Vacuum retard on distributer

Post by **davidwarren** » Sat May 05, 2007 9:24 pm

Hi, I wonder if you could help me with this one. I have a 1968 two door 1098cc moggie. When I remove the vacuum pipe from the engine manifold nothing happens to the rpm of the engine and if I suck the vacuum pipe with the other end still attached to the distributer, nothing happens. Does this mean the vacuum mechanism on the distributer is defective?
How can I rectify this problem? I hope my engine hasn't been damaged because of this.
Can anybody advise me on what to do please.

Many thanks, David, Washington, Tyne & Wear.

Post by **les** » Sat May 05, 2007 10:01 pm

Sounds like a faulty vacuum mechanism to me, when you suck on the pipe the lower plate in the distributor should move. You can buy the unit seperately.

Post by **Welung666** » Sat May 05, 2007 10:02 pm

I need one too

as Phoebe's doesn't work either, the diaphram is in about 5 pieces

Post by **davidwarren** » Sat May 05, 2007 10:30 pm

Thanks for your advise, I'll buy the necessary parts. Would my engine be damaged if this wasn't working?

Post by **davidwarren** » Sat May 05, 2007 10:32 pm

When I get it all working, how do I know how much to turn the micro adjuster thumbwheel?

Post by **les** » Sat May 05, 2007 10:42 pm

I would not think so, it may have run a bit hot as the advance was not working. Adjust the thumbwheel so as it's in the middle of its travel, set the points as normal, the thumbwheel gives fine adjustment.

Post by **Willie** » Sun May 06, 2007 11:05 am

The vacuum unit only comes in to play when there is no load on the engine i.e. when you are not asking the engine to 'pull'. The resulting vacuum causes the ignition timing to advance for greater efficiency. If
you fit a new unit the timing should be unaffected. You may find it necessary to slightly readjust the mixture but it will not be by much.

Post by **bmcecosse** » Sun May 06, 2007 8:51 pm

It's really just an economy device although when working it does 'brighten' the engine's response. They rarely last more than 10 years - sadly, not cheap!

Post by **wanderinstar** » Sun May 06, 2007 9:18 pm

Lee, I'm curious. How do you know the diaphragm is in 5 pieces?
The only way to tell this is to grind off the edge of the vacuum unit. I know cos I did it once to see what was inside. Were you curious like me?.

Post by **bmcecosse** » Mon May 07, 2007 7:13 am

I was wondering that too! Unless the case had fallen apart with rot?

Post by **Welung666** » Mon May 07, 2007 11:22 am

I'd opened it up, running without one now until I can get down to Luton to pick up a spare dizzy.

Post by **bmcecosse** » Mon May 07, 2007 3:03 pm

It's vacuum ADVANCE - not retard. Advances the ignition on closed throttle - ie high inlet vacuum.