Hi all,
another newbie question I'm afraid. What is the vacuum advance? Is it the fuel pump? Where is it? Does anyone have a picture. I've checked Porters and Haynes but they are a bit vague about it.
The reason i want to check it is I am v worried about my fuel consumption.
Cheers Ben

phatbenny said:

What is the vacuum advance?
The reason i want to check it is I am v worried about my fuel consumption.

Click to expand...

As I understand it -

The vacuum advance cartridge does what it says:
when you have a high vacuum in the inlet manifold (normal light throttle running) the ignition timing is advanced (by up to 12 degrees).
As you've guessed, it results in more economical running (years ago cars didn't have this, as the fuel consumption didn't matter all that much).

The problem with too much advance is when you put your foot down - the larger volume of fuel air mixture burns more quickly, and you get pre-ignition (pinking) which damages the engine.

The advance caused by the vacuum unit reduces with the falling vacuum when you open the throttle, and when everything is set up correctly you get good economy on light throttle and no pinking when you put your foot down.

See picture for location.

Regards


John H.


P.S. Have you replaced your leaking fuel tank yet?
The tank normally operates under a slight positive pressure, so any hole will leak rather more running than standing.

Amazing response. Thanks John. That makes it much clearer.
I've heard all kinds of things, saying what you've said but not really explaining anything. e.g. "Well it advances the ignition doesn't it."

Just checking, there are not real considerations when changing it. Doesn't really mention it in Porter's or Haynes. I assume it's just bolt on bolt off.
Cheers
Ben

Two screws hold it on. It can be changed in 5 minutes. When my Panda 1000 FIRE wasn't starting the mechanic traced the problem to the vacuum advance unit. A replacement cost me £17.00 from Fiat.

phatbenny said:

Just checking, there are not real considerations when changing it. Doesn't really mention it in Porter's or Haynes. I assume it's just bolt on bolt off.
Cheers
Ben

Click to expand...

More or less:
two screws on the outside.

The tricky bit is locating the plastic arm on the ball on the pin on the insides of the distributor.

I found it a bit easier to do by taking the distributor off, and dismantling the top end of the distributor - but you may be young and flexible enough to see what's going on with it in situ.
If you take it off, scribe across the point where the distributor and head meet so you don't loose the timing when you put it back together.

Page 212 in my copy of Haynes - centre picture 9A-9B - shows the link rod and ball-stud I tried to describe above.

Thanks for advice, just changed it. It was indeed a five minute job, once I had spent fifteen minutes scratching my head and wondering how the hell to do it. What I couldn't work out was how to get the white plastic arm over the ball. The solution I came up with goes as follows.
Remove dist cap.
Remove distributor from engine.
Remove breaker and poorly fitting plastic thing.
Remove old vacuum advance.
Remove metal bow-tie shaped thing from top of distributor.
Put a tiny bit of grease on plastic arm, and position under ball joint.
Use a flat head screw driver in slot in plastic arm. Twist a bit to open hole a fraction more.
Use closed circle end of small spanner to hook the plastic arm directly under ball joint and pull up to push plastic arm onto ball joint. N.B. Make sure you do this from the sensible side, which will not leave you with a spanner stuck in your distributor.
Sorry if I'm telling you all how to suck eggs, but this might help a newbie like me.

On the down side I couldn't test it out as I managed to break the plastic tank joint from the top of the radiator, to the thin hose that goes to coolant reservoir :bang: . Oh well, will have to pick one up tomorrow from a scrappie or dealer. Must do this as the panda is going to be tuned in the afternoon.

John H said:

As I understand it -

The vacuum advance cartridge does what it says:
when you have a high vacuum in the inlet manifold (normal light throttle running) the ignition timing is advanced (by up to 12 degrees).
As you've guessed, it results in more economical running (years ago cars didn't have this, as the fuel consumption didn't matter all that much).

The problem with too much advance is when you put your foot down - the larger volume of fuel air mixture burns more quickly, and you get pre-ignition (pinking) which damages the engine.

The advance caused by the vacuum unit reduces with the falling vacuum when you open the throttle, and when everything is set up correctly you get good economy on light throttle and no pinking when you put your foot down.

See picture for location.

Regards


John H.


P.S. Have you replaced your leaking fuel tank yet?
The tank normally operates under a slight positive pressure, so any hole will leak rather more running than standing.

Click to expand...

Looks like my Panda can't read english I have problems with her again. My vacuum advance unit was replaced 5 days ago (leaking) and the engine is running strangely now. The first minute of idling it is ok, but as soon as you press the pedal it revs up to 1800rpm and stays there. The carb is not leaking (checked), spark plugs could be changed, distributor cap is clean, cables seems ok. The battery was off twice for mor than minute, but no diference.
I also tried with rotating the distributor and checked the point of ignition but it looks like it is ok.
The engine is FIRE 1108, 93-reg.

Does anybody on the whole world knows what might be wrong? Thanks for any advice.

you checked pipe to the vacuum advance unit for splits?

I didn't checked it phisicaly, but it looks like it isn't damaged any way. However, if it will be splited then there will not be so much sucking as it is. Without pipe it runs as it is expected but if I put pipe back on then revs are pushet up to 2000 rpm.

I don't know if it is right but I set the timing with vacuum advance unit uncoupled and with hot engine. Timing is app. 10° and there is no tinkling...

Whole thing looks like that diaphragm is too soft or that there is too much sucking which has a BIG influence on distributor unit.

set the timing with vacuum advance unit uncoupled and blocked off i think
not sure if 10° is right i'll go check haynes

it says 5° btdc static or with vacuum advance disconected
in the revisions for later models it say 5° btdc +- 2° static or vacuum advance disconected and pluged

my book only goes upto 1995 so i reckon your be the later model

Dave thanks for info. Today just arived new timig lamp so setup is going to be more precise. I'll try do it again this time with advance unit uncoupled AND blocked. Will se if there is any diference at all...hope there will be all set for november's MOT

dave said:

it says 5° btdc static or with vacuum advance disconected
in the revisions for later models it say 5° btdc +- 2° static or vacuum advance disconected and pluged

my book only goes upto 1995 so i reckon your be the later model

Click to expand...

I'm sure my 999cc FIRES (with carbs) had dynamic timing at 2 degrees btdc with vacuum advance disconnected and plugged. I'm also sure 10 degrees is way out and could be why the idle is so high, but I'm not familiar with the later SPi models so could be different