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Rough pick up after idling


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Have been out in the 6 today and noticed that when pulling away from a junction, after the car has been idling for a short while, it would only pick up on 5 cylinders. After a the revs go past 2k and the car has travelled 20m or so everything is back to normal. Engine does not seem particularly lumpy on idle. Plugs and plug leads are new and the car is fitted with a Petronix Ignitor system.  The car is also a bit of a pain to start after it has been standing for a while. I am thinking it might be a dodgy injector that is fouling a plug. Anyone have any other thoughts?

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There is a different topic running at the moment regarding TR6 coils. One post from Andy Moltu states; "CRs had a 1.5ohm coil working at 8-9v with the ballast resistor built into the feed wire." I noticed yesterday that the Petronix instruction leaflet says the live feed to the system should be taken from the input side of the balance resistor. It looks like whoever fitted the system to my car did not realise that there was an integral balance resistor in the loom. They have taken the feed off the coil, i.e. from the output side of the balance resistor.

Does anyone know if this is important?

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If, as you say, the makers have expressly specified not to do that in their leaflet - I guess it is important. The effect will be that the unit only has 8v supply when running rather than 12v.  During starting it will get the full 12v as the ballast is shorted out, so starting should not be affected. 

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I'd assume that if the Pertronix only got 8V when running and it was supposed to get 12 V it would affect the ignition. I have a Pertronix I installed 15 years ago, it's given no problems since but I can remember going to great lengths to make sure it was installed strictly in accordance with the manufacturer's instructions- this took a bit of checking because  systems with external ballast resistors, like mine , are comparatively rare outside of classic cars. 

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Richard,

Have you still got the same fuel in the tank when the car presumably went into the garage in Autumn 2019? With lockdown there are many cars with  some very old fuel in the tank and it is not a good wine and does not improve with age, many of the volatile fractions of petrol which evaporate easily and start the ignition burn may have gone walkabout leaving the strange aroma of old petrol. 

OK the problem could be many things but don't spend too much money on parts until the fuel has been used and replaced.

Alan

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Thanks Guys.

It is a 1975 CR with fuel injection, fitted with a 6V coil and ballast resister. The car has done just over 200 miles since I bought it in January (the equivalent of a third of the total mileage over the preceding 5 years). The tank was filled up about 5 weeks ago with 98 RON unleaded, it has been converted to run unleaded. Also has a Bosch pump conversion. I am trying to use as much fuel as possible at the moment as I noticed the fuel filter has a lot of crud in it. The filter needs cleaning or replacing but I need to empty the tank first.

Today I rewired in the Petronix unit correctly and just started the car up. It started relatively easily on the second turn of the key. But it had only been run yesterday, so probably still plenty of fuel in the injector lines. I had the bonnet open when I started the car and noticed a little bit of blowback on one or two cylinders when blipping the throttle. That stopped as the engine warmed. Tick over is nice and smooth at around 600 rpm and it is running on all six. But there is still the slightest hesitation when you press the accelerator.

So the next step is to replace the coil and the vacuum hose from the manifold to MU. The hose is not in terrible condition but is past its best. I will also check the timing.

I did also swap one of the injectors out as two refurbished ones came with the car. The little filter on the inlet was not in straight and the injector rattles something terrible when you shake it. So I am guessing the seals have gone and that is the reason for the poor starting when the car has not been used for a while.

So I have a question. What is the best source of refurbished injectors? I can see one seller on eBay offering an exchange set for £70 + P&P https://www.ebay.co.uk/itm/TR6-5-LUCAS-PETROL-INJECTORS-six-EXCHANGE/143609431359 Anyone have any recommendations?

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Hi Richard, that is Neil Ferguson and he is also on this forum as well. Most recommend him as do I. He is very approachable and will service and recondition your own equipment at very reasonable rates. If you need his contact details, please let me know.

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2 hours ago, Kevo_6 said:

Hi Richard, that is Neil Ferguson and he is also on this forum as well. Most recommend him as do I. He is very approachable and will service and recondition your own equipment at very reasonable rates. If you need his contact details, please let me know.

Thanks Kev,

I had seen Neil's name crop up before but had not made the connection with the eBay seller.

Have been in touch with Neil this afternoon and my injectors are packed up and ready to post off to him.

Regards,

Richard

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On 5/28/2020 at 9:43 AM, Richard Green 54 said:

There is a different topic running at the moment regarding TR6 coils. One post from Andy Moltu states; "CRs had a 1.5ohm coil working at 8-9v with the ballast resistor built into the feed wire." I noticed yesterday that the Petronix instruction leaflet says the live feed to the system should be taken from the input side of the balance resistor. It looks like whoever fitted the system to my car did not realise that there was an integral balance resistor in the loom. They have taken the feed off the coil, i.e. from the output side of the balance resistor.

Does anyone know if this is important?

There is no resistor in any TR ignition wiring unless someone has added one? BL post 1972 cars added a resistive wire which does the same job! To take this out would mean dismantling the harness? Not a got idea in my view! The other way is to by- pass this wire completely by a piggy back terminal on a s/wed wire at the fuse box. This is what I did years ago and have had no trouble. Pertronix also advise doing this. Also I would check that you do  have a 12 volt coil fitted as BL fitted 6volt coils when they went to using resistive wire .The idea being that the resistive wire supplies 12v on start up to a 6v coil and you get a bigger spark then after awhile the resistive wire brings the voltage down to about 7 volts so as not to burn out the coil,

Bruce. 

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2 minutes ago, astontr6 said:

There is no resistor in any TR ignition wiring unless someone has added one? BL post 1972 cars added a resistive wire which does the same job! To take this out would mean dismantling the harness? Not a got idea in my view! The other way is to by- pass this wire completely by a piggy back terminal on a s/wed wire at the fuse box. This is what I did years ago and have had no trouble. Pertronix also advise doing this. Also I would check that you do  have a 12 volt coil fitted as BL fitted 6volt coils when they went to using resistive wire .The idea being that the resistive wire supplies 12v on start up to a 6v coil and you get a bigger spark then after awhile the resistive wire brings the voltage down to about 7 volts so as not to burn out the coil,

Bruce. 

I looked at the wiring diagram before rewiring the Petronix unit yesterday and spotted the resistive wire reference. That still seems to be in-situ and I believe the car also still has its original 6V coil. The problem was that whoever originally fitted the Petronix system had not looked at the wiring diagram and/or realised that the coil was 6V.

I have now taken a 12V feed from the input to the inertia switch. It is an ignition switched feed and it was much easier to piggy back at that point than trying to link into the fusebox. I have also fitted a 15A in-line fuse into the new feed as an additional precaution. I might drop this down to 10A at some point.

I am now confident that the Petronix unit is wired as per the manufacturers instructions.

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18 minutes ago, Richard Green 54 said:

I looked at the wiring diagram before rewiring the Petronix unit yesterday and spotted the resistive wire reference. That still seems to be in-situ and I believe the car also still has its original 6V coil. The problem was that whoever originally fitted the Petronix system had not looked at the wiring diagram and/or realised that the coil was 6V.

I have now taken a 12V feed from the input to the inertia switch. It is an ignition switched feed and it was much easier to piggy back at that point than trying to link into the fusebox. I have also fitted a 15A in-line fuse into the new feed as an additional precaution. I might drop this down to 10A at some point.

I am now confident that the Petronix unit is wired as per the manufacturers instructions.

Hi Richard,

Have you checked your pump for volt drop? The original cars suffered from this? I am not certain that the way you have wired your coil will not affect the voltage to the pump? As you have a late TR RHD 1976? you should have the later larger wire size cable fitted if you are still on the original harness?

Bruce.

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1 hour ago, astontr6 said:

Hi Richard,

Have you checked your pump for volt drop? The original cars suffered from this? I am not certain that the way you have wired your coil will not affect the voltage to the pump? As you have a late TR RHD 1976? you should have the later larger wire size cable fitted if you are still on the original harness?

Bruce.

Hi Bruce,

Thanks for the warning. I will have a think about that but as everything comes off the same terminal on the ignition switch it might be a bit academic. Also the car has a Bosch conversion that runs off a relay. I will need to work through the wiring and check to see where the inertial switch fits into the revised circuitry. If it still sits in the main pump feed it might be an issue. But if it sits in the relay activation circuit then it isn't.

Why are these things never as straight forward as they should be? Never mind, my injectors went off for exchange this morning. So I have a few days to diddle around with a multi-meter while I await the return of the replacements.

Richard

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