Advance and retard vacuum?

[R_Parr]

Hello,
I have taken my moggie to the garage because the engine 'cuts out' while driving, mostly randomly. I have rang them and they say i need an advance and retard vacuum? It changes the timing of the engine, or something similar.

They claim to know how to fit it but i don't have a bloomin clue what it is or where to buy one from.

Any help of what it is and where to buy one would be brilliant.

Thank You,
Rhys.

[PSL184]

I would doubt it - take it somewhere else for a second opinion if I were you ;-)

[mike.perry]

It is very unlikely to be the vacuum advance that is causing your engine to cut out. The vacuum advance would simply improve the acceleration, the engine would still run without it, just not so well. You can check it yourself by removing the little plastic pipe that runs from the distributor to the carburettor from the carburettor and unclipping the distributor cap. If you look inide the distributor you will see a metal plate with a spring attached. By sucking hard on the end of the plastic pipe you should be able to get the metal plate to move slightly and if you put your finger over the end of the pipe you should be able to feel the suction on the pipe.
If the vacuum unit is faulty it is easy enough to change, just time consuming and therefore expensive if you are paying labour costs, especially as it is not likely to be the problem.
The problem is more likely to be a faulty coil or condenser or even the fuel pump.

[rayofleamington]

The vacuum advance would simply improve the acceleration, the engine would still run without it, just not so well.

It doesn't even do that - when accellerating hard the vac advance does nothing!
It is a fuel economy device which advances the timing at light throttle (when cruising lightly) to give more power for the same fuel.

I'd also recomend a second opinion - anyone who diagnoses a car without looking at it properly (if that is really what happened, not just crossed wires) then I'd keep well clear.

[bmcecosse]

I agree with above - although the vac advance does help to 'brighten' the engine on transition from cruise to acceleration (when not working the engine is definitely 'dull'!). An other possibility here is that the little vacuum pipe or the diaphragm in the advance unit is leaking air and this is disturbing the engine when it drops back to idle ? It is indeed likely the vac advance is not working - they only last about 15/20 years - but this is unlikely to be the real problem here.
There are loads of pipes on ebay - here's a vac advance which looks like it will fit the 25D dizzy http://cgi.ebay.co.uk/P6-ROVER-2200-VAC ... 7C294%3A50

The advance characteristics may not be exactly corrrect - but will be near enough - especially as the original settings were for leaded fuel, which we don't have anymore!

[R_Parr]

I think the best thing to do is print off this page and take it to the garage.

Thanks for your help chaps,
Rhys.

[Declan_Burns]

I checked my vacuum advance today and noticed it's had it. I wanted to fit a new one but can't figure out how to get that little circlip under the micrometer adjusting nut off and back on again. Tried a mirror but whatever about getting it off I can't see how to get it back on. It's the 25D4 dizzy. Is there a trick to this?

[mike.perry]

It should come off with the help of a small pair of pliers if you wind the nut so that there is a gap betweenn the nut and circlip. Do it over a clean workbench, dining room table so that you can find it when it springs off. Refitting it is just a fiddly reverse of removing it.

[bmcecosse]

Just pop it off with a small screwdriver - to disappear for ever! As Mike says - best done where you can catch the clip. Not end of world if it gets lost - the thing will still work ok - there just the risk of turning it too far and it comes off the thread!

[Declan_Burns]

Thanks,
Mike, I think you are referring to the situation when the dizzy is removed. Sure, on abench it would be easy. I 'm asking about the situation when the dizzy is still installed. Should I remove the starter motor to get at it from below or should I remove the dizzy? Having said all that, I haven't even noticed it, Leonarda runs lovely! Maybe I should leave it as it is.

[bmcecosse]

Well worth renewing the vacuum unit - you will see a difference. Best to pop the dizzy out - it's only a few moments work - and give it a full going-over while it's out!

[Declan_Burns]

Thanks Roy,
Remove the dizzy? I've read through the manual but am a bit worried about loosing the timing. I have a TÜV (MOT) appointment on Tuesday so I don't want to touch it 'till then, in case I do something wrong. I reckon I sould mark-up the present dizzy set-up before I chance anything. I'm learning well but the timing issue is still a learning process for me.

[bmcecosse]

It will need resetting anyway after you fit the vacuum unit. Just undo the two fixing bolts - and don't loosen the clamp - and you will be very close when you refit, just the elongated holes to allow slight adjustment.

[mike.perry]

Use a dab of Tipex to mark the position of the distributor before loosening the clamp screws. If you lose the timing just turn the dizzy to fastest tickover which will be near enough. You can then fine tune it on the vernier nut.

[moggydriver62]

Its been along timesince I worked on them but possibly
the little flex wire,points to advance plate?

[Declan_Burns]

I did manage to get the old vacuum unit off as mike suggested but I didn't touch the dizzy and didn't loose the clip. It's a bit of a fiddle but a small mirror helps. New one is on and I took the car out for a 600km weekend trip. Running beautifully and when I took it for it's MOT it passed with flying colours. Now I have two years peace and quiet I hope. Thanks all.

[mike.perry]

Another satisfied customer

[bmcecosse]

Well done - our MOT was suposed to be going to two-year, but pressure from the garage trade (it's a nice little earner) has kept it at one year - and the cost went up again too! Why is it we have to harmonise with Europe for a whole bunch of stuff that doesn't suit us - but not with something useful like the 2 year MOT ????????

[Mogwai]

2 years is far to long people don't always check there cars properly these days & will go from service to service without even opening the bonnet . for example the amount of tyres I see worn to and past the cords is frightening

well done on the pass though

[mike.perry]

I agree, some people will not even check their lights from one MOT to the next