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Running badly - any ideas?


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Have you changed polarity from positive earth to negative earth?

If so, you need to swap connections on the coil in order to get a decent spark at the plugs.

According to Tony Tranter in Haynes "Automobile Electrical Manual", ignition systems are designed to have negative polarity at the centre electrode and if reversed can be up to 40% less efficient.
Coils for both Positive and Negative earth vehicles were produced, but who knows if anyone has changed a coil for the wrong type in the history of older vehicles, so it is wise to check polarity of the spark (see below for testing polarity using a lead pencil).
With early coils, swapping the CB and SW leads will switch polarity of the spark.  Later coils use + and - but the requirements are the same.
To test the spark direction with a lead pencil, interpose the writing tip of a lead pencil between the spark plug top stud and the HT lead, leaving a small gap either side of the pencil tip.  If the polarity is correct, a flare between the pencil and the spark plug will be seen (if the flare is between the pencil tip and the HT lead, then the polarity is reversed).

Ian Cornish

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Ian thanks for your thoughts. I haven’t changed polarity. Thing is the engine was running fine, now it isn’t. Have just tried separate battery on the coil but it’s still dead. Plan now is to take the distributor off the 2 and see if that works. But I just don’t see that working because there is spark there so how could there be anything wrong with the distributor? I’m convinced there are two faults just coincidentally at the same time. JJC

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4 hours ago, Quicksilver said:

Coming late to, just read this tread,

but if you have a TR2 by hand, why did you change "things" one by one  at the time and check of it works on the TR 2. 

(just a thought)

Marcel.

 

Well yes, that’s pretty much what’s happened and I’m none the wiser. It won’t even fire on Easy Start now. JJC

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On 2/5/2019 at 4:10 PM, Quicksilver said:

And the TR2 is starting well with the parts of the TR4 ? or did you have now two cars that did not start?

Marcel

 

That’s what I said this morning. I’ve now got two cars unable to move under their own steam. On the bright side though there’s still one more. Not only that none of them are venturing out until all the salt has washed off the roads.

Today, the recalcitrant beast decided to speak. Not much, just one backfire, but more than it’s done for ages. I’ve put the complete distributor off the 2 onto the dead 4. And yes, just one backfire. I know it’s not much but I’ll take what I can get after all this time. Life after death, almost.

on the more technical side the volts on the coil are up around 11 volts. That implies a leak path in the original distributor from the 4. (That was down around 7).

I just might be getting closer. On the other hand it still doesn’t go.

JJC

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14 hours ago, JJC said:

 

on the more technical side the volts on the coil are up around 11 volts. That implies a leak path in the original distributor from the 4. (That was down around 7).

 

Not a leak, but a high resistance in series with the coil. Is the small earth lead to the points in good condition? Easy enough to check by adding a second one. Should be easy enough to find where the voltage drop is; leave one lead of your meter connected to the chassis/body and measure the voltage at the battery, then the solenoid, then the fusebox, and so on.

Pete

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Completely off the wall, but was prepping a 4A exhaust manifold this morning and noted that the manifold gasket can be fitted 90 degrees out - it will go on perfectly but pretty much blocks off all the exhaust flow, so that would have a pretty big effect I would have thought and be difficult to spot

Not sure if you did anything to the manifold, but just a thought

Cheers

Rich 

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Turns out it was the plugs. As a last gasp thought I took the plugs out of the 2 and used those. It fired up straight away. So that was two sets of new Champions that failed for whatever reason. Now I have to get all the bits back on the right cars and chuck the failed plugs in the bin.

Thanks for all your suggestions 

JJC

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1 hour ago, JJC said:

Turns out it was the plugs. As a last gasp thought I took the plugs out of the 2 and used those. It fired up straight away. So that was two sets of new Champions that failed for whatever reason. Now I have to get all the bits back on the right cars and chuck the failed plugs in the bin.

Thanks for all your suggestions 

JJC

Hi JJC,

     I had the same problem about two years ago with NGK plugs.  Slow speed hard throttle usually in 2nd and it would miss something chronic.

I swapped over to Champion L87 from Moss and these have lasted two years.

The NGK's would last about 1000 miles (1 month) and then go phut.

 

Sorry I didn't put that forward to you.

 

Roger

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15 hours ago, RogerH said:

Hi JJC,

     I had the same problem about two years ago with NGK plugs.  Slow speed hard throttle usually in 2nd and it would miss something chronic.

I swapped over to Champion L87 from Moss and these have lasted two years.

The NGK's would last about 1000 miles (1 month) and then go phut.

 

Sorry I didn't put that forward to you.

 

Roger

I did mention a problem with NGK`s earlier that didnt like getting wet when new several posts ago.

Stuart.

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I've only ever used NGK BP6HS or BP7HS plugs for over 30 years now and have never had one failure. I wonder if your problem was due to fakes Roger, there are some about apparently.

Tim

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Like Tim, I've been using BP7HS since 1993 - no problems.

I purchase occasional replacement sets from the supplier in Somerset who fitted them in the first place (when the car was re-built there) and whom I trust.

Ian Cornish

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I believe most plugs are produced under local license. The problem may lay with the certification or lack thereof OR with the type of certification. That doesn't make them "fake", just of  different quality standards (local, regional, international). I suppose one way of mitigating the risks of having to deal with troublesome products is to look for international standards (ISO).  I never had any problem with NGK plugs produced locally to me though.

WhatsApp Image 2019-02-15 at 17.18.16.jpeg

Edited by Geko
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27 minutes ago, Geko said:

I believe most plugs are produced under local license. The problem may lay with the certification or lack thereof OR with the type of certification. That doesn't make them "fake", just of  different quality standards (local, regional, international). I suppose one way of mitigating the risks of having to deal with troublesome products is to look for international standards (ISO).  I never had any problem with NGK plugs produced locally to me though.

WhatsApp Image 2019-02-15 at 17.18.16.jpeg

That will be because yours are produced to OE standards from Japan, the problem ones are Chinese knock off ones.

Stuart.

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So these should be ok then. Put the new plugs in the 2 and it’s back running as it should. The 4 now runs but still has problems. I think I’m losing volts on the coil so will track that down. The other problem is that it sort of peters out. As if it forgets what it’s doing. That might be a bit more difficult to find. JJC

4170AEDF-FB20-4093-A591-8B9072800A34.jpeg

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I have just found this thread. It looks like you have a lot of patience. At least it is the winter, but still cold in the garage.

A long time ago I heard that the employees at NGK  were stealing the boxes and making counterfeit plugs and selling them on the side.

Last year I changed to Iridium plugs and my starting really improved when cold. I also had the carburettors cleaned with carb cleaner  by a local sports car garage

Try Iridium from the Green Spark Plug co.

Good luck, Richard and B.

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3 hours ago, Richardtr3a said:

 

A long time ago I heard that the employees at NGK  were stealing the boxes and making counterfeit plugs and selling them on the side

Good luck, Richard and B.

That’s a bit of a depressing thought.

Thinking again about the volts across the coil when cranking the starter is it so surprising they drop? If anyone has nothing to do measure the volts whilst cranking and see what they are. Should be the same for all the 4 pot engines. Thanks! JJC

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