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Old 28-03-2006   #1
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Vacum advance

Hi Guys
I checked my vacum advance last night and found there was no resistance to me sucking or blowing.
The car runs fine and ticks over nicely.
What are the downsides to having a leaking unit?
I am hoping to get another uno for spares and so will transplant this unit soon.
Cheers
Pete
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Old 28-03-2006   #2
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Re: Vacum advance

Quote Originally Posted by Peterg
Hi Guys
I checked my vacum advance last night and found there was no resistance to me sucking or blowing.
The car runs fine and ticks over nicely.
What are the downsides to having a leaking unit?
I am hoping to get another uno for spares and so will transplant this unit soon.
Cheers
Pete
Hi Pete,

A failed vacuum advance will make the engine run on the weak side, as with no resistance from the vacuum unit the carburetor will draw extra air in from the connecting pipe. More air = weaker mixture.

Normal symtoms for a failed unit are poor tickover, stalling and hesitation when accelerating. Your distributer also won't be giving the correct advance/ retard settings for the ignition.

If you've got access to a timing light, check the timing. If the timing is set correctly (vacuum advance pipe disconnected and plugged), the engine will tick over roughly. Once the pipe is reconnected, the correct advance/ retard settings come into play and the engine will tick over much more smoothly.

It is possible to get the engine to tickover ok with a failed vacuum unit, but the only way to do this is to adjust the distributer until it runs smoothly. This is ok at tickover, but the ignition settings will be out as soon as you rev the engine.

They're not expensive, so for peace of mind fit a new one, or one from your spares car
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Old 28-03-2006   #3
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Re: Vacum advance

I think they cost about 10 from shop4parts
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Old 28-03-2006   #4
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Re: Vacum advance

Thanks for that pal, do u know if I can swap one from a 93 1.0 ie or do they have different settings?
Pete
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Old 29-03-2006   #5
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Re: Vacum advance

Can anyone tell me how much resistance the unit should give and is it while sucking and blowing?
Thanks
Pete
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Old 29-03-2006   #6
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Re: Vacum advance

Quote Originally Posted by Peterg
Can anyone tell me how much resistance the unit should give and is it while sucking and blowing?
Thanks
Pete
- almost full resistance on sucking
- very small resistance on blowing
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Old 29-03-2006   #7
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Re: Vacum advance

Thanks.
I had ago today swapping over the unit and could not see how the plastic shaft that extends from the unit into the dizzy releases.
Any advice appreciated.
Pete
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Old 29-03-2006   #8
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Re: Vacum advance

Just done this job tonight, i managed to snap the plastic arm off when removing my old unit, then i had to fish out the other bit. I did this by sticking a large screw-driver in and forcing it but then that broke it so perhaps not the best method but it works !

Took ages to get it to fit, until i made the hole on the plastic end slightly larger with a 4mm drill and it slotted in fine and works a treat
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Old 30-03-2006   #9
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Re: Vacum advance

Yes your right had ago myself but found that the plastic shaft looked like it was about to snap so I held back, I may try and swap a whole unit including the dizzy if I get hold of one.
P
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Old 31-03-2006   #10
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Re: Vacum advance

Yeah, you push a screwdriver into the slot until it releases. I haven't had one snap yet - it's made of super-plastic

Putting the new one on can be a little fiddly, but a screwdriver pushed into the slot (again) and maybe twisted a little, and another screwdriver prying upwards, and it should pop on fairly easily. I wouldn't enlarge the hole personally, I think it's good if it doesn't come off too easily...

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Old 31-03-2006   #11
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Re: Vacum advance

Thanks Alex
Knew you would have invaluable experience of this task.
Pete
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