XJ40 ( XJ81 ) 1986 - 1994

Only starts when Aussie Sun heats up.

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Old 02-07-2018, 01:50 AM
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Default Only starts when Aussie Sun heats up.

Hi everyone; I am just new here.
I have got an 89 Jaguar Sovereign that I have ‘fixed up’ and Registered because it is
immaculate inside, and has only done 155,000 kilometres.
But my BIG problem is that it will only start when the Queensland Sun has heated the car up;
then it will start for the rest of that day.
Put a new fuel filter in the line. And the injector rail has only clean fuel (no rust, water, or impurities).
My professional Jaguar expert has no idea why it only starts in the heat of the Sun.
I would be very grateful for any assistance.
Tony
 
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Old 02-07-2018, 02:59 AM
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The coolant temperature sensor is responsible for cold-start enrichment - it's the sensor that tells the computer that the car is cold. If it fails or the harness/plug is damaged/dirty then no cold start enrichment takes place, so she'll be hard to start from cold.
 
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Old 02-07-2018, 08:57 AM
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Originally Posted by Antony
Hi everyone; I am just new here. .....
Welcome to the forum Tony,

I've moved your question from a Non Starting thread to a new one of your own. I think Lawrence is on the right track in post #2.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham
 
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Old 02-08-2018, 03:58 AM
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Default Thank you Lawrence.

Originally Posted by Lawrence
The coolant temperature sensor is responsible for cold-start enrichment - it's the sensor that tells the computer that the car is cold. If it fails or the harness/plug is damaged/dirty then no cold start enrichment takes place, so she'll be hard to start from cold.
Thank you Lawrence. I copied your message to my professional Jaguar expert here in Brisbane Australia.
He said the sensor kicks in below 6 degrees Centigrade (which is very rare in Coastal Queensland). He said disconnection will probably flood the engine; but for me to try it anyway. Which I will (I will try anything to get the Jaguar started...~because all my restoration is useless if the car won’t go..).
 
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Old 02-08-2018, 09:17 AM
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Originally Posted by Antony Hamilton
Thank you Lawrence. I copied your message to my professional Jaguar expert here in Brisbane Australia.
He said the sensor kicks in below 6 degrees Centigrade (which is very rare in Coastal Queensland). He said disconnection will probably flood the engine; but for me to try it anyway.

Hi Antony,

Your professional Jaguar expert must be thinking of some other sensor in some other car, because in the XJ40 the coolant temperature sensor (CTS) is a continuously-variable thermistor (temperature-sensitive resistor) whose resistance varies over most of the climatic temperature range available on Earth.

Here's the info on the CTS from the Engine Management Systems manual:




You and your mechanic can download the EMS manual at the link below. It is for the 4.0L cars, but the details are essentially the same for the 3.6L cars, and the same CTS part number applies to the entire XJ40 range:

Jaguar AJ6 4.0L Engine Management System/OBDI Diagnostic Guide

You can easily test the operation of the CTS by testing the resistance across its terminals when the engine is cold (at ambient temperature) and when it is hot, and comparing the readings to the chart. A more precise test is to remove the CTS and check its resistance with the probe in a glass of ice water (0C/32F) and in a pot of boiling water (100C/212F).

Cheers,

Don
 
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Old 02-11-2018, 06:58 AM
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Originally Posted by Don B

Hi Antony,

Your professional Jaguar expert must be thinking of some other sensor in some other car, because in the XJ40 the coolant temperature sensor (CTS) is a continuously-variable thermistor (temperature-sensitive resistor) whose resistance varies over most of the climatic temperature range available on Earth.

Here's the info on the CTS from the Engine Management Systems manual:




You and your mechanic can download the EMS manual at the link below. It is for the 4.0L cars, but the details are essentially the same for the 3.6L cars, and the same CTS part number applies to the entire XJ40 range:

Jaguar AJ6 4.0L Engine Management System/OBDI Diagnostic Guide

You can easily test the operation of the CTS by testing the resistance across its terminals when the engine is cold (at ambient temperature) and when it is hot, and comparing the readings to the chart. A more precise test is to remove the CTS and check its resistance with the probe in a glass of ice water (0C/32F) and in a pot of boiling water (100C/212F).

Cheers,

Don
Dear Don; thank you very much. I will examine what you have sent me.
It sure will be good to get the Jaguar starting at will. It is nighttime here now;
and there is a electrical storm outside.
My first Jaguar (which has already been claimed by my 33 year old son);
has been a series of challenges since I drove it home.
Then there was the bad fumes leak, from the plastic bung which holds the
petrol guage sender float. Then there was the unsatisfactory brakes; and the endless banging & clanging of shockies that had lost their foam rubber inserts.
But still, the fact that I cannot start it at will; is a bigger concern for me now, than were those previous challenges.
have already fixed.
 
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