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Rough tick over and missing


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Hi all

i would welcome any comments on this problem that’s driving me nuts,my 72 has had a rough running/miss since I bought it but my friend and I have been trying to sort it for weeks.It starts but ticks over rough and when the revs go up a miss is clearly evident along with some popping and banging ,the things we have checked out using the brown manual is fuel supply including the injection system and all the timing set up situations.Now here’s the thing,we can’t get a spark when shorting out no3 lead at all,the sparks on the other leads aren’t that good either,the leads distributor cap,rotar arm,points and plugs are all new!! I am thinking coil it looks new but as I don’t know much about coils should it be a ballasted coil I can’t find a ballast any where as it does get hot,the other thing that’s throwing me is why can’t I get a continuity reading when I carry out a basic test with my meter ( like nothing at all!!),they are new carbon type leads,so am I doing something wrong?I should add the car has only done just under 40,000 miles and is totally standard 

thanks in anticipation

nige

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My first action with a miss or rough running is to replace the coil and condensor. The condensor first, it is cheap and easy to do.

I carry a spare condensor and coil in my cars. They fail too regularly.

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Does it run and rev the same with no. 3 disconnected? 

Is the rotor arm a decent one like the one from distributor Dr? 

Gareth

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I hear you lads,but why am I not getting any form of resistance reading when I test the lead (off the car)shouldn’t I get some thing as the p/o fitted carbon fibre type leads?or am I missing something with my limited knowledge!the car wasn’t running well when we acquired it

nige

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1 hour ago, nigelcurry said:

I hear you lads,but why am I not getting any form of resistance reading when I test the lead (off the car)shouldn’t I get some thing as the p/o fitted carbon fibre type leads?or am I missing something with my limited knowledge!the car wasn’t running well when we acquired it

nige

You need to set the multimeter for fairly high resistance with carbon cored  leads:

https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwirqKP11cPvAhXDILcAHfmoCVoQFjACegQIAhAD&url=https%3A%2F%2Fwww.instructables.com%2FHow-to-Test-a-Spark-Plug-Wire%2F%23%3A~%3Atext%3DFor%20copper%20core%20wires%2C%20the%2Cto%207000%20ohms%20per%20foot.&usg=AOvVaw2VDLL3Ca5KjbFfWUuq-YY2

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A ‘72 CP car shouldnt have a ballast resistor iirc, only the later CR cars had one.

hth

ps, whereabouts are you located ?

Edited by Steves_TR6
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7 hours ago, Mike C said:

My CP has a ballast resistor. As far as I know it's a later ceramic replacement of the original.

So does mine. I have disconnected it but left it there.

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On 3/22/2021 at 10:19 AM, Mike C said:

Whose spark plugs leads are fitted to your car? I had this problem and difficult starting when hot. It was traced back to the new Sparkrite leads where some of the spark plug terminations were not in contact with the top of the spark plug. I pulled the terminations down on the 3 faulty leads to the bottom of the hood covers and the problem was gone????. Apparently this problem is very common on Sparkrite leads as per MGB owners! Another QA problem sorted!

Bruce. 

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Are you absolutely certain it is missing?

Badly adjusted butterflies can give symptoms astonishing like a missfire, particularly the CR series with popping and a seemingly screwed up mixture, evident on closed and partial open throtte yet at full throttle runs better.

 

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On 3/22/2021 at 4:55 PM, Steves_TR6 said:

A ‘72 CP car shouldnt have a ballast resistor iirc, only the later CR cars had one.

hth

ps, whereabouts are you located ?

No TR's has ever had a ballast resistor only CR types had a resistive wire in the harness with a pink jacket??

Bruce.

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2 hours ago, astontr6 said:

No TR's has ever had a ballast resistor only CR types had a resistive wire in the harness with a pink jacket??

Bruce.

That was my understanding.

Ie no TR before the CR Tr6 had the ballast arrangement to reduce voltage to the coil when running/boost coil power for cranking

the CR6 and onwards did have ballast ‘resistors’ either as resistive wire in the loom or external 

steve

Edited by Steves_TR6
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