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4.5 - Auxillary Starting Carburetor Modification ( Alastair Reynolds,  )

Location of new switch and relay

The original circuit before modification

Picturegram of original circuit

Modified circuit

Modified Picturegram




Temperature Sensor


The ASC can cause flooding and can come on unexpectedly. A number of Jag owners
wonder at the crude operation of the Jaguar Auxiliary Starting Carburetor (ASC) from the 1960's.
It is meant to cut out automatically when the engine gets hot but invariably stays on too long
or comes on again after a short stop causing flooding when restarting. There are some expensive
modifications on the market but I have a solution that cures most of the problems with the addition
of a push button and a horn relay. I have had this installed on my 1966 S Type for some years now
with satisfactory performance.

This page suggests the addition on a push switch under the dashboard coupled to a latching relay.
Once the button is pressed the ASC comes on till either the temperature rises or the ignition is switched
off. The advantages of such a system are listed below:
* No obvious additional switch visible
* Will not come on till you press the button
* Automatically cuts off when the ignition switch is switched off
* Can be disengaged by flicking the ignition switch without stopping the engine

The following is a pictorial description of the modification. I would suggest the modification is
carried out using Automotive Lucar connectors properly soldered or crimped. These parts can
be obtained from a local car accessory shop including the SPST relay.

Here is a complete set of images to help you with the modification.

The author takes no responsibility for any damage caused by this modification.
You do this procedure at your own risk. No warranties are given or implied.


sepbar.jpg (3094 bytes)

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