difference this unit makes on the
>running of the engine, cos I am lost to its purpose.

In the ROM there is a detailed table how much advance you get depending on the pressure. On idle there is not much vacuum so it's only arround 2 degrees advance, but notable with an ignition time flasher.

Additional you can try to connect a test pipe/tube from the inlet manifold where usually the air input control valve is connected. There is a significant vacuum (like for the power steering). This will give you significant advance when things are ok.

If you need the exact advance details from the ROM, just let me know.

Tom