nigelcurry Posted March 21, 2021 Report Share Posted March 21, 2021 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 Quote Link to post Share on other sites
Mike C Posted March 21, 2021 Report Share Posted March 21, 2021 If you cut the engine after the miss do the plugs look wet or sooty? My car has a separate ballast but I believe some TR's have the ballast built into the LT supply wire. Quote Link to post Share on other sites
John McCormack Posted March 22, 2021 Report Share Posted March 22, 2021 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. Quote Link to post Share on other sites
nigelcurry Posted March 22, 2021 Author Report Share Posted March 22, 2021 Certainly sooty but not wet Mike,(plugs 1and2)less so Quote Link to post Share on other sites
Mike C Posted March 22, 2021 Report Share Posted March 22, 2021 Sooty is either misfiring or rich mixture. I've tried many different plugs over the years and the only one that fires flawlessly regardless of mixture condition is the NGK BUR 6ET. Quote Link to post Share on other sites
Mk2 Chopper Posted March 22, 2021 Report Share Posted March 22, 2021 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 Quote Link to post Share on other sites
nigelcurry Posted March 22, 2021 Author Report Share Posted March 22, 2021 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 Quote Link to post Share on other sites
Mike C Posted March 22, 2021 Report Share Posted March 22, 2021 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 Quote Link to post Share on other sites
nigelcurry Posted March 22, 2021 Author Report Share Posted March 22, 2021 With you on that one Mike i have just ordered new leads/cap/coil/plugs/points from Moss i will get to the bottom of this one way or another thanks for the advice lads stay safe almost there nige Quote Link to post Share on other sites
Steves_TR6 Posted March 22, 2021 Report Share Posted March 22, 2021 (edited) A ‘72 CP car shouldnt have a ballast resistor iirc, only the later CR cars had one. hth ps, whereabouts are you located ? Edited March 22, 2021 by Steves_TR6 Quote Link to post Share on other sites
Mike C Posted March 22, 2021 Report Share Posted March 22, 2021 My CP has a ballast resistor. As far as I know it's a later ceramic replacement of the original. Quote Link to post Share on other sites
John McCormack Posted March 23, 2021 Report Share Posted March 23, 2021 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. Quote Link to post Share on other sites
Kevo_6 Posted March 23, 2021 Report Share Posted March 23, 2021 My 72 CP doesn’t have a ballast resistor. Quote Link to post Share on other sites
nigelcurry Posted March 23, 2021 Author Report Share Posted March 23, 2021 Hi all just fitted all the above and it was the leads,I spoke to Tony at Moss and he told me as you rightly said Kev there is no ballast resistor on 72 cp.Anyhoo car runs tons better now thanks all nige Quote Link to post Share on other sites
astontr6 Posted March 23, 2021 Report Share Posted March 23, 2021 On 3/22/2021 at 10:19 AM, Mike C said: 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 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. Quote Link to post Share on other sites
Andy Moltu Posted March 24, 2021 Report Share Posted March 24, 2021 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. Quote Link to post Share on other sites
astontr6 Posted March 24, 2021 Report Share Posted March 24, 2021 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. Quote Link to post Share on other sites
Steves_TR6 Posted March 24, 2021 Report Share Posted March 24, 2021 (edited) 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 March 24, 2021 by Steves_TR6 Quote Link to post Share on other sites
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