Hello all. A quick and basic question on the automatic choke.
Am I correct in assuming that if the wires to the solenoid are disconnected then that means the choke is not being activated?
Just want to confirm that no power = no auto choke and not vice-a-versa (ie no power means choke is engaged)
Thanks

 

No power means no choke.
If there IS power, that means that the solenoid is open, that lets atmospheric pressure to flow into the engine, and along with atmospheric pressure, extra fuel will flow into the combustion chambers from the float bowl from the front carburetor nearest the radiator.

One wire is fed 12 volts with the key on, the other makes the circuit to ground through the otter switch.

Most will replace the putzy otter switch with a manual one inside the car.

 

Thanks Jeff. You say "No power means to choke"
Is that the way you meant to type it or is there a typo there ie should it read "No power means no choke"?.
Mine is currently disconnected?

 

Sorry, Type-O
No power means NO choke.

I've corrected it.

 

Thanks mate - much appreciated

 

A lot of people have changed the operation of the Auto choke to a manual operation.

Auto means when the engine is cold the otter switch is closed allowing an earth. When the ignition is on power is constantly being fed to the choke solenoid and with the otter switch creating the earth the solenoid is open and the choke works. As the engine gets hot the otter switch which is a Bi Metal type switch opens cutting off the earth and the solenoid closes and the choke ceases to function. There is still a live feed going to the solenoid but because there is no earth it does not work.

Manual is just a switch which allows electrical operation of the choke whilst sat in the cabin. Without spending a lot of money or by changing the carburettors can you change them to a manual cable operated style choke.

To bypass the Auto function and to create a manual choke there are two ways.

Bypass the Otter switch by replacing the earth wire from the solenoid to one that goes back to the dash where a switch allows you to create an earth. When the switch is on creating an earth the choke is on. With the switch off there is no earth and the choke is off. The problem with this method is if you forget to switch off the earth the choke stays on and the engine will run very rich.

The second way and the way I have it, is to have a switch on the dash which interrupts the live feed to the solenoid whilst leaving the Otter switch in place to create the earth. So when the switch is on power is fed to the solenoid and the choke works. This can be switched off at any time turning off the power using the dash switch but if you were to forget to switch off the power then the Otter switch will kick in breaking the earth when the engine becomes hot and the choke will switch off.

This I feel is the better method as the main problem with the Otter switch is as they get older they fail to function correctly and can remain constantly on creating the earth which allows power to work the solenoid meaning the choke is constantly on.

 

Hi Jag folks ,
I have been having some issues with overfueling on my series one XJ6 .My auto choke seems to disengage at temperature as the hissing sound stops and the needle returns to the open position.Is there a way to lean out how much fuel it injects while activated?

Ben Uri , Cape Town RSA

 

See post 2 here ~ Cass covers well. Configurations have changed over the years but the same principle applies as in attached Word document with Thermo SU Carbs & needle setting. Also covered on the Burlen website that took over Skinners Union carburetters. See SU Thermo section.

https://www.jaguarforums.com/forum/m...g-carb-264596/

https://burlen.co.uk/

 

so by default, the solenoid is spring loaded to the closed position, consequently cutting off manifold access to extra fuel. hmmm...good to know. it was the first question that entered my mind when i thought about putting in a manual choke switch (not that it would be too difficult to find out). i often wondered, as it could have been set up in the opposite way. thanks for asking that question.

 

Buy this A 5 book. Not expensive.

 

My old 1959 Mark 1 3.4l overdrive had a choke interruptor switch fitted by my Dad in 1964 (plate under radio). Still going strong last year if the ads for 3076 AD is anything to go by.