Jaguar Repair: 85 jag sj6, coolant temperature, web bot

Question
i have a 85 jag sj6 hard to start when cold after it warm up ron fine i have change the cold start valve ang relay what els should i look for i dont kno/ the wiring for the relay where it staet        please help. this is the first time to see your web bot i a/m proud of u// and i hope god bless u// for your service and time. thanks so much. jim

Answer
Hi James,
The cold start valve/injector is not operated by a relay. It is operated by a thermotime switch in the coolant rail. It is usually the forward most switch and it the largest of the switches in the rail. It is called a "thermo-time" switch because it will cut off the operation of the cold start valve if the coolant temperature is up or if the time that the valve is open is too long.

It is simple to test if it is a lack of fuel causing the no start when cold by spraying starter fluid into the intake when the engine is cold.

If it starts right up then you should check the operation of the cold start valve. It is nothing but a solenoid with two connections. You can remove the plug connector and connect a power wire on one side and just touch the other pin with a ground and you will hear and feel it "Click". This just tells you that the solenoid is working, it does not tell you that fuel is being sprayed.

To test the thermotime switch remove the plug and check both pins on the switch (engine cold) with an ohm meter and both should show as a ground.

To test the wiring remove BOTH plugs off of the thermotime switch and off of the cold start valve and remove all of the small wires off of ONE side of the coil and have someone hit the starter while you test the both sockets with a test light and you should find that each socket will have a hot wire while the key is in the "Start" position. This tests the power side of the wiring.

In these tests you should be able to find out if the cold start system is working.
Howard