Hi All, our '72 has an SU AED auto choke. We’re going on a long trip at the end of the week and I will pack my spare AED - but it begs the question in the title. Expect that I might have to close off the carburetter air/fuel ports (that accept the hoses from the AED) and try to start on the main carburetters - maybe with some Aerostart? Happy for any thoughts or experience. Regards, Paul
I don’t know which carbies you have (HD, HS, HIF, probably HS?) but if there is a jet adjusting screw you could simply lower the jet a few turns when starting/warming up, then reset the jets to their correct position. The manual choke versions do just that, except conveniently from inside the cabin.
If you can’t adjust the mixture, or it might even be worth trying this first.take with you a small weed killer container or similar that you can pressurise. Put petrol in it.
If AED fails, remove air filter spray atomised fuel into carb intakes, quickly get someone to turn engine over whist you hold something over carbs in takes to further riches the mixture. This usually works but make sure you spray only into intakes.
Engines get addicted to easystart or similar so I wouldn’t recommend use of it!!!
Did not know that, but very interesting. Addiction requires a memory…the engine “knows” that it’s used starting fluid in the past. What’s the physical substrate for that memory? In other words, what would one look for in a disassembled engine to determine whether or not it was addicted?
Hi Robert
Very hard to detect but believe me it’s true!
Especially Diesel engines.
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Calling the AED an ‘autochoke’ does it an injustice, Paul…
Its a carb in its own right, enriching fuelling, admittedly a ‘choke’ function, and adding extra air to increase idle, a ‘fast cam’ function - both aiding easy cold start and idle. Both functions gradually closing down as engine temp increase, admittedly ‘automatic’. This leaves the main carb free to only run a hot engine - which simplifies their task…
The problem with your question is that the AED may fail in different ways - cold starting will usually be affected. But a failed AED may also cause running problems with the engine warmed up - but both situation may equally be caused by other faults, unrelated to the AED.
The ‘best’ way to deal with a failed AED is indeed as you expect; blocking both fuel inlet and overflow drain by hose clamping - and close the hot air delivery pipe. This indeed leaves you starting on the main carbs - which are tuned for hot running. There is no way to adjust the main carbs for both cold start and hot running - slight pedal and ‘start gas’, or petrol, as suggested by Nigelplug is about as quick as it gets…or whatever else takes your fancy with a recalcitrant engine…
When started, the cold engine will be a bit hesitant before warming up. But do you have any indication that the AED could fail…?
Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks to all for your thoughts. Both my AEDs function properly (one was “new in box” 25 years ago - not used). I have no reason to believe they won’t operate but we will be a bit remote on some of the journey - so just good planning! I know “auto choke” is an inadequate description - they are a very elegant piece of analogue machinery! Apparently designed to start and run a car at -30 Celsius with very short “wait” time. My car has the standard HS style carbs fitted to a 1972 model. Similar but larger to the 13/4" units I had on the Dolomite Sprint of my youth - choke “pulled down” on the main jets as described to enrichen at start. Regards, Paul
Mechanical addiction to Ether? Yes, according to some, including my son, it can happen.
The theory is that ether is utterly bereft of any lubricating quality, and as such enhances wear at start up.
Worn engines are harder to start. Poor compression.
Lesser ability to inhale a combustible mixture. Ether
“lights up” easier. Engine fires.
In practice, while a healhy engine may need a boost, a squirt of gas into the intake will fire it.
Aka as priming, an ancient technique.
Yeah, I’m guilty, my stubborn lawn mower is “addicted”. But, once it get’s it’s hit, it fires up and runs great enough to mow the pastures. They are now over grown, but far to wet to mow…
Carl
1 Like
Thanks Carl. Makes perfect sense.
You’ve made perfect sense to me Carl.
We also have an old Ford major 1950s tractor at our workshops, only gets started up when the grass is growing ! We have a mowing deck running through the PTO.
Unless it gets its fix of Easystart it doesn’t want to play! But starts fine once it’s warm of course!
operating?
Breen60 Paul Breen
January 10
Thanks to all for your thoughts. Both my AEDs function properly (one was
“new in box” 25 years ago - not used). I have no reason to believe they
won’t operate but we will be a bit remote on some of the journey - so just
good planning! I know “auto choke” is an inadequate description - they are a
very elegant piece of analogue machinery! Apparently designed to start and
run a car at -30 Celsius with very short “wait” time. My car has the
standard HS style carbs fitted to a 1972 model. Similar but larger to the
13/4" units I had on the Dolomite Sprint of my youth - choke “pulled down”
on the main jets as described to enrichen at start. Regards, Paul
I wish my '74 XJ had AED… Sadly enough it’s a manual choke that works too well. haha. on a cold day I’ve got to monkey with it to get the engine to start, which equates to barely on once the engine starts, then monkey with the throttle to keep the Kitty running. Just one of the reasons why I miss my S-III 
me
Paul,
sorry to chime in so late! - Excursion: I organized the new infrastructure of jag-lovers in a way to resemble the former xjdigest as much as possible. In fact I do receive an e-mail headed “[Jag-lovers forum] Summary for January 17” (etc.) every day. Yet, only today’s summary contained Mike’s most recent post on this thread. All the posts before including the initial post must have beenn lost in transition somehow. Is this a general problem? Any experience with this? End of excursion.
The enrichment device being what it is I think you don’t have to fear any “sudden death”, at least not with the AED that was used on HS8 carbs of SII cars. Earlier systems may differ - Frank will know all the dirty details … Malfunction of the AED usually consists in the bimetallic spring not closing fully any more after the engine has warmed up. Sometimes this is caused by fatigue of the bimetallic strip, sometimes the insulation of the air pipe leading from the exhaust side around the block to the AED gets lost, causing the bimetallic strip not to sense “hot” sufficiently. OTOH I never heard of an AED failing to enrich. This doesn’t exclude “normal” failure modes for carbs such as sinking floats, flooding, sticking needle etc. But if it works now there is no reason why it wouldn’t work on your journey.
If the AED should become disfunctional for whatever reason I found that from 10°C on the car will start without it and some patience and playing with the loud pedal.
Mike, if your AED has been replaced by a manual choke chances are that you only received the popular conversion kit replacing the automatic bimetallic strip part control of the auxiliary carb, but not by a “real” choke as common on HS carbs. You recognize it by the neat brass cam sitting on top operating two pistons (air and fuel) for the lower part. My car has the same conversion and used to make me very unhappy with its cold starting and running properties. Only after some years I was bothered enough to check the setup of the manual choke conversion against the installation instructions. I found the gap over one of the pistons and the cams to be out of specs, corrected it and have enjoyed reliable starting and an unexciting cold running period ever since. Not very astonishing, but tenths of millimeters matter.
Good luck
Jochen
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the S2 engine I am about to fit has the manual choke HS8 conversion to replace the AED, and its adjustable for both throttle and relative needle depth
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a previous Jag motor was minus the AED, but had a plastic lawnmower on/off valve fitted instead!
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engine start spray often mainly ether, and hence washes all oil from bore walls, supposedly causing wear,
but so long as rarely used, doubtful of claimed harm…or how would LPG engines last
Hello All, we’re now in Hobart Tasmania. Have covered 1260 miles and on Thursday we head back to Sydney. Our XJ is running well, just the hint of a blow ex the rear exhaust gasket - this will last until we get home. AED is fine. Highway/Freeway running mostly - mileage has been good! If I changed anything it would be the axle ratio - could be a bit taller to get the best out of second gear (BW12) and drop cruising rpm. More later with some pictures. Paul
Jochen could you please send me the settings of the manual choke you mention…
I bought one XJ6 -S2 with it installed and it has the same problem you describe.
Thanks a lot.
Eugenio.
Hi Eugenio,
try to include the mounting instructions that came with my manual conversion kit. The settings are included.
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Thanks a lot Jochen is the same conversion kit so I guess it will work.
Thanks again for your quick support.
Eugenio.
Gee, that is an ingenious bit of kit! Was not aware it worked over the existing AED. Might ask my second hand guys if they have one. Could fit one to my spare. Paul
Indeed, Paul, the common term “Manual choke conversion kit” is misleading, although just about every kit I’ve seen on the market so far is the same. While our list member Keith Turner has come up with a true manual choke conversion, the kits on the market leave the third enrichment carb in place and only swap out the automatic control of this carb effected by the bimetallic strip in the black plastic top section with a manually operated camshaft and two cams as seen in the second picture. Looks good and works well, if the cams are positioned correctly.
Sure enough, comfortwise it won’t come close to a well working AED, but with the reportedly limited life time of an AED, its considerable costs of replacement and the relatively low significance of cold start comfort on my car I don’t regret the PO’s decision to install the kit. As mentioned earlier, getting the specs correctly is essential.
BTW, while the kits seem to be pretty much the same all over the place, prices vary considerably and follow the similarly inexplicable price changes of the replacement AEDs. Currently, the price at SNG Barratt is at approx. 120 UKP for the conversion kit as opposed to approx. 300 UKP for the AED. If you find a used one, even better. There’s nothing in the kit on the carb that really can go bad with age or use and you can make up a manual operation cable from just about anything suitable.
Best regards
Jochen
75 XJ6L 4.2 auto (UK spec)