Automatic choke

[jaguar&mg]

Whilst fiddling with idle speeds and generally meddling to try to solve some gearbox chatter I have managed to put the automatic choke onto a mixture so rich that the engine can barely cope without spluttering and stalling. At the back there is virtually black liquid from the exhaust until the choke has switched off (which is often a while, and presumably why a manual override would be helpful one day).

I can't re-track the setting. I thought I knew how to adjust the mixture of the choke without affecting the engine's mixture when warm, but it seems that I'm not getting that right. Would anyone, please, be willing to illustrate exactly which screw should be turned to adjust the strength of the choke? Its previous setting was ideal for the summer months (barely any choke needed) but this is currently too strong for any season!

[Norton]

Hi. The service manual describes this procedure. See photos.
Service manual can be downloaded from this forum: S-Type Documents.

When I got my car the otter switch ( temp sensing swtch on water rail just behind thermostat, whitch normally deenergize solenoid when engine heats up ) was disconnected and choke system ( Auxiliary Starting Carburetor ) solenoid permanently earthed. A switch was fitted under dash to energize / deenergize ASC. I changed the otter switch and reconnected it to earth. AST works as it should. But I still had the switch to turn it off. Just for the sake of it I took it a bit further..
Installed a three position toggle switch and two relays. Now I have: off, auto and on. I leave it normally in «auto», but can turn it on or off at will. Needed some electric wiring but a simple installation. Also installed a small led warning light that illuminates whenever ASC is energized. You can have details if you want.
Harald.

[cass3958]

I have a similar system to Harald on my AED. I have a switch on the dash (an extra rear window heater switch) which allows power to the AED. It uses the integral red light in the switch to show the AED is power on. I then rely on the Otter switch to automatically switch the AED off but can also switch the AED off in the summer with the power switch. In th ewinter I was having a problem in that the Otter switch was turning off to early which meant the AED was not powering up two min from the house trying to pull away up a hill from a junction. Temporally I have fitted a straight earth connection from the otter switch to the inner wing so I am by passing the otter switch turning the AED off. When I get time I will alter the setting of the otter switch to stay on longer but I like the three position switch idea Harald has got.
So with your problem the nut 13 in the diagram is the one you need to adjust. From memory down is to weaken and up is to enrich but you can take hold of the top of the needle 10 and pull this up of down to get the engine running just right and then adjust the nut 13 to hold it in the correct position.
If you are having problems with the car being too rich and stalling on you you can just pull either of the wires off the AED or the one wire on the Otter switch and this will turn the AED off.

[jaguar&mg]

Hi. The service manual describes this procedure. See photos.
Service manual can be downloaded from this forum: S-Type Documents.

Very helpful: thank you. I now have proper control of my automatic choke and it is set particularly well at the moment (!).

When I got my car the otter switch ( temp sensing swtch on water rail just behind thermostat, whitch normally deenergize solenoid when engine heats up ) was disconnected and choke system ( Auxiliary Starting Carburetor ) solenoid permanently earthed. A switch was fitted under dash to energize / deenergize ASC. I changed the otter switch and reconnected it to earth. AST works as it should. But I still had the switch to turn it off. Just for the sake of it I took it a bit further..
Installed a three position toggle switch and two relays. Now I have: off, auto and on. I leave it normally in «auto», but can turn it on or off at will. Needed some electric wiring but a simple installation. Also installed a small led warning light that illuminates whenever ASC is energized. You can have details if you want.
Harald.

I think this needs to be my longer-term solution. Details would be very helpful: thank you.

[Norton]

Hi.
I have drawn the modification into the wire diagram, see photos. The content of the black square ( photo 2 ) on green wire to the choke solenoid, I have tried to draw on top right corner of wire diagram ( photo 1 ). I don’t know how to draw a 3 pos toggle switch properly but have tried.. Middle position is off. Pushing switch down powers upper terminal, pushing up powers lower terminal.

I have used two changing relays, but the RH ( on drawing ) don’t have to be.

Toggle switch in middle position ( off ) solenoid is powered throug relaxed LH relay.
Switch down powers LH relay and solenoid receives no power. Choke off.
Switch up powers RH relay and solenoid is earthed regardless of otterswitch. Choke on.
A small led warning light also wired in, it will light up whenever solenoid is powered either by otterswitch or toggle switch.

I have placed the relays on a beam under dash left of steering collumn, but switch and warning light on a small alu plate under dash right of steering. LHD car.

Two wires need to be pulled from engine bay to the relays. Switch is powered from a terminal at fusebox throug an additinal fuse of much lower value, 3A. As my choke already was powered from a switch under dash I needed only one additional wire from the earth side of choke solenoid.

( As can be seen I have also stop lights powered by a relay, was recommended on this forum )

If unclear, feel free to ask.

Rgds Harald.

[jaguar&mg]

This is very helpful, thank you. I am about to see if, with the assistance of a technical friend (I am not technical) I can install some sort of manual system like this.

It is timely as the choke is not coming on at all in this UK heat, yet the engine clearly needs some help to get going. Starting at the moment takes quite a while, with many stutters and half-attempts along the way, which seems ridiculous in the unusually hot weather!

[John Quilter]

This all seems a bit complicated. On my car the Otter switch turned the AED off too soon and the car would stall at stop signs. Rather than fiddle with the Otter switch adjustment I simply ran an additional wire from the switch terminal to a double pole single throw toggle throw switch under the dash. The other side of the switch went to ground. The other function of the switch was to activate a warning lamp. I can now flip on the AED at will momentarily when at stop signs or stop lamps or if climbing a hill when the engine is still cold.

[JCS]

Jaguar&mg

“………..It is timely as the choke is not coming on at all in this UK heat, yet the engine clearly needs some help to get going. Starting at the moment takes quite a while, with many stutters and half-attempts along the way, which seems ridiculous in the unusually hot weather!.....”

Looking through the existing threads, on this site and others, there does not appear to be any comment regarding voltage drop when starting.
By the very nature of the AEC unit it is powered up initially when the starter motor is used. With the limited checks I have made I notice that the AEC solenoid often does not “hold in” under starter motor cranking. In short the starter is taking the available amps. This is noticeable when two batteries are connected in series when the additional cranking amps are available and the voltage drop at the AEC solenoid…..and indeed the ignition coil is boosted. In the double battery scenario, there are no splutters or coughs.

This has led me to consider trying to locate a heavy duty 9 volt / 10 volt solenoid for the AEC or having the original one re-strung.

Any comment ?

Norman

[cass3958]

Never had that problem Norman. My car starts first time with the choke on but I agree with who ever it was that stated the Otter switch was turning the AED off too quickly so there were times I would drive two miles down the road to a set of traffic lights with a steep hill beyond and as my AED had been cut off by the Otter switch I could hardly get going away from the lights let alone up the hill. (Being an Auto there is no chance of revving the engine and slipping the clutch). I have now rigged a switch that allows me to power the AED but have also by passed the Otter switch so the choke is controlled purely by the switch and gives me the ability to switch the AED on momentarily to get rolling away from the lights or up the hill before switching it back off when the engine revs are high enough.

[jaguar&mg]

Looking through the existing threads, on this site and others, there does not appear to be any comment regarding voltage drop when starting.
By the very nature of the AEC unit it is powered up initially when the starter motor is used.

Norman

I am interested by this as I am not very good technically and have struggled with the switch for manual choke.

So a few options, then, to get my S-Type running properly on 'cold' start. Thank you.