1968 240 Jag runs perfectly for 30 mins then dies

[FalconWood]

I have a problem I can't sort with my 68 240 Jaguar.
After running perfectly for 30 minutes the red ignition light comes on and when I slow down the engine cuts out. When I try to start if it sounds as if it has run out of petrol - ignition system tries but can't start. Leave it for an hour to cool and it starts first time then runs 30 minutes and process repeats.

It has petrol. I changed the Dynamo. Help please on diagnosis and solution would be appreciated!

[FalconWood]

Thanks William. I have not in my time of ownership of 4 years changed those electrical components so I will try that. Even if it doesn't fix it it will do it no harm!

[FalconWood]

Thanks William. I have not in my time of ownership of 4 years changed those electrical components so I will try that. Even if it doesn't fix it it will do it no harm!

[FalconWood]

Penelope Stopit said:

What a strange response to so many posters that have given so much input

k

I think your referring to my second "Thank you William" post that just appeared on my screen for no apparent reason when I logged in the other day.!! Don't know how that happened I am about as reliable of PH as my Jag is getting me around.

Everyone has been helpful so thank you all.

I checked the distributor and it was a real mess. Spoke to a very helpful gent who sent me a red rotar arm to replace my black one. Cleaned up the all the contact points. Fitted new red rotar arm. Blew out all the rubbish in distributor cap etc and refitted. Car had not been started for 5 days from my first request for help and battery was completely dead. Used my battery pack and started first time. Left trickle charge on battery recharge and after further 3 days battery charged to 13.4 volts. Started first time but red ignition light on all the time. Took car to garage and they now testing the battery. Think I am getting closer to a solution.

Thank you all for your help. It is much appreciated. I am sure this is an electrical issue and will keep you posted.

[FalconWood]

Penelope Stopit said:

FalconWood said:

Penelope Stopit said:

What a strange response to so many posters that have given so much input

k

I think your referring to my second "Thank you William" post that just appeared on my screen for no apparent reason when I logged in the other day.!! Don't know how that happened I am about as reliable of PH as my Jag is getting me around.

Everyone has been helpful so thank you all.

I checked the distributor and it was a real mess. Spoke to a very helpful gent who sent me a red rotar arm to replace my black one. Cleaned up the all the contact points. Fitted new red rotar arm. Blew out all the rubbish in distributor cap etc and refitted. Car had not been started for 5 days from my first request for help and battery was completely dead. Used my battery pack and started first time. Left trickle charge on battery recharge and after further 3 days battery charged to 13.4 volts. Started first time but red ignition light on all the time. Took car to garage and they now testing the battery. Think I am getting closer to a solution.

Thank you all for your help. It is much appreciated. I am sure this is an electrical issue and will keep you posted.

OK. there have been many time wasters posting here recently
If the battery light is staying on there is a 99% chance there will be a dynamo or control box fault, the problem is that many garages/people dont have the experience in setting up an RB 106 or RB 340 control box, your car will most likely have an RB 106 but it could have been upgraded to an RB 340
It is a ongoing problem that new dynamos are fitted to vehicles yet the control boxes are not set up correctly
A faulty dynamo will damage a good control box, a faulty control box will damage a good dynamo
All of the above is going on an ignition light staying on brightly

If the ignition light is glowing dimly the problem can be caused by a volt drop anywhere along the ignition warning light circuit and is often to be found at the ignition supply to the warning light being less than battery voltage when the engine is running

You would be wise in replacing the dynamo and control box if one of them is the cause of the present fault and do make sure that the dynamo is polarised before running it for the first time

Your Jaguar is a stunning car

Thanks Penelope

The battery has now been changed and the garage had indeed said that the dynamo is not passing out charge! This was a very recently supplied dynamo from a specialist but they did not change the control box. Your note suggest that this is something we should do at the same time to prevent the one breaking the other (?). The said out will take a couple of weeks to sort the dynamo issue out so I will get the control box identified and have that changed too.

Thanks again for the advice.

[FalconWood]

Penelope Stopit said:

FalconWood said:

Penelope Stopit said:

FalconWood said:

Penelope Stopit said:

What a strange response to so many posters that have given so much input

k

I think your referring to my second "Thank you William" post that just appeared on my screen for no apparent reason when I logged in the other day.!! Don't know how that happened I am about as reliable of PH as my Jag is getting me around.

Everyone has been helpful so thank you all.

I checked the distributor and it was a real mess. Spoke to a very helpful gent who sent me a red rotar arm to replace my black one. Cleaned up the all the contact points. Fitted new red rotar arm. Blew out all the rubbish in distributor cap etc and refitted. Car had not been started for 5 days from my first request for help and battery was completely dead. Used my battery pack and started first time. Left trickle charge on battery recharge and after further 3 days battery charged to 13.4 volts. Started first time but red ignition light on all the time. Took car to garage and they now testing the battery. Think I am getting closer to a solution.

Thank you all for your help. It is much appreciated. I am sure this is an electrical issue and will keep you posted.

OK. there have been many time wasters posting here recently
If the battery light is staying on there is a 99% chance there will be a dynamo or control box fault, the problem is that many garages/people dont have the experience in setting up an RB 106 or RB 340 control box, your car will most likely have an RB 106 but it could have been upgraded to an RB 340
It is a ongoing problem that new dynamos are fitted to vehicles yet the control boxes are not set up correctly
A faulty dynamo will damage a good control box, a faulty control box will damage a good dynamo
All of the above is going on an ignition light staying on brightly

If the ignition light is glowing dimly the problem can be caused by a volt drop anywhere along the ignition warning light circuit and is often to be found at the ignition supply to the warning light being less than battery voltage when the engine is running

You would be wise in replacing the dynamo and control box if one of them is the cause of the present fault and do make sure that the dynamo is polarised before running it for the first time

Your Jaguar is a stunning car

Thanks Penelope

The battery has now been changed and the garage had indeed said that the dynamo is not passing out charge! This was a very recently supplied dynamo from a specialist but they did not change the control box. Your note suggest that this is something we should do at the same time to prevent the one breaking the other (?). The said out will take a couple of weeks to sort the dynamo issue out so I will get the control box identified and have that changed too.

Thanks again for the advice.

Very good. If you dismantle the dynamo that has just failed you may well find that the armature commutator has thrown its solder, you can tell by looking at the inside of the dynamo barrel at the commutator end, you will see a ring of silver
There is something else that I forgot to mention earlier and it is another critical one. The control box relies on a good earth connection to regulate the voltage and that earth connection is not made through the body of the control box, the control box has its own earth terminal that an earth wire connects to, someone must locate where that earth wire bolts to the body and clean it up plus tighten and grease it, a new earth lead can always be added to minimise the prospect of it being a problem in the future
Should the earth at the conrol box be bad, over-voltage occurs and a new dynamo will throw its commutator solder within seconds of running it due to it getting extremely hot, its that critical

Lovely car

Hi Penelope

The car came home today from the garage with new battery, new dynamo and new control box. They also rechecked the earth on the battery and the control box. I haven't driven it yet but they say the red light has gone and the dynamo is passing out power etc to the car. I will take it out tomorrow to see how it runs and let you know.

Thanks you for your help to you and all the other contributors!!!!

[FalconWood]

The car is back! Took it out for a 40 minute drive and no recurrence of the issue! The garage provided new battery, new dynamo and new control box. After Penelope's advice they renewed all the earths (a very weak one form the Control Box they said) They believe the dynamo was passing 17 volts to the battery at 1700 revs and may have cooked the battery. The new set up is passing between 13 and 14 volts which is better. I renewed the rotor arm to a red one as advised by one of the contributors from the Distributor Doctor and all seems well.

Thank you all for your rapid and accurate responses to my problem. I really appreciate it and feel more confident that the Jag will behave properly now. Thank you!!