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Out for a run in 6 today - and found that the car is running 'lumpy'. It started fine, but once warmed up it ran what I can only describe as 'lumpy' until revs. get up to about 3,000 rpm then all fine and goes well. My first thought was petrol supply (had a new Bosch pump fitted about 300 miles ago) but ruled this out given how well the car ran when more petrol (higher revs) required.

Any ideas?

Ernest

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Look at your plugs too, might have a misfire from a dirty plug. Also check your injector lines for pulsing.

Gareth

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Thanks Peter and Gareth

It looks like: check points and plugs then, if still poor running, check the P.I. system. I would be relived but disappointed if it

was plugs or points as a new set of each was fitted during a recent service carried out be a respected TR garage (about 50miles ago).

Thanks again

 Ernest

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1 hour ago, Ernest said:

Thanks Peter and Gareth

It looks like: check points and plugs then, if still poor running, check the P.I. system. I would be relived but disappointed if it

was plugs or points as a new set of each was fitted during a recent service carried out be a respected TR garage (about 50miles ago).

Thanks again

 Ernest

Ernest,  Points can wear that fast, especially plastic ones if lacking a small smear of molygrease on the cam. Peter

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Has it ever run smoothly since fitting the Bosch pump?

They are quite demanding of their power supply in my experience, I had a marginal Alternator and my idle and pick up improved significantly when I upgraded it.

Thanks

Sean

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Thanks Peter

I will check points for wear and if greased.

Sean

The Bosch pump was fitted by Maidstone Sports Cars (this was not the garage who did the recent service noted above) and the car has run realy well since then (approx 300 miles). Indeed the guys at Maidstone Sports said that as a driver this 6 was about the best they had driven.

Thanks

Ernest

 

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I would suspect throttle balance, check to see when the throttle cable is lifted, do all three arms lift at the same time?

This tool would be very useful, but prices do vary for the same item at different places.

https://www.amazon.co.uk/Deluxe-Carburetor-Airflow-Latest-Rage/dp/B00CMC57R0

John

 

Edited by John L
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Hi John

That's an interesting suggestion - I have checked the plugs and all clean and set correctly -  and no points (electronic ignition).

So I am thinking something to do with P.I. system, which would be beyond my technical ability, but I can at least check the throttle cable as

you suggest.

Thanks

Ernest

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Hi Ernest,

             You could try this, with the engine running remove each injector in turn from the throttle bodies and check that each gives a fine cone of petrol sprayed from the tip (care needed here, into a small jam jar or similar), any injector with failed flow, dribbling, or large droplets will be the culprit, and sometimes a bit of gentle persuasion can bring a failing injector back to life, ie tapping or gently pulling out the fine tip with a pair of small pliers, simple job you just need a 1/2"AF socket or spanner to remove the three keeper plates then the injectors just pull out.

Cheers Rob  

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Hi Rob

Thanks for this suggestion - I am wary about tinkering with the P.I. unit but I will consider the action you suggest.

I was thinking of taking the car to Sanspeed in Bexleyheath to let see if they can identify, and hopefully resolve, the problem.

They have tuned a 4a for me in the past and the improvement was marked.

Thanks again

Ernest

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On 6/16/2021 at 11:08 AM, John L said:

I would suspect throttle balance, check to see when the throttle cable is lifted, do all three arms lift at the same time?

This tool would be very useful, but prices do vary for the same item at different places.

https://www.amazon.co.uk/Deluxe-Carburetor-Airflow-Latest-Rage/dp/B00CMC57R0

John

 

+1 and check that the black injector pipework has no air in them and enquire bleeding by checking them for pulsing.

Bruce.

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If the injectors are quite old then for a very modest cost they can be refurbished and will perform well for many years thereafter

mine were refurbished in 2013 by Neil Fergussen and have been faultless ever since.

steve

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On 6/18/2021 at 6:45 PM, Ernest said:

Hi Rob

Thanks for this suggestion - I am wary about tinkering with the P.I. unit but I will consider the action you suggest.

I was thinking of taking the car to Sanspeed in Bexleyheath to let see if they can identify, and hopefully resolve, the problem.

They have tuned a 4a for me in the past and the improvement was marked.

Thanks again

Ernest

Unfortunately clearing injectors is a must know for PI owners. It will happen occasionally that the car will be running on 5 cylinders. It is usually 2 or 5 and can be ascertained by feeling each injector tube in turn and the faulty one will have very weak or no pulses through the tube.

Bleeding isn't too hard as described above. Just be careful not to damage the injector tip. It may take a short while to clear but be gentle with the injector tip.

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Thanks Bruce, Steve, John

For these further sugestions - I took it out agan  yesterday and problem continues - bit weird as it idles fine and once above 2000 rpm it goes as good as ever.

The lumpy ruinning happens between about 800-2000 rpm.

Ernest

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That now sounds a bit like the lean spike that the metering unit has if its set too lean.  As the metering unit doesn't have an accelerator pump, that's what happens.

A small adjustment to the metering unit to make it a bit richer would fix it.

Find a club member to make an adjustment, where are you?

John

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I ran a Triumph 2.5Pi saloon for around 25 years and during that time became very familiar with all aspects of the Pi system, the car was and Auto and as you can imagine it needed a smooth tick over and pick-up from idle, I found that if the throttle bodies were very slightly mis-aligned then the transition from 800 to 2000 would be, shall we say, uncomfortable .... Triumph produced a jig for correctly mounting the TBs, but using a solid straight edge across the airbox spigots works, although it's somewhat fiddly to get right, ........ it seems to me that if the TB spindles are not directly in line then the inter connecting levers and screws can't cope and give a slightly different opening to each TB as they move and consequently a slightly different airflow through each, ...... if all else fails then worth a check. 

Cheers Rob          

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Thanks John and Rob

I am really wary about tinkering with the P.I. I live in Hayes, Bromley, south London (about 3 miles from Biggin Hill airport) and would appreciate if a club member living nearby would be prepared to adjust the metering unit - very happpy to make a donation to a charity if this can happen.

Best Wishes

Ernest

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1 hour ago, Ernest said:

Thanks John and Rob

I am really wary about tinkering with the P.I. I live in Hayes, Bromley, south London (about 3 miles from Biggin Hill airport) and would appreciate if a club member living nearby would be prepared to adjust the metering unit - very happpy to make a donation to a charity if this can happen.

Best Wishes

Ernest

As your in London, take it to Enginuity https://www.enginuity.co.uk/

Stuart.

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Hi Stuart

Thanks for the suggestion, I understand that they have a good reputation.

I don't know how well you know London but the journey from here to west London would be awful - I would think that the car would be running between idle and 2000 rmp for most of the run, so pretty uncomfortable for the TR and for me re. 'lumpy running' for pretty much the whole 2-3 hour journey.

I was down in Cornwal for a week recently (Polruan nr Fowey) and the roads were lovely and clear, if a little narow in places! I envy you having access to these driving conditions

Best Wishes

Ernest

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1 hour ago, Ernest said:

Hi Stuart

Thanks for the suggestion, I understand that they have a good reputation.

I don't know how well you know London but the journey from here to west London would be awful - I would think that the car would be running between idle and 2000 rmp for most of the run, so pretty uncomfortable for the TR and for me re. 'lumpy running' for pretty much the whole 2-3 hour journey.

I was down in Cornwal for a week recently (Polruan nr Fowey) and the roads were lovely and clear, if a little narow in places! I envy you having access to these driving conditions

Best Wishes

Ernest

Yes I know London very well so do understand but Im sure if you asked they would happily collect it which would be a lot easier.

Next time your down come and say hello

Stuart.

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Hi Stuart

 

Yes of couse...... I did not think of using a car transport - I guess my mind is focused on obtaiing more local help.

It would be lovely to come along to your garage, and to view any current restorations, so thanks for the invite - I will bring

half a dozen of the lovely saffron buns to share with you and your staff!

Best Wishes

Ernest

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