Xj6 series 1 4.2 litre 1972 breather pipes

XJ
#1

I have just started a restoration project and noticed a couple of breather pipes missing on the engine. Can anyone tell me please where these should go or terminate?

One is the top front hose from the engine breather outlet (which at the moment just ends at a very short length of rubber hose on the housing cover).

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The other missing connection is the lower pipe outlet on the carburettor’s automatic enrichment device (AED) - which may be the cause of my troublesome starting (but once started it seems to run smoothly, but with a high tick over). I’m yet to check or adjust the carburettors, and don’t know if the AED is adjustable other than looking at its filter. I thought this outlet on the AED was the fuel overflow pipe, but the slightest movement of my finger in front of it rapidly effects the engine running, and my finger within 1/2" of the outlet makes it splutter and if left there or moved closer the engine dies.

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#2

The breathers come up to the carbs. I have a '72 as well and the pipe orientation is different to your drawing. I can send a picture if that helps. The AED should have a ducting tube running from the rear exhaust manifold up to the underneath the unit - this is the “heat message” input and the AIR INPUT, when it’s operating in “choke” mode. The blue arrowed coupling is for the AED overflow - just as the main carbs drain overflow so does the AED, usually if the needle/seat fails. The AED will not be operating properly with the duct disconnected. Heated manifold sourced air switches it off. The AED is adjustable, in some instances the adjustments are set and capped off, but these can be removed. The factory manual describes AED operations well. Paul.

1 Like
#3

Yes the first pipe goes to the air cleaner - if you have the correct housing.
As Paul said, the second is the AED overflow, But I am not sure that you will need the heated air pipe to the AED as your setup looks to have a manual means to turn the AED off. This setup is worth keeping.

#4

Yes, I should have looked more closely! That AED has the manual conversion. The cams work the mixture and airflow. You might be able to get the instructions on line. Paul.

#5

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Your picture shows that your AED has been modified to manual choking, David - external cams…

Which means that manual action is required to work the AED. The ducting pipe, normally takes air through the hot air pick from the air filter - but the hot air pick-up, mentioned by Paul, is redundant with manual choking. It’s function with automatic operation is, as the the engine heats up, that the hot air shuts off air to the AED - turning it off. With manual operation, air is shut off by pushing in the choke. Provided the hot air pick is not clogged, a common source of AED failure, the original air connections to the AED can be retained…

The blue arrowed connection indicates the balance pipe - connected to the air cleaner for filtering, or to open air…

Frank
xj6 85 Sov Europe (UK/NZ)
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#6

Thank you for this helpful information. I think I now need to investigate the manual choke and cable, as the very slightest change in position is the difference between the engine starting or not - so that’s clearly effecting the AED.

Does anyone know how the manual conversion of the AED should be done and set up?

#7

David,

please post some better pictures of the manual conversion of the aux carb - just to make sure you get the right explanation.

In any case: this is not just a “normal” choke setup with enrichment + additional air, but an extra carb feeding into both intake sections. So check the rubber elbow pipes to begin with.

The aux carb in itself is a fine piece of machinery and veeeery sensitive to changes both in fuel or air, as contolled by those two cams sitting on the shaft. Really small differences here make a world of difference in particular to cold running. Maybe you check the clearances at the cams whether they are correct - I add the instructions that came with my kit, but, again, pls check whether yours is the same.

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Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

2 Likes
#8

Thank you for the details. I think I have the same part fitted, so I will investigate your set up information. These are the best photos I have at the moment:

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#9

Hmmm.

They look identical, except yours is mounted the opposite way as regards the choke cable, it seems.

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In my car the cable is on the front side and comes in from the right hand (RHD car! What is yours?). If you look closer you notice the shape of the bottom of the cam cradle follows the shape of the base part in my car, while the cutouts of the cam cradle on your part seem to be ill-fitted. As the cam cradle is fixed with two screws and a flat surface it may have been mixed up somewhen in the past - or, as the wire looks fairly short in your car, this may have been done purposefully to cope with the lack of wire length. Either the cams are not adjusted correctly or an over-tight wire may result in malfunction.

You might first check whether tension in the wire cable compromises function. In case of doubt I’d throw in a new wire (they seem fairly standard). Then you might check the instructions in 2.3.e whether the clearances are correct, if necessary adjust them, and that should be it.

Best

Jochen

75 XJ6L 4.2 auto (UK spec)

#10

Yes I will check the bracket position, as it appears to be 180 degrees different to yours. I think the cams are equally spaced, so should work with the choke cable being either side provided the cams are set correctly. However if the cams were set for the optimum performance as mentioned in 2.3(f), and then the cradle bracket fitted incorrectly 180 degrees around the cams would be on the wrong tappets.

There is some slack in my choke cable and it appears free running to fully open or close the fuel and air tappets. I will go through the set up and test procedures of paragraphs 2.3 and 2.4 in your instructions.

My car is right hand drive UK car. It has only been driven 12 miles since 2014 and left in a garage. I don’t know when the manual choke was fitted, although I was made aware when I first collected the car that there was a starting and tuning issue.

#11

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The spring itself should bring the AED to the ‘off’ position, David, both plungers fully depressed - and yours do not seem to do that…?

In theory; the cable slack is there to ensure that the the AED goes to the ‘off’ position with the choke fully pushed in. Ie, the cable is not meant to ‘push’ the AED into the ‘off’ position.

That your idle is high implies that the AED is not fully off. In setting the up the AED; you need to set up the carbs first, to ensure that the carbs do not interfere with AED reactions/test specs. Setting up the carbs require the engine to be fully hot - and the AED verified in the ‘off’ position…

Frank
xj6 85 Sov Europe (UK/NZ)
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#12

Frank is right, as usually …

try to start the car with the choke, then fully warm up the engine before you pull off the two elbow pipes and block them securely. Then restart the car and tune the carbs!

But be aware that depending on the condition of the manual AED device and the prior condition of the carbs you might not be able to re-start the cold engine. So you better dive into fixing the manual AED operation issue before the engine is stone cold again (don’t worry though - an early ROW car will be tuned rich enough to need a cold start device only once a day under British weather conditions.

BTW, I’d get myself one of these wires, just to be prepared. Your wire obviously has been made subject to a lot of experimenting and is extremely short. It looks like it used to be under more tension - you can see the dent in the wire. Maybe the wire has slipped through a bit? Just for curiosity I’d try this position again. Might be an easy fix before pulling everything apart …

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

#13

Thanks for the additional information. I will be investigating this and working through all the points raised.

#14

Since engine reaction is used for checking AED function, David, it’s very important that the carbs are set up correctly…

The carbs are always in play. The AED is just a ‘starting’ carburator - adding fuel and air to fatten the mixture and increase idle as required by a cold engine. Which also means that if the AED is activated with the engine hot; the engine will react. And, of course, without the AED the starting will be impaired - a not infrequent PO reaction to difficult starting due to AED trouble is to detune the carbs…:slight_smile:

As Jochen says, in moderate climates the engine may start without the AED - and manual use requires some experience for best results. With a well working AED in automatic function - the right setting is done by the devise itself…

Frank
xj6 85 Sov Europe (UK/NZ)
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#15

Before I adjust anything I am going to do a full engine service, as it has been stood since 2014, so just waiting for parts to arrive.

I have noticed that the air intake tube of the AED has a shrink tube fitted on the end which just has a small gap of a couple of mm or 1/8". That can’t be right!! Not sure if it’s a cut off length of tube that has just shrunk with the engine heat or someone’s attempted modification. Am I correct that this should be just an elbow type air inflow pipe with no restriction, and would it normally point downwards to prevent debis dropping in (the AED modification drawing shows this pointing upwards).

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#16

David,

in an ideal world the air intake of the aux carb should be fed with filtered and pre-heated air, i.e. from the air filter box. In a Jaguar world the aux carb has to do with the cold air from around. I’m happy to check out tomorrow what my air intake looks like.

Then again, chances are you already found the culprit of your poor cold starting - the aux carb can’t do much, if suffocated!

Best

Jochen

75 XJ&L 4.2 auto (UK spec)

#17

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Air hose to the AED is originally taken to the hot air pick-up, on the exhaust manifold, then to the air filter/carb intake. Air is heated in the hot air pick-up and the AED automatically adjusts the air bypass and fuel according to engine temp - to be fed into the inlet manifold.

In manual mode regulation is done by cam actions as set by the driver, and in principle air flow restriction is all done within the AED. Ie, the air flow restrictions by the shown arrangement may or may not interfere with manual AED set-up - but it looks fairly ‘professional’…

I suggest you first attend to the carb settings - verifying that the carbs work as they should with a hot engine, and the AED closed. Then you can experiment with the AED itself, eventually removing the restriction for testing - and/or connect the AED intake to the air filter. At present, we do not know if the hard starting is a carb or an AED problem…

Have actually tried using the manual choke for cold starting…?

Frank
xj6 85 Sov Europe (UK/NZ)
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#18

Whilst I’m waiting for my parts to arrive for a good service (don’t want at the moment to start the engine for a long warm up then take off the AED for the carburetter check) I have checked the small fuel filter - this was full of rubbish.

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It is now cleaned and the incoming main fuel filter checked - which was very clean, but a new one on order. I suspect the AED filter has not been checked before. Old fuel in the tank drained and some fresh put in, with fuel line flushed and pleased that no rubbish came out.

The engine, with manual choke, did fire up better with less spluttering but tick over high still. More checks and set up when my parcel of parts arrive for its well needed service (last one done in 2013, although car has only done 12 miles since then).

This is the current restricted end on my air inlet tube - looks more like a rubber boot someone has put on. It will be coming off!!!

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#19

David,

indeed that that rubber boot on the air inlet is totally wrong and maybe spoiling your party!

Sorry, I got distracted in my last post by that “air supply” in the sketch of the manual conversion instruction and totally forgot that the original aux carb/AED combo uses only one air intake both to provide the aux carb with air and (!) to heat the bi-metallic strip used in the upper black part of the AED to make it an “automatic” enrichment device.

The rubber tube fitted at the “air supply” turns down and rearward to be supplied with air taken from underneath the exhaust heat shield at the rear exhaust manifold. This air is led in an insulated pipe around the rear end of the engine. In many instances the AED just wouldn’d work any more (i.e. “shut down”), because the heat insulation had deteriorated and the heated air ducted to the AED never was hot enough to allow the bi-metallic strip to fully close.

I made only poor pics showing the way downward and the main insulated air duct - in your car someone may have done away with this thing as with the manual conversion kit it is no longer needed.

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And yet, the original setup provides for some kind of filtering at the intake.

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C.33323 feeds into the air intake of the AED lower part. C.33346 is a filter element.

So, if the rest of the whole shebang is still around, I’d simply reconnect the air intake of the AED with that piping, if not, I’d probably use an open rubber tube with some sort of filter to keep any kind of particle out of the engine intake.

Good luck

Jochen

75 XJ6L 4.2 auto (UK spec)

#20

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Hot idle is a carb adjustment procedure, David - the AED, working properly, plays no part. AED is only used during cold start and warm-up - but with a faulty AED a PO may detune carbs for better cold starting - resulting in high hot idle. And a faulty AED may also cause a too high idle - tuning carbs without AED interference is mandatory…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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