Vacume system on A bank side
#21
#22
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Yes. It goes from a vacuum source....not sure which one....to the Marelli ECU
This is annoying... Trying to find some explanation for the vacume routing is dreadful...
I hear ya.
Cheers
DD
#23
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Ah, yeah, I now remember... Behind the dash or somewhere beneath it was the Marelli ECU with a vacume connection. That would be the black rubber hose connected to the bulk head. The heating system aka AC uses a red plastic tube... Which get's it's vacume from the little solenoid which, like in Volvo terms, must cut the vacume supply to the AC system in case of a full throttle position where there is no vacume in the intake manifold...
The Marelli will always get it's connection and needs to know if full vacume (idle) or partial (normal driving) or none (full open theottle) to adapt the ignition...
Finanly it makes sense... Until someone comes and ruins it
Meaning the blue valve only works for the AC, the front take off goes straight to the cruise bellows and the rear take offs being for Marelli, tranny and climate control with vacume switch and full load switch...
The Marelli will always get it's connection and needs to know if full vacume (idle) or partial (normal driving) or none (full open theottle) to adapt the ignition...
Finanly it makes sense... Until someone comes and ruins it
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#24
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Hi Daim
Tracing all those Vacuum Pipes would take me time that I don't have at the moment, as they just seem to disappear at the back of the Firewall.
I've got to get my own Car done, while the Weather is good, as its usually chucking it down with rain at this time of the Year.
Hope you understand about that, as it would take me a lot longer than you would think.
But as with Doug, I do share that frustration.
Tracing all those Vacuum Pipes would take me time that I don't have at the moment, as they just seem to disappear at the back of the Firewall.
I've got to get my own Car done, while the Weather is good, as its usually chucking it down with rain at this time of the Year.
Hope you understand about that, as it would take me a lot longer than you would think.
But as with Doug, I do share that frustration.
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Ah, yeah, I now remember... Behind the dash or somewhere beneath it was the Marelli ECU with a vacume connection. That would be the black rubber hose connected to the bulk head. The heating system aka AC uses a red plastic tube... Which get's it's vacume from the little solenoid which, like in Volvo terms, must cut the vacume supply to the AC system in case of a full throttle position where there is no vacume in the intake manifold...
I'll always allow the possibility that I'm wrong but I really don't think the blue solenoid solenoids(s) have anything to do with the climate control.
My '88 V12 had the two blue vacuum solenoids and the MKIII climate control (as does your '89) and neither were related to the climate control.
The climate control uses a black/white check valve to take care of the full throttle thing....at least on every V12 I've touched.
The Marelli will always get it's connection and needs to know if full vacume (idle) or partial (normal driving) or none (full open theottle) to adapt the ignition...
Right, and that should be a red plastic vacuum tube, thin. But maybe there's more than one red vacuum tube? That much I don't remember.
Cheers
DD
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The check valve for the climate control vacuum is either near the vacuum reservoir or near the bulkhead where the climate control vacuum hoses go through.
(I might be getting Series III V12 stuff mixed up with XJS V12 stuff!)
On my Series III V12 the check valve is hear the bulkhead/firewall
Is yours a German market car?
Cheers
DD
#30
#31
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If you have the timer for the 45 second supplemental air valve at start then this system would also activate the solenoid to dump vacuum from the Vac adv capsule to eliminate advance at startup. This helps heat up the O2 sensors more quickly.
#32
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I was referring to the vacuum advance capsule. Or is yours a Marelli?
If you have the timer for the 45 second supplemental air valve at start then this system would also activate the solenoid to dump vacuum from the Vac adv capsule to eliminate advance at startup. This helps heat up the O2 sensors more quickly.
If you have the timer for the 45 second supplemental air valve at start then this system would also activate the solenoid to dump vacuum from the Vac adv capsule to eliminate advance at startup. This helps heat up the O2 sensors more quickly.
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#34
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ah, of course. You already said as much. My excuse? It was middle of the night.
ROW spec cars have a 15 minute timer and do the same as US models with that system but for different reasons.
ROW spec cars have a 15 minute timer and do the same as US models with that system but for different reasons.
Last edited by JigJag; 04-18-2017 at 12:01 PM.
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#37
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I'm stumped, obviously. I think what this may come down to is to (somehow) trace down a vacuum schematic specific to your *exact* build specification. One has to exist somewhere.
On the bright side, you don't have the complex canister purge scheme, the even more complex vacuum advance system, cruise control dump valve, air injection diverter valve, climate control reservoir, nor brake vacuum assist. So, relatively speaking, you have it easier that many![Smile](https://www.jaguarforums.com/forum/images/smilies/smile.gif)
Cheers
DD
On the bright side, you don't have the complex canister purge scheme, the even more complex vacuum advance system, cruise control dump valve, air injection diverter valve, climate control reservoir, nor brake vacuum assist. So, relatively speaking, you have it easier that many
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Cheers
DD
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Daim (04-18-2017)
#39
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Yeah, easier is of course great, if only it would be clear WHAT the blue solenoid actually DOES do...
I have the same connection on the A bank throttle body which runs forwards, then under and goes into a grey and black one way valve. This then leads to the blue solenoid and is switched... The metal tube of the solenoid also connects to the intake manifold (rear). The 90° connector goes somewhere else and as far as I can tell, into a red plastic tube which heads to the left side of the car (most probably to the glove pocket where the Marelli ECU sits). But why would this need to be switched!?
The other connector as it looks deals with the switch on the intake (that plastic lump with two cables) and then to the AC system.
But again, WHY would the Marelli ECU need a switched vacume? Isn't it obvious that it needs a constant vacume supply which would let off at higher RPM and grow at lower RPM so it can determin if the timing needs to be retarded (like me
) or advanced (like everyone else
)??
Anyhow, as it looks, the blue solenoid seems to be for the Marelli ECU.
I have the same connection on the A bank throttle body which runs forwards, then under and goes into a grey and black one way valve. This then leads to the blue solenoid and is switched... The metal tube of the solenoid also connects to the intake manifold (rear). The 90° connector goes somewhere else and as far as I can tell, into a red plastic tube which heads to the left side of the car (most probably to the glove pocket where the Marelli ECU sits). But why would this need to be switched!?
The other connector as it looks deals with the switch on the intake (that plastic lump with two cables) and then to the AC system.
But again, WHY would the Marelli ECU need a switched vacume? Isn't it obvious that it needs a constant vacume supply which would let off at higher RPM and grow at lower RPM so it can determin if the timing needs to be retarded (like me
![Big Grin](https://www.jaguarforums.com/forum/images/smilies/biggrin.gif)
![Big Grin](https://www.jaguarforums.com/forum/images/smilies/biggrin.gif)
Anyhow, as it looks, the blue solenoid seems to be for the Marelli ECU.