Hi
Hope someone can help as i have been trying to figure out various hose connections on my Daimler.
Does anyone know where the hose at the end of the 3/8 inch steel pipe connects to - this is the pipe that runs under the inlet manifold and comes out near the throttle body - the other end connects to the inlet of the throttle body.
Also, anyone know where the vacuum hose from the throttle body goes to?
Thanks!
Best wishes
George
Hi George, and welcome!
Daimler is correct but you basically have a Series 3 XJ with the upmarket Daimler trim. I’ve moved you XJ.
Is it a LHD, and is it a federal model with Lambda and cats or not?
David
Hi David
It is right hand drive - no cats
Thanks!
Best wishes
George
So that brings it pretty close to your car, David, doesn’t it?
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Right. Although mine has the later fuel rail - the black tube that runs from the firewall/heater and makes a 90° bend behind the block, then on to the water pump, see picture.
The other hoses are fuel feed and return, but I do have this manifold as a spare only. See the other picture from below; the two port tube is the feed and the single the return. What you have looks funny, I‘m walking to the car as I type this.
Sadly, I have no idea what the vacuum spigot is used for. My car was a mess when I got it. Federal (US) cars have the distributor on it as it’s ported vacuum - emissions. I have the climate control connected, but otherwise it should at least be plugged.
I hope someone can clear this up; I think I asked once and didn’t get satisfactory answers (otherwise I missed something).
David
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On the ‘European’ the throttle body vacuum connections is used for general vacuum, David - including ign, AC and vacuum throttle switch, interconneted by by various 'T’s and 'X’s…
There is also the separate hose connection between the AAV and the throttle body…
Frank
xj6 85 Sov Europe (UK/NZ)
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If so, what about the manifold vacuum port near cylinder 1? Not the drain, the one further up. I think the distributor has manifold vacuum. Why the AC should be powered off ported vacuum I don’t know… someday I’ll find an unmolested S3 and oh boy will I be taking pictures! I’m not saying you’re wrong, you do know better, but there must be more to it?
The AAV is connected through the air distribution block and into the throttle next to the PCV opposite of the small spigot.
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You can have manifold vacuum at throttle bodies as well as the manifold itself, David. It depends of the relative positions of the ports and the throttle butterfly. Some carbs have two spigots, one for ‘manifold’ vacuum and one for ‘ported’. On the xj, a separate spigot on the throttle body gives ported dist vacuum - as shown on Georges picture…
In shorthand we say ‘manifold’ vacuum to denote the vacuum in the manifold, while the source itself may be elsewhere. (The fuel pressure regulator uses a spigot on the manifold - which on 'European’s might equally be used as a dist vacuum source). Likewise, we generally use ‘ported’ vacuum for vacuum that is directly affected by butterfly position.
The observable difference at spigots is that ‘manifold’ shows manifold pressure any time - while ‘ported’ vacuum shows zero vacuum, or thereabouts, with the throttle closed, and varies directly with throttle position. In this context; 'ported vacuum would indeed be useless for the AC…
The point of the AAV is that it takes air from AFM side (top hose), taking measured air through the AFM, and deliver it (through the bottom hose) to the air distribution block into the manifold side of the throttle body - bypassing the closed throttle. It might as well be connected to a manifold spigot. But as AAV is clamped to the water jacket for heat pickup, and the idle screw is incorporated in the air distribution block; Jaguar engineering…
As an aside; carbs use internal port, suitably placed, to control fuel mixture - so ‘ported’ is a loaded term…
Frank
xj6 85 Sov Europe (UK/NZ)
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Well - now you tell me what the port on the throttle body is good for in the europeans.
It can’t be for the full load switch or the distributor. It makes no sense for the heater. The regulator needs and had a manifold port. So?
I have three throttles and all have spigots as shown, ported.
The best way to test if a spigot has ‘manifold’ or ‘ported’ vacuum is to measure, at the appropriate hose, with a vacuum gauge with the engine idling. And I assure you; my AC, dist and full load vacuum switch has manifold vacuum…
Since the original question was about the vacuum connections; why have two spigots with ported vacuum when only the ‘US’ distributor needs it…?
Frank
xj6 85 Sov Europe (UK/NZ)
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That helps.
I see one vacuum port, the one at the bottom, and we still don’t know what it is for. ANY European/ROW S3 owner who could have a look?
And I am very sure that this is ported as the pinhole is drilled right ahead of the throttle and my AC eventually loses power at idle…
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I have one vacuum hose serving all users via 'T’s and an ‘X’, David - which is inconclusive; neither ‘consumes’ vacuum. Ie; all users are sealed so very little air movement is involved.
However, one of the ‘twin’ ports are connected to the air distribution block and the block serves both the AAV and the idle screw - requiring air flow, at least with throttle closed, bypassing the closed throttle. Obviously; out of idle, throttle moved, neither are required to run the engine - engine gets all air required via the opened throttle.
Where the other ‘twin’ is connected (metal pipe?) goes I know not!
Point is that the ‘twin’ ports gets air through the AFM, measured for fuel computation - the air flow through one is controlled by the AAV and idle screw, the other…?
The vacuum at either, if any, may or may not vary with throttle settings - vacuum is irrelevant for AAV and idle screw; they function by air flow. However, with throttle closed the ‘twin’ ports have ambient air flow…
The ‘third’ connection is interesting - since you have a throttle body in your hand. Theory dictates that air pressure falls as air flow speed increases - a constant air flow through a narrow passage, like the throttle gap, makes for high vacuum. Increasing with air speed and volume - tied to engine rpms (engine air consumption) and throttle setting.
So the critical point here is the exact position of a port in relation to the butterfly edge. If the port is near to the butterfly edge, or below, in idle; the port will have high/manifold vacuum - air passing at high speed…
Frank
xj6 85 Sov Europe (UK/NZ)
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To the crankcase, Frank…? So not exactly measured, but a mixture of burnt gases and fueled air, no urgent need to measure. I do not care about the two large ones, one is to pick up air bypassing the throttle and the other is not wanted at idle as there is not much blowby and the required vacuum thus low.
Only the other is interesting.
David
Hi guys, thanks for all the input, but my head is in a tizzy and I still have not solved the hose connections on my Daimler Sovereign - could it be that my setup is different from a Jag XJ6 4.2? Don’t know, but the connections that people have been suggesting I cannot find on my car.
I have put together a simple diagram to see what connections i am missing, namely:
HOSE A - comes out of the end of the water rail, just above the water pump
HOSE B - connects onto a 3/8 inch steel pipe that runs below the inlet manifold
HOSE C - the other end of this pipe
If anyone can crack this I will be DEEPLY APPRECIATIVE!! 
Daimler Sovereign 4.2, Series 3, 1981.pdf (147.8 KB)
Thanks again!
George
Hose A is from water rail to heater valve or matrix. Hose B is from the matrix or heater valve to the steel tube pictured in my first answer. Hose C is a short piece towards what must be the water pump.
None of these have vacuum.
David
https://www.angloparts.com/en/catalogues/group/2228/jaguar-xj-heater-and-air-conditioning-xj6
13, 15, 16…?
Cute drawing (thank you), the throttle body is also plumbed as you were drawing, so the throttle doesn’t ice up. On my previous photo, below the two big air inlets.
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Not actually to the crankcase itself, David; to the crankcase ventilation system - makes perfect sense. Not much air is drawn, and mixed with fresh air from the AFM, the crankcase oil fumes are indeed combustible…
The other ‘twin’ port cannot bypass the throttle - it must be connected, somehow, via the air distribution block to ‘manifold’ vacuum - bypassing the throttle…
Like George, I find it muddier and muddier. And definitely; the set up varies over the range - the ‘book’ shows a different set-up from mine - so George is likely right there too. Doesn’t make his task easier…
Frank
xj6 85 Sov Europe (UK/NZ)
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So, to the crankcase.
I think you’re confusing a little, respectfully, anyways: having cleared up the water plumbing, what’s the vacuum port for?
Wish I could help.
David
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With the throttle closed there is no vacuum at the two ports, David - the bypass is through the air distribution block, which is (somehow) connected to ‘manifold’ vacuum, delivering air through the AAV and idle screw. As the throttle opens; the adb port is basically superfluous - air is mainly passing the opened throttle. The crankcase vent port draws air from the crankcase through the open throttle.
Leaves me in doubt as to where the vacuum to the AC etc comes from…
But George can consider it as gospel one of the two port goes to crankcase ventilation as you say. And somewhere on the route; the charcoal canister (if fitted) vacuum line is connected to it…
Frank
xj6 85 Sov Europe (UK/NZ)
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George only wants to know what the little spigot is for. The other four are clear and obvious.
The air distribution block has the AAV and the overrun valve and the idle air bypass… none of which can be misconnected. The little spigot on the TB either has some purpose, or it has to be blanked off.
