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TR6 Backfires and cuts out.


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My US spec TR6 (Carbs, Not P.I. ) developed a fault recently.

When warm it will sporadically backfire, lose power and stop. Aftercooling down it runs as if there was nothing wrong. This can happen afer 1 mile or 20 miles.

Yesterday after 1/2 mile it backfired, ran lumpy for a couple of minutes then was perfectly fine.

It's really difficult to identify the cause when the symptoms are not always present.

I have changed fuel, fuel filter, fuel pump, distributor cap, rotor arm, points, plugs, and coil to no avail. Ordered new condensor to fit next weekend.

Any more suggestions ? It would be great not to have a low loader follow me everywhere !

 

IMG-20210501-WA0006.jpg

Edited by Kenj
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Forgot to mention, before I moved back from the US  2 years ago I fitted a new gas tank and had the carbs rebuilt by Glenn's British car repair St Petersburg FL

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Are the advance weights properly attached and moving  correctly in the distributor? 

Can't think what could cause it to come and go like that with all the things you've done already?

Gareth

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Certainly sounds as though it might be an ignition problem but you seem to have changed most of those bits. Fingers crossed it is the condenser but they tend to go wrong in a permanent way rather than intermittent.

 Have you checked the wire between the dizzy and the coil?  if there is an intermittent connection there it might do this sort of thing.  The wire isn't supported so can fail due to vibration - check where it enters the connectors at each end.  Also the flexible earth wire in the distributor between the moving plate and the body.  Neither would explain the cooling-down symptom though. 

 

 

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Sticking float/needle valve fuel starvation?

Had the same issue many years ago which was random and would happen at the worst possible times! Just because they have been rebuilt doesn't rule it out.

Andy

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Also might be worth checking your petrol tank breather, if it's blocked then you may get similar symptoms - ask me how I know.

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I would favour fuel problems. Sticking needle jet on the floats are my first thought,

Fuel shortages give weak mixture and high spark plug temperature and  backfiring. As rwest above check tank breather.

No mention of the  carbs do they have diaphragms that split (CD175's) etc?

Alan

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I had these symptoms (starts and drives well until it gets warm then backfires and stops and refuses to start - after a 10 minutes or so it starts right up, drives ok until it gets warm again and then stops).

In my case, the problem started after I had changed the points.  I swapped them back to my old points and the problem vanished.  On inspection of the problem points ( brand new from dizzie doc), it seems that the spring loses spring tension when hot and the points stay open... most bizarre.  Reported this back to dizzie doc and he sent me a replacement set.  
 

good luck.

dave

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Almost guarantee the condensor. 95% of problems are ignition and condensors fail frequently, usually when hot. The symptoms are as you describe.

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Dear KenJ, 

This is interesting, When you do get to the root of it, could you share please what the cause is as I have same setup or type of car, and who knows, one day I (or others) suffer from this :-)

Richard

 

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I had this problem on another classic I own. It would run perfect for 10 miles or so then start missing, back firing etc and then stop, no spark. tried every thing, new plugs, points, capicitor, leads, cap, rotors, coil, etc carb rebuild. In the end I swopped the complete distributor and its run perfectly ever since.

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If the disy has two vacuum capsules disconnect the vac retrad one from the carb and set static timing to cA 18 BTDC, assuming the head has stcok compression ratio.

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On 5/24/2021 at 8:57 AM, John McCormack said:

Almost guarantee the condensor. 95% of problems are ignition and condensors fail frequently, usually when hot. The symptoms are as you describe.

+1

known this several times

Roy

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I vote for condenser too!

evil little ba$tards they are, cause you to buy lots of dearer and unnecessary parts while they play ‘now i work now i dont’ with your engine

i once spent weeks and many £££ trying to track down an intermittent problem on  and old v8 boat engine - condnser!

Good luck !

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Can't wait for the OP to come back and let us know if it cured the problem. 

Gareth

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1 hour ago, John L said:

Fit an Accuspark and do away with the condenser:rolleyes:

Are these nice and reliable John?

I've always resisted changing from points as I feel it's something that encourages maintenance, but I'm wondering if I had a condenser issue with my recent problem. Of course I could always go to Distributor Doctor for a decent replacement. Then again I like the idea of the constant dwell you get with electronic. 

Gareth

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Not all electronic systems give constant dwell Gareth.  Many of the cheaper ones do not, and those that do usually require a special type of matching coil. 

Edited by RobH
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11 minutes ago, RobH said:

Not all electronic systems give constant dwell Gareth.  Many of the cheaper ones do not, and those that do usually require a special type of matching coil. 

Thanks Rob, I need to do some research...

Gareth

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Points are easy to repair and to carry spares but they are pretty agricultural when it comes to delivering a powerful, consistent spark at the right time every time.

I have a Lumenition in my TR6. The car had one in it which failed last year. It had been in the car for decades so they are reliable and I got another one to slip straight in. No points or condensor, improved spark and timing, better idle, power and economy. It is a single point of failure and they are a bit expensive. Unfortunately a PO modified the distributor by removing the pin the points pivot on so I have no spare. 

I repaired the broken connection on the old one and put it into my daily driver TR2. Again it improved performance and easy to carry spare points and condensor in the boot,

I used to have an Accuspark in that TR2. It failed and a 2nd one also failed. Talking with the supplier the Accuspark don't like generators as they charge at 16-17 volts and the Accuspark is limited to 14.5 v or thereabouts.

Edited by John McCormack
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2 hours ago, John McCormack said:

Points are easy to repair and to carry spares but they are pretty agricultural when it comes to delivering a powerful, consistent spark at the right time every time.

I have a Lumenition in my TR6. The car had one in it which failed last year. It had been in the car for decades so they are reliable and I got another one to slip straight in. No points or condensor, improved spark and timing, better idle, power and economy. It is a single point of failure and they are a bit expensive. Unfortunately a PO modified the distributor by removing the pin the points pivot on so I have no spare. 

I repaired the broken connection on the old one and put it into my daily driver TR2. Again it improved performance and easy to carry spare points and condensor in the boot,

I used to have an Accuspark in that TR2. It failed and a 2nd one also failed. Talking with the supplier the Accuspark don't like generators as they charge at 16-17 volts and the Accuspark is limited to 14.5 v or thereabouts.

Maybe I should try some electronic ignition and see what difference it might make. 

But which one to go for? The Luminition lasted well for you, so that's a plus, the other one that's talked about is Pertronix, the igniter 2 having the fabled constant dwell. 

Sorry I feel I've muscled in on the thread, but hopefully it'll help the original poster. 

Gareth

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I have accuspark and have also had an aldon ignitor. All have worked well. One died in service (but suspect it may have had some welding pulses through it when I was doing the rear deck). Accusparks are cheap enough for me to keep a spare in the tool kit..

Tim

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1 hour ago, Tim D. said:

I have accuspark and have also had an aldon ignitor. All have worked well. One died in service (but suspect it may have had some welding pulses through it when I was doing the rear deck). Accusparks are cheap enough for me to keep a spare in the tool kit..

Tim

That's a fair point on the cost, though something is telling me buy cheap buy twice!

Gareth

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