Jump to content

One tailpipe smoking


Recommended Posts

I've recently finished complete re-build and successfully got the MOT, but the engine isn't running right, feels like it's running on 5 and idle is far from smooth...

injectors are all spraying fine and decent spark (new plugs) on all. Engine seems to run more smoothly as revs increase which made me think it might be a timing issue but I've tinkered with timing between 4 and 12 degs (static) with no improvement (12 seems better). It's a 1973 engine (re-built by Gary Bailey), injection unit re-built by Prestige.

One clue which I can't crack is that the left hand tail pipe smokes far more than the right (which doesn't smoke much at all) also holding palms at both pipes the LH exhaust seems cooler; which makes me think one of the cylinders isn't firing properly.

Grateful any thoughts ?

Thanks.

Mac.

 

Link to post
Share on other sites

Mac,

Need more info:

What colour smoke? black ( too rich ) or blue (oil burning) or white but not steam ( glycol burning)

You have sparks and fuel, but what about air: are all the butterflies opening?

Peter

Link to post
Share on other sites

Mac,

What sort of manifold do you have?

If you have a 6-2-1, or rather a 6-2, with two tails all the way back, then the smoking pipe will point straight to the front or back cylinders.

That would be unusual!

 

If your manifold goes down to a single tail pipe, then splits, to two silencer boxes, then I think that the turbulence in the pipe will mix the gases too much to say that one deals with one half of then engine. So if one smokes, it must come from after the split. Do you have a new silencer, that might have paint being burnt off inside? Or is there an air leak into one side?

 

John

Link to post
Share on other sites

The spark might not be right on all cylinders. Check in the dark for stray HT. Could be disy cap arcing, or rotor arm. Are you on points? or electronic pick-up?

Link to post
Share on other sites

Hi Mac

 

Are they refurbed throttle bodies, if so they may need some time to build up a bit of carbon around the body to butterflies. Are the butterflies balanced. Might explain why the engine seems to run more smoothly as revs increase.

Link to post
Share on other sites

Mac,

What sort of manifold do you have?

If you have a 6-2-1, or rather a 6-2, with two tails all the way back, then the smoking pipe will point straight to the front or back cylinders.

That would be unusual!

 

If your manifold goes down to a single tail pipe, then splits, to two silencer boxes, then I think that the turbulence in the pipe will mix the gases too much to say that one deals with one half of then engine. So if one smokes, it must come from after the split. Do you have a new silencer, that might have paint being burnt off inside? Or is there an air leak into one side?

 

John

Thanks John, good point, I have twin exhaust (MOSS I think) all the way back to the manifold, so by the look of it the LH tail pipe serves the front 3 cylinders....

Link to post
Share on other sites

Hi Mac

 

Are they refurbed throttle bodies, if so they may need some time to build up a bit of carbon around the body to butterflies. Are the butterflies balanced. Might explain why the engine seems to run more smoothly as revs increase.

Thanks Kevo, I've not had the throttle bodies refurbed (or balanced) just cleaned up etc. I'm trying to understand why that would cause rough idle, are you saying that air might be getting into (say) cylinder 1 at idle causing uneven idle and hence this would disappear once throttle opens (as slight difference in opening unnoticeable once butterflies are open...). It is a good point but would it cause the smokey tail pipe (which btw is white) ? thanks.

Link to post
Share on other sites

Mac, White smoke, that persists longer than steam, is glycol antifreeze burning. That suggests gasket leaking. Re-torque the head bolts, you might be lucky.

If that doesnt cure the problem - and I think it probably wont - then compression test will narrow down the cylinder(s) affected. Then new gasket.

Peter

Link to post
Share on other sites

Hi Mac

If you have cleaned off the crud around the butterflies on the throttle bodies this will allow more air in around the butterflies and make it difficult to balance the butterflies and subsequently causing a lumpy tick over, crud will build up after time. Balance them and see if that makes any difference.

Before you do this I would suggest you take Peter’s advice and do a compression test, as I had similar problems (admittedly through all of the rev range) and my head gasket had gone big time.

As for the white smoke again take Peter's advice.

Link to post
Share on other sites

Hi Mac

If you have cleaned off the crud around the butterflies on the throttle bodies this will allow more air in around the butterflies and make it difficult to balance the butterflies and subsequently causing a lumpy tick over, crud will build up after time. Balance them and see if that makes any difference.

Before you do this I would suggest you take Peter’s advice and do a compression test, as I had similar problems (admittedly through all of the rev range) and my head gasket had gone big time.

As for the white smoke again take Peter's advice.

 

 

Mac, White smoke, that persists longer than steam, is glycol antifreeze burning. That suggests gasket leaking. Re-torque the head bolts, you might be lucky.

If that doesnt cure the problem - and I think it probably wont - then compression test will narrow down the cylinder(s) affected. Then new gasket.

Peter

Thanks guys, forgot to mention I did do a compression test and got 13 Bar on each cylinder (cold), which I assume is fine. I'll try tinkering with the balance on the butterflies 1,2&3. and see if that makes a difference. But it still feels down on power which leads me back to maybe only firing properly on 5. Will do a bit more research and do an update post if I'm still stuck. Thanks again. Mac.

Link to post
Share on other sites

Thanks John, good point, I have twin exhaust (MOSS I think) all the way back to the manifold, so by the look of it the LH tail pipe serves the front 3 cylinders....

I have the same twin exhaust arrangement. I had the LH pipe very hot and the RH pipe rather cold. Problem was bad adjustment of the 6 butterflies: butterflies 5 and 6 stayed still closed, when 1 to 4 were already somewhat open. As all cylinders get the same amount of petrol injected, the cylinders 5 and 6 getting not enough air, the mixture was too fat and did only occasionally explose.

I am quite sure you have the same problem.

Re-adjusting the links between the 3 blocs does help for a few days.....!

The only longterm solution seems to be mounting an auxiliary shaft for transmitting the movement individually to each bloc. See e.g. Prestige Triumph.

Link to post
Share on other sites

Why would it be a head gasket problem, the engine has just been built?

 

I think Wilfried has it spot on. Butterfly imbalance is causing the front 3 (or most of them) to run rich and rear 3 to run lean. Lean runs much hotter and will clear steam faster. Rich will run colder, steam for longer and possibly black smoke a bit too.

 

Balancing the throttle bodies and linkage should be first move IMO.

 

Nick

Link to post
Share on other sites

Why would it be a head gasket problem, the engine has just been built?

 

I think Wilfried has it spot on. Butterfly imbalance is causing the front 3 (or most of them) to run rich and rear 3 to run lean. Lean runs much hotter and will clear steam faster. Rich will run colder, steam for longer and possibly black smoke a bit too.

 

Balancing the throttle bodies and linkage should be first move IMO.

 

Nick

Nick

The post was titled: "One tailpipe smoking".

We learned later it was white smoke.

Now its ....I dunno.

Peter

Edited by Peter Cobbold
Link to post
Share on other sites

Why would it be a head gasket problem, the engine has just been built?

 

I think Wilfried has it spot on. Butterfly imbalance is causing the front 3 (or most of them) to run rich and rear 3 to run lean. Lean runs much hotter and will clear steam faster. Rich will run colder, steam for longer and possibly black smoke a bit too.

 

Balancing the throttle bodies and linkage should be first move IMO.

 

Nick

Mac,

Before touching anything else just do this:

Open the bonnet and look for the cable from the accelleration pedal to the butterfly mechanism.

Pull the cable very gently upwards and observe the movement of the three butterfly assemblies. (You cannot see the butterflies, but only the three axis on which they are mounted.)

In your case you will most probably see that the first (front) assembly and probably the second moves first when you pull the cable. The third (rear) will move a bit later, because the linkage between them is not well adjusted (and is of bad design).

 

I would be very interested to read you, once you have made this test. It just takes some minutes and you don't need to start the engine.

 

Wilfried

Link to post
Share on other sites

Mac,

Before touching anything else just do this:

Open the bonnet and look for the cable from the accelleration pedal to the butterfly mechanism.

Pull the cable very gently upwards and observe the movement of the three butterfly assemblies. (You cannot see the butterflies, but only the three axis on which they are mounted.)

In your case you will most probably see that the first (front) assembly and probably the second moves first when you pull the cable. The third (rear) will move a bit later, because the linkage between them is not well adjusted (and is of bad design).

 

I would be very interested to read you, once you have made this test. It just takes some minutes and you don't need to start the engine.

 

Wilfried

Thanks Wilfried and Nick,

I spent some time yesterday balancing the the throttle bodies and it does seem to have helped !

I just tried Wilfried's test and the mechanisms now start to move together.

Unfortunately I ran out of petrol during tests ! so will top up tomorrow and see if it runs any better.

Many thanks.

Mac.

Link to post
Share on other sites

Thanks Wilfried and Nick,

I spent some time yesterday balancing the the throttle bodies and it does seem to have helped !

I just tried Wilfried's test and the mechanisms now start to move together.

Many thanks.

Mac.

Mac,

One more caveat:

The thee throttlebodies are now well balanced. When you pull the starter knob to start the cold engine, this may ruin your good balance. The starter knob pulls 2 cables, one going to measuring device to inject more fuel, the other to the rear(!) throttle body to open a little the 6 butterflies.

This means: when you accelerate by pressing the pedal, the linkages between the throttle bodies are "stressed" from the front to the rear (because the cable from the pedal is pulling on the first body). When you pull the starter knob, the linkage is stressed from the rear to the front, i.e. it opens the rear throttles and through the linkage then the front throttles.

In my case, after a few starts with pulling the starter knob, the good adjustment became again bad, because of the poor design of the linkages.

Wilfried

Link to post
Share on other sites

The word on the forum is to disconnect the 'cold start' cable from the butterflies, so that it operates on the pdm only.

I understand that this results in more even starting and running.

 

I am planning to give it a try, but, with weather as it is around here, the car is going nowhere for a while.

I will report back as and when

 

Can anyone offer more info?

 

John

Edited by wjgco
Link to post
Share on other sites

Mac,

One more caveat:

The thee throttlebodies are now well balanced. When you pull the starter knob to start the cold engine, this may ruin your good balance. The starter knob pulls 2 cables, one going to measuring device to inject more fuel, the other to the rear(!) throttle body to open a little the 6 butterflies.

This means: when you accelerate by pressing the pedal, the linkages between the throttle bodies are "stressed" from the front to the rear (because the cable from the pedal is pulling on the first body). When you pull the starter knob, the linkage is stressed from the rear to the front, i.e. it opens the rear throttles and through the linkage then the front throttles.

In my case, after a few starts with pulling the starter knob, the good adjustment became again bad, because of the poor design of the linkages.

Wilfried

That not how I remember the cold start cable operating on my old CP car. IIRC the snail cam operated near the centre of the linkage. Memory coulld be playing tricks though. Edited by peejay4A
Link to post
Share on other sites

Only just now seen the significance of the title of this thread.

 

Teach us, O Masters of TR Zen!

If we study the sound of one hand clapping, how much more can we learn from the sight of one tailpipe smoking!

 

John (Jo-Un, Pure Cloud)

Link to post
Share on other sites

I have just checked and the cold start throttle opening cam on my CP. It operates at the front throttle body while the throttle cable acts at the middle body. My cold start is not connected to the throttle (never has been since I have had the car) just to the enrichment lever on the metering unit.

 

Tried to take a picture to sow this but is was impossible to get a decent shot.

 

Bruce

Link to post
Share on other sites

Mac,

One more caveat:

The thee throttlebodies are now well balanced. When you pull the starter knob to start the cold engine, this may ruin your good balance. The starter knob pulls 2 cables, one going to measuring device to inject more fuel, the other to the rear(!) throttle body to open a little the 6 butterflies.

This means: when you accelerate by pressing the pedal, the linkages between the throttle bodies are "stressed" from the front to the rear (because the cable from the pedal is pulling on the first body). When you pull the starter knob, the linkage is stressed from the rear to the front, i.e. it opens the rear throttles and through the linkage then the front throttles.

In my case, after a few starts with pulling the starter knob, the good adjustment became again bad, because of the poor design of the linkages.

Wilfried

Mac,

I definitively refere to CR engine! I

Wilfried

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.