Jump to content

Welcome to 205GTIDrivers.com
Register now to gain access to all of our features. Once registered and logged in, you will be able to create topics, post replies to existing threads, give reputation to your fellow members, get your own private messenger, post status updates, manage your profile and so much more. If you already have an account, login here - otherwise create an account for free today!


Tu3S Vacuum Advance

  • Please log in to reply
4 replies to this topic


  • Passengers
  • 24 posts
Joined: 11 Feb 2016
  • Name:Oliver
  • Location:Salisbury

My vacuum advance pipe dropped off the carb and the car now has much more top end and half the fuel economy, leading me to think that it wasn't working correctly to start with and the previous owner might have played with the timing to compensate.

I've tried sucking on the pipe and it makes no difference so I'm pretty sure at least the diaphragm is gone, if not the whole mechanism.

Anyone know where I can get a replacement?

And does it make much performance difference to run full advance and block off the carb?


  • Drivers
  • 122 posts
Joined: 10 Feb 2016
  • Name:Andrew
  • Location:Cockermouth Cumbria
Garage View Garage
It only works on over run and idle to retard the timing for fuel economy if say using twin carbs you would remove it any way it won't harm any thing but I would check the timing settings are correct as you may have to much advance if it was set up with it connected and working, I think it was meant to have the timming set with vacum off but not 100% on that as I never had mine connected and is pined inside my dizzy,


  • Drivers
  • 529 posts
Joined: 08 Nov 2009
  • Name:Dyl Roberts
  • Location:Anglesey
Garage View Garage

Funnily enough, I have literally just had the timing light on my TU3S to check the timing. The book says 8 degree advance with the vacuum advance disconnected. 

Edited by tdr_1976, 25 February 2016 - 07:19 PM.

Tom Fenton

Tom Fenton
  • Team Managers
  • 9,789 posts
Joined: 12 Dec 2007
  • Location:Rotherham South Yorkshire
Vac advance works at light throttle eg cruise. As soon as you floor it, the vacuum is gone and you are back to base timing. It helps economy a lot on cruise so it's worth getting it working really.

Mid-life 205

Mid-life 205
  • Passengers
  • 3 posts
Joined: 11 Dec 2016
  • Name:Alistair Brown
  • Location:Chelmsford, Essex
Garage View Garage

Sounds familiar. I just bought a Rallye with a mild cam and Webber. In diagnosing a flat spot I found the Vac was shot. To stop it sucking air and messing with the idle mix the previous owner had plugged the vac pipe and re-fitted it. :-) nice.


I took the distributor to these guys



Who repaired the Vac and spotted a broken bob weight spring at the same time.


Not big money and at least you know you still have the right distributor.

BTW I measured 11 degrees at idle when warm.