Vacuum Advance much ado about anything ?

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ashbash2403

ashbash2403

New Member
Posts
79
Location
Walsall area West Midlands
Recently failed MOT on CO and HC (3.9 1990 EFI).
hour or so with a tuner and the MAF was tweked along with the Dizzy which was adjusted way out... (36deg).

Now running nice & lean (a bit too lean).

He said the Vac Advance was gone....
He came to this conclusion by taking the vac hose off at dizzy end while running and got his tongue stuck to the hose so the engine is pulling :)

But with the Dizzy cap off and the vac hose off from plenum end and sucking,, no movement from arm or plates (although the plastic cover under the cap is not very clear to see through and no vaccum held i.e. no release when taking tongue off hose (like you do with a straw full of water)....

As the Vacuum Advance costs about as much as a working second hand Dizzy would it be best to swap the lot ot go for a NEW Vac Advance or test something else first.
 
ashbash2403 said:
Recently failed MOT on CO and HC (3.9 1990 EFI).
hour or so with a tuner and the MAF was tweked along with the Dizzy which was adjusted way out... (36deg).

Now running nice & lean (a bit too lean).

He said the Vac Advance was gone....
He came to this conclusion by taking the vac hose off at dizzy end while running and got his tongue stuck to the hose so the engine is pulling :)

But with the Dizzy cap off and the vac hose off from plenum end and sucking,, no movement from arm or plates (although the plastic cover under the cap is not very clear to see through and no vaccum held i.e. no release when taking tongue off hose (like you do with a straw full of water)....

As the Vacuum Advance costs about as much as a working second hand Dizzy would it be best to swap the lot ot go for a NEW Vac Advance or test something else first.
Click to expand...


Think from memory your engine should be around 8 degrees static. You will then get an advance as bob weights move out, after start up, you will then get a further advance as engine revs by vacuum. You need to put a timing light on it and check if it is being advance properly. If it's not and is running retarded at high RPM it will get pretty hot. Burned valves pistons Etc.
 
EFI runs at 4 degrees +/- 1 degree (dynamic, vac disconnected) if non-cat and 5 degrees +/- 1 if cat.

Vac advance will mean poor throttle response and I have also known it to cause a problem with stalling when coming to a stop - I suspect that is because you essentially end up with an inlet air leak.

Anyway, a vac unit is quite expensive but if you buy a used dizzy you have no way to know if the vac unit is good or that the dizzy is good. Personally I would take the pain and buy a vac unit to put on a known good dizzy.

If you suspect vac unit, take hose off at plenum inlet and suck - if you can suck air through it then diaphragm shot. Hope that helps ya.
 
you wont move dizy unit by sucking..not unless you are a ho** and get plenty practise..lol..
 
you may be right..gonna suck on my spare dizzy tomorrow..let you know..lol..
 
Just get a new one.it doesn't have to be for a landy,just correct drive and four cylinder.look on ebay they are going for around the £40+ mark.
 
Bought a re-con unit from ignitioncarparts.co.uk about 18 months ago for £130 inc new coil.
Comes with a 2 year warranty and a £25 refund on the old unit.

No problems at all so far and it's an easy fit, just one 14mm bolt.
 
Did the suckometer test :) engine does indeed suck like a vegas hooked but when I take the plenum end off and suck it sucks like a straw and you can blow and no movement in the dizzy at all...
Happy to get either just the VAC advance or can pick up a dizzy and spend the extra dosh now... Seen these powerspark ones advertised but not sure if they are rated or not ?? So a Vac Advance for 8 Cyl engine would be fine if I can find one for decent money ???
 
Anyone Seen these Powerspark Dizzys kits done by Simonbbc ? £100 for the dizzy Lucas Coil and 3 to2 pin convertor as a bundle.... not seen much write up of them but any reviews I found are all good...
 
Did contact the Doctor but he said I was too NEW car wise for his stuff.... Powerspark guy says he will do the High Energy 3.9 V8 DIzzy with Red rotor arm 3 to 2 wire & new lucas coil bundled for £99 delivered....
 
Did you look on fleabay yet,there are brand new ones on there that are cheaper and i think they were Lucas/bosch ones.
Failing that go for that one if you think the brand is OK,Iv'e never heard of them so can't comment.
 
Ordered one of the Powerspark Guy in Bromsgrove... winging it way to me as we speak should get it in tomorrow and get some of thay shinyness off it as it will make the rest of my engine bay look bad :). Will update once Dizzy and Coil in and how the vac advance changes (by now having it). Got Black Bosch HT lead so not keen to replace those for the sake of it unless a good idea...
 
Kit Came Next day and its all fitted....
Had one head scratching moment where we had no power at all in to the coil even though wires went on as they came off (2 new from 3to2 convertor) ones plugged in correctly).
Meter on it revealed no power to the coil... plugged the + wire from the 2 which use to run from Dizzy to coil and hey presto life ! but this wire should be dead so someone has been doing some tinkering...
 
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