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kcsun

Car won't start, electrical

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Hi all, went to the garage to start the car and it won't start!

It is a 73 PI CR engine with a Luminition system which I fitted 5 years ago and has worked perfectly until now. I turn the ignition on and there is 12v at the coil, I then start churning the starter motor and the voltage at the coil drops to about 9 - 9.5v. The engine does not fire, when I release the ignition switch the engine fires on the release and tries to start???? If it fires successfully the engine runs OK. I do not think there is any spark while the starter is churning but is a bit difficult to see as I have only one pair of arms!! I am assuming it then sparks as the ignition switch is released

any ideas??

kc

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Cranking dropping battery voltage so providing poor/no spark stop cranking engine on starter battery voltage increases providing enough power for  a spark, engine tries to fire on residual motion from starter ?

battery needs charging or is US that’s my guess as a starter anyway (no pun intended)

edit do CR series cars use ballast resistors if so might it be an issue there 

 

Edited by Graham

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Kc

Had the same issue earlier this year. Problem traced to failing battery. New battery fitted problem solved.

Suggest  you try jump starting from a known good battery just to check.

Good Luck 

Brian

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Sounds like the ignition switch is faulty.....had exactly the same problem several times!

Regards Mark

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I'd look at the ballast resistor and it's wiring. I made a gadget out of stuff in the shed incorporating a PVC tube with a wire from the distributor lead  to earth and an adjustable  spark gap at the bottom. The tube keeps light out and lets me see the spark. The adjustable gap let's me measure it's strength. 

But you might have to check for a spark at night if you suspect the ballast resistor.

100_6687_resized.jpg

Edited by Mike C
Tried to reduce photo size.

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  • Thanks for your replies, will check the battery after work tomorrow, i will charge it up and connect my "jump pack" to the battery to add a bit of boost and see what happens
  • I was thinking about the ballast resistor, there is a 12v link wire from the starter motor shown on the wiring diagram, but I do not know where to find the resistor or the "connector block" shown in the wiring diagrams

kc

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The resistor is actually resistive wire and is part of the loom, so you can't really see it.  The ballast resistor isn't doing much when cranking as the wire from the starter is supposed to be giving the full 12v to the coil.  Since you only measure 9-and-a-bit either that link has a bad connection (which might include the switch although that apparently is operating the starter solenoid OK) or your battery is low on charge as Graham says.  

 

Edited by RobH

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My 1969 CP's ballast resistor is a white ceramic thing on the rear passenger side of the engine bay if this helps.

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12 hours ago, Graham said:

Cranking dropping battery voltage so providing poor/no spark stop cranking engine on starter battery voltage increases providing enough power for  a spark, engine tries to fire on residual motion from starter ?

battery needs charging or is US that’s my guess as a starter anyway (no pun intended)

edit do CR series cars use ballast resistors if so might it be an issue there 

 

CR cars have a resistive wire which does the same thing as ballast resistor. I got rid of that system years ago by by-passing that wire. If you do this you have to change the coil as well as it is a 6 volt coil which is meant to give a bigger spark when starting???. I would change the coil to a 12 volt type and do a temp lash up power supply to the coil and see what happens! This can easierly be done taking the SW power from the fuse box! I did this for another TR owner this year when he have trouble with that resistive wire!

Bruce.

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9 hours ago, Mike C said:

My 1969 CP's ballast resistor is a white ceramic thing on the rear passenger side of the engine bay if this helps.

That will be an aftermarket alteration as thats not original.Jaguars of the period had the same thing.

Stuart.

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Hi KC,

if it tries to start after you disengage the 'starting' position on the switch then the ballast resistance wire (Red/White)    looks as if it is OK.

Check out the White/Yellow  starting wire that should give 12V to you coil with the starter motor spinning. This may be open circuit.

http://www.advanceautowire.com/tr2506.pdf

 

Roger

 

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I’m with Roger, good thought.

Waldi

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Update for you

As Roger said I checked the wire from the starter motor, which fell apart when I touched it, remade the connection ---- and no difference. So last night I put my large battery charger on the battery (up till then I had only been using my small trickle charger (which always lit up to say the battery was fully charged!!) anyway went out to garage this evening, connected the battery and whoosh -- started first time

Battery obviously was never fully charged as Graham and Brian suggested

Will check everything more fully tomorrow but think it is cured (note to self - never trust the green light on a trickle charger, no it wasn't a C-Tek)

kc

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On 10/25/2019 at 9:18 PM, RogerH said:

Hi KC,

if it tries to start after you disengage the 'starting' position on the switch then the ballast resistance wire (Red/White)    looks as if it is OK.

Check out the White/Yellow  starting wire that should give 12V to you coil with the starter motor spinning. This may be open circuit.

http://www.advanceautowire.com/tr2506.pdf

 

Roger

 

PM me KC if you need a CR wiring diagram.  The AAW website doesn't have it

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Or use the diagrams in Rogers link.

The ballast resist wire is shown however in the bottom four diagrams in Rogers link.

Regards,

Waldi

edit:

During starting the YW wire provides current to the coil, it will be a bit less than 12V because you are cranking.

Once you let loose the ignition switch/button, the YW wire will no longer be “fed” directly. Now the (reduced) voltage is provided by the WR ballast wire.

Edited by Waldi

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21 hours ago, Waldi said:

Or use the diagrams in Rogers link.

That's the AAW link that has every single wiring diagram except for for CR cars

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On 10/24/2019 at 11:24 AM, kcsun said:

Hi all, went to the garage to start the car and it won't start!

 I turn the ignition on and there is 12v at the coil

kc

If KC has 12v at the coil when not trying to start, then there is no ballast system!

Graeme

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4 hours ago, matttnz said:

That's the AAW link that has every single wiring diagram except for for CR cars

Yes, but the relevant part is shown there, so they could be used to investigate this issue.

Regards,

Waldi

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Not completely because of the ballast wire and connections.  Basic principle of course is similar I agree, but chasing connections down off those AAW diagrams can be exasperating at times.

]

 

image.png

Edited by matttnz
Personal muppetry

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