Aed conversion to Manual Choke

(keith Smith) #1

Good evening all.
On my xj 3.4 i have the dreaded AED , this has been converted to manual operation, i am looking to find the setting for the fuel needle to suit the manual operation.
I have the basic setting for the AED, but not for the conversion. If someone could advise that would be great.


(Jochen Glöckner) #2


if you relate to the common AED conversion kits, they do not replace the aux carb and consequently you do not touch the setup of the main carbs - except, of course, to balance and tune them correctly with the aux carb blocked off and a hot engine.

The conversion kit is in fact a cable operated shaft with two cams for the air and fuel supply of the aux carb. The gaps are critical.

Good luck


75 XJ6L 4.2 auto (UK spec)

(Frank Andersen) #3

What are the symptoms you encounter that require attention, Keith…?

As Jochen says; the cam operated conversion utilizes the AED as is - eliminating only the thermostatic controls. Other faults inside the AED are not bypassed by the manual conversion…

In principle; the AED fattens fuelling and increase idle rpms by adding air flow depending on coolant temps - or manual setting. ‘Off’, engine hot - no air flow, no added fuel; engine runs on the main carbs as set, as Jochen implies…

xj6 85 Sov Europe (UK/NZ)

(keith Smith) #4

Hi Jochen.
Thank you for the information, the pictures you supplied are exactly what i have. would you have any idea on base setting for the

mixture adjusting screw on the aed when fitting this manual system please.


(keith Smith) #5

Hi Frank.
This car has been truly messed with by a Garage that has no idea. Symptoms are super rich on start up, difficult idle.i have replaced all available parts within the AED with a kit that i purchased.

Now wanting to set up the Aed with manual operation kit (choke ) that came with the car. With some idea of base setting of the mixture adjusting screw i can move forward.


(Paul Breen pay palled it) #6

Hi Keith, Jochen beat me too it with the pictures. I am away from home at the moment - should be able to find the installation instructions to go with the pictures on the weekend. Paul

(keith Smith) #7

Hi Paul.
If you could find the instructions that would be superb.

Thank you


(Robert Laughton) #8

I’m watching this too. I have a Belgian XJ6 with a non-operational AED. I start I’ve been squirting fuel into the breather ports. Where did you find the kit? I didn’t see it at Burlen’s site.



(keith Smith) #9

Hi Rob.

Mine was on the car when I had it at Christmas.

One is for sale on eBay

They are not cheap.

Hope this helps.



(Frank Andersen) #10

I thought you already had the manual conversion, Keith - which is causing trouble…??

Have you tried blocking off air and fuel for the AED - to verify that the problem is not caused by the carbs themselves…?

The AED works like an ordinary carb; the lift of the needle regulates mixture, and a separate function regulates air flow. The two are synchronised; using coolant temp to lean out mixture as the engine warms up - adding that manifold vacuum is used to enrich mixture during acceleration. In the common manual conversion, cams are used to vary air flow and needle position - but I’m not sure needle adjustment has a wide enough range to account for your symptoms…

The gist of this is that in auto or manual mode, AED shut off, there is no air flow through the AED - and needle position is immaterial. With no air flow; petrol cannot be sucked via the needle into the manifold…

One possibility; a leak in the vacuum capsule/seals will draw raw petrol directly into the manifold - causing very fat running at all times. Have you tried disconnecting or clamping the vacuum hose? A fault like this will be just as bad in auto or with manual…

xj6 85 Sov Europe (UK/NZ)

(keith Smith) #11

Morning Frank.
Yes i did have the manual kit fitted to the car when i purchased it.

I thought for the cost of replacing diaphragms etc within the unit it was a starting point,and it was . It had been stripped

prior to me with parts not fitted correctly to the air valve section especially, and fuel diaphragm had fuel either side of it indicating

a split.

I will certainly try your suggestions Frank and reply with my result.

Thank you again


(Jochen Glöckner) #12


sorry I was out the last days.

If your system is as messed up as you descibe you’re probably best advised to first get that car started, just somehow. Then warm up the engine and block off the aux carb completely. Now have the carbs balanced and properly tuned. This is just to get one safe room to begin from …

The aux carb is often described as not serviceable and the Parts catalogue lists it only as a single part (1K 04L). The only thing you’re supposed to service is the AED filter (19.15.43), the gaskets, the needle valve (19.15.42), the diaphragm (19.15.40) and the spring. You seem to be well into that routine.

The internals of the aux carb are virtually untouchable. No people I’ve talked with about the AED conversion ever had any issues about the lower part of the aux part except for the routine maintenance parts mentioned. Chances are that even the GWC (Garage without a clue) hasn’t managed to mess anything up in the internals of the lower part of the aux carb.

I enclose the mounting instructions. It is just your mentioning of the “mixture adjusting screw” that confuses me - there isn’t any on the aux carb. Mixture is all controlled - originally by a bimetallic strip and following the conversion - by the positioning of the two cams and the size of the gaps.

Last caveat: the conversion kit expressly recommends to let the cams’ position on the shaft unaltered. Your GWC might have ignored that advice.

Good luck


75 XJ6L 4.2 auto (UK spec)

(Paul Breen pay palled it) #13

Beat me again Jochen! I’m going up to the garage today, If mine are in better shape than yours are I will post them to get square:slightly_smiling_face:

(Jochen Glöckner) #14

Sorry, Paul, didn’t mean to hurt you :slight_smile:

My copies aren’t that bad, btw. This is probably one of the best features of the new sites. It’s really easy to upload pics, no more size limitation and easy downloadable to be magnified again, so that even ant-like lead letter crawlings become legible again …



75 XJ6L 4.2 auto (UK spec)

(keith Smith) #15

Hi jochen.

Thank you for taking the time to try and help me.

Some great suggestions made by you and this weekend, weather permitting carbs will be stripped cleaned

And balanced.

With regards the Aed mixture screw, when I removed the Aed the fuel screw was wound all the way in ,according to my research

And pictures I have the mixture screw should have a measurement of 8.4 MM. from base unit to top of square head on the screw.

Mine was showing 4 MM ,just trying to establish the correct setting for this needle/ screw before I refit with the manual choke operation.

Again Thank you.


(Jochen Glöckner) #16

No problem,

as a matter of documentation - as you have opened up the aux carb obviously, it would be wonderful for other users in a possible similar situation to see what’s ahead of them. So maybe you manage to take some simple pics and show the source of evil.

Good luck tomorrow


75 XJ6L 4.2 auto (UK spec)

(Paul Breen pay palled it) #17

All good. As we were putting our car back on the road after 24 years I used up some of the parts I had built up for posterity. One was a brand new AED unit my wife bought at Henlys in London when she was a slip of a girl. It had played up a bit so I bought the conversion you pictured. I then got the new AED to work perfectly - so progressed no further. Might fit the conversion to the old AED so I’m ready! Paul

(Frank Andersen) #18

Another problem may be float level in the AED - causing excessive fuelling while the AED is active. Clamping the fuel hose will eliminate any fuelling from the AED - basically verifying if the fat running is caused by the AED. As Jochen also says - it’s important to absolutely verify that the carbs are working as they should. Which is impossible to verify if the AED misbehaves…

As an aside; the adjustment screw acts on the main bimetallic spring - which affects both fuel mixture, needle position, and air flow. But crudely; the further down the adjustment screw is set, the fatter the mixture…

xj6 85 Sov Europe (UK/NZ)

(Jochen Glöckner) #19

Nice story, Paul!

as I got my car with the conversion kit mounted and the original AED parts in a bag, I can’t speak from my experience, but it seems that many cases of a “malfunctioning AED” may really have been a deteriorated hot air line insulation. It’s hard to believe that bimetallic strips regularly deteriorate within a couple of years - that’s what many people speak of the AED control. After all, our mothers’ flattening irons were all controlled by bimetallic strips and went for decades.

BTW, do you happen to have any memorabilia of Henlys in London? My car was delivered new on April 4, 1975 by Henlys, 88 Piccadilly, London. As per Google Maps there’s nothing left of it.

Good luck


75 XJ6L 4.2 auto (UK spec)

(Paul Breen pay palled it) #20

Hi Jochen, I definitely think that is often the problem - compounded by difficult access to fix. I rewrapped my hot air line and it helped the AED come off more rapidly. You can buy kits but are expensive. Her mechanic at the time (now it’s me) sent her to Henlys with a list: along with the AED she arrived back with two rear disc rotors and other parts. All at a time when hand luggage was not weighed. Sorry, have nothing from Henlys now. At the time they were quite interested at the thought of a petite Australian in her twenties with a list of parts for her own XJ6. Paul