HELP! My DS is driving me mad.

T

tresbon

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Fellow Frogger
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Hobart
Ever since I got my 1970 DS21BVH I have had difficulty in tuning it so that it runs as they should.

I have been following the factory workshop manual and/or the Brooklands one. I have used the car very little since buying it over a year ago, partly because it is a pain in traffic. It stalls every time one brakes to a stop, when the idling speed drops away (below what the manual requires) I have been using a basic tacho/dwell angle/points meter, which reads much lower than the dash tacho - eg over 1000rpm vs 800 on the external unit.
Using the accelerated idle adjuster screw the highest rpm I can achieve is around 800rpm whereas the book says around 900. At idle the rpm varies by50-100rpm and no choke is required even from cold.

I have replaced most of the ignition system and that seems to be in order.
I am left wondering if there is something wrong in the hydraulic unit which operates the accelerated idle system. I can't find any details of this unit in the manuals.

Any ideas will be gratefully received.
PS - one the local DS experts had a go at this problem without success.
Don
 
I had a similar prob with my D years ago while on a long trip. Turns out a brass screw had dropped out of the bottom or lower side of the carby near the rocker cover (I think). I had to use the choke in traffic to keep it running. Replaced the screw and the engine would then maintain idle. But this could be completely unrelated to your problem as mine, of course, is not BVH.
 
skp from this forum has spent many hours getting my bvh to function properly over the past two years, like yours it was horrible to start with, it was leaping away, stalling, jerky and no fun at all...the issues stemmed from years of well meaning mechanics slowly making it worse, some of them claiming to be citroen specialists. I can now report that it is an absolute joy to drive, but it took a carby overhaul and then some serious faffing, multiple tunes, rebuild of clutch re-engagment control and more fiddling with idle. The idle is still slightly higher than it should be and there may be a bit more on the carby tuning to get to perfection.
In short, although I did none of the work other than pay the bills on this, I saw enough to know that it requires a very deep understanding of the different factors at play as with a bvh everything seems to be connected to eveything else and it is possible to be on completely the wrong track without realising it. There are experts on this forum who can explain the basics in far more detail than I, but in short I suggest you PM skp or other experts from this forum and track down someone who really knows their way around the bvh in Adelaide as it is well worth it. I do have a pretty rough hard-copy of Rod Dellinger's paper on setting up the bvh and another by Charles Vyse 2003. But you may be able to find these in the Citroen references on-line, otherwise I could scan them for you.

Cheers

Mark
 
Yes, why not? If I can't fix it myself. It's the challenge you know!

Actually I have now realised that the accelerated idle control is obviously working and I am guessing that it is just an on/off switch, operated by the lefthand front brake, which is why the bleed screw for that brake is mounted on the control unit. The screw presumably controls the amount of extra mixture when the brake is not on.
So I am now thinking that I need to get the normal idle speed up. Strangely, no matter how far I screw in the the secondary butterfly stop screw it makes little difference.
 
cactus61 said:
skp from this forum has spent many hours getting my bvh to function properly over the past two years, like yours it was horrible to start with, it was leaping away, stalling, jerky and no fun at all...the issues stemmed from years of well meaning mechanics slowly making it worse, some of them claiming to be citroen specialists. I can now report that it is an absolute joy to drive, but it took a carby overhaul and then some serious faffing, multiple tunes, rebuild of clutch re-engagment control and more fiddling with idle. The idle is still slightly higher than it should be and there may be a bit more on the carby tuning to get to perfection.
In short, although I did none of the work other than pay the bills on this, I saw enough to know that it requires a very deep understanding of the different factors at play as with a bvh everything seems to be connected to eveything else and it is possible to be on completely the wrong track without realising it. There are experts on this forum who can explain the basics in far more detail than I, but in short I suggest you PM skp or other experts from this forum and track down someone who really knows their way around the bvh in Adelaide as it is well worth it. I do have a pretty rough hard-copy of Rod Dellinger's paper on setting up the bvh and another by Charles Vyse 2003. But you may be able to find these in the Citroen references on-line, otherwise I could scan them for you.

Cheers

Mark
Click to expand...

Thanks Mark. You just reminded me that I have a detailed article on BVH tuning, probably one of those you quoted. As I recall I used it previously to the letter but without success. Will check it again.

Don
 
cactus61 said:
skp from this forum has spent many hours getting my bvh to function properly over the past two years, like yours it was horrible to start with, it was leaping away, stalling, jerky and no fun at all...the issues stemmed from years of well meaning mechanics slowly making it worse, some of them claiming to be citroen specialists. I can now report that it is an absolute joy to drive, but it took a carby overhaul and then some serious faffing, multiple tunes, rebuild of clutch re-engagment control and more fiddling with idle. The idle is still slightly higher than it should be and there may be a bit more on the carby tuning to get to perfection.
In short, although I did none of the work other than pay the bills on this, I saw enough to know that it requires a very deep understanding of the different factors at play as with a bvh everything seems to be connected to eveything else and it is possible to be on completely the wrong track without realising it. There are experts on this forum who can explain the basics in far more detail than I, but in short I suggest you PM skp or other experts from this forum and track down someone who really knows their way around the bvh in Adelaide as it is well worth it. I do have a pretty rough hard-copy of Rod Dellinger's paper on setting up the bvh and another by Charles Vyse 2003. But you may be able to find these in the Citroen references on-line, otherwise I could scan them for you.

Cheers

Mark
Click to expand...

Yes, praise for skp is apt. And I can verify that cactus61's car is a joy to drive. I'm still smiling 6 months later....

My Kent Town Autotune comment is very much to do with carbie/tuning matters not BVH by the way. I imagine that if there is a basic carbie/tuning problem as well as BVH matters, it might be a tad challenging to separate the issues.
 
I'd expect completely resetting the carby and then following the BVH adjustment procedure in the manual step by step, in order would be the best way to proceed. Cleaning, rekitting and correctly setting up the linkages etc. on a D Special carby transformed that particular car, so it may also be worthwhile here. From memory, setting the slip of the clutch requires the starting handle to get right and Russek's little handbook has concise instructions - if you can find a copy.
 
tresbon2 said:
Yes, why not? If I can't fix it myself. It's the challenge you know!

Actually I have now realised that the accelerated idle control is obviously working and I am guessing that it is just an on/off switch, operated by the lefthand front brake, which is why the bleed screw for that brake is mounted on the control unit. The screw presumably controls the amount of extra mixture when the brake is not on.
So I am now thinking that I need to get the normal idle speed up. Strangely, no matter how far I screw in the the secondary butterfly stop screw it makes little difference.
Click to expand...

Things to keep in mind and look for:

1) Base of carb is flat - not warped

2) Primary throttle shaft in carb body is tight and cannot be wiggled up/down or side to side at all

3) That the primary throttle stop has not been 'adjusted'. The factory clearance for the primary throttle plate is 0.003" clearance to the venturi. Or another way of looking at it is that the edge of the throttle plate just completely covers the first progression hole drilled in the primary venturi. Once set the adjusting screw should be locked in place and not touched.

4) On a 70 21 engine the secondary jets should be 0.50 and 0.70mm. It is the secondary throttle that contains the idle circuit.

5) Check the idle mixture screw - its tapered end should be smooth and without any noticeable wear

The accelerated idle device is nothing more than a spring loaded shut off valve. When the front brakes are 'on' it closes off the aux. air passage in the carb body. Brakes 'off' and the amount of air allowed to flow into the base of the secondary venturi is adjusted by the aux air mixture screw (the big brass one). That you have a 'hunting' idle is a good indication that the carb base is warped, the primary throttle shaft hole in the carb body is no longer round or both. Either condition allows excess (and non metered air) into the intake manifold.

Keep firmly in mind that all idle adjustments to the two barrel Weber carbs as fitted to the 5 main D's is done with the secondary throttle - only.

The BVH controls while affecting gear shifting and clutch action have no affect on the carb. Carb set up, OTOH, has a noticeable affect on BVH performance :).

Steve
 
Citroenfan said:
Things to keep in mind and look for:

1) Base of carb is flat - not warped

2) Primary throttle shaft in carb body is tight and cannot be wiggled up/down or side to side at all

3) That the primary throttle stop has not been 'adjusted'. The factory clearance for the primary throttle plate is 0.003" clearance to the venturi. Or another way of looking at it is that the edge of the throttle plate just completely covers the first progression hole drilled in the primary venturi. Once set the adjusting screw should be locked in place and not touched.

4) On a 70 21 engine the secondary jets should be 0.50 and 0.70mm. It is the secondary throttle that contains the idle circuit.

5) Check the idle mixture screw - its tapered end should be smooth and without any noticeable wear

The accelerated idle device is nothing more than a spring loaded shut off valve. When the front brakes are 'on' it closes off the aux. air passage in the carb body. Brakes 'off' and the amount of air allowed to flow into the base of the secondary venturi is adjusted by the aux air mixture screw (the big brass one). That you have a 'hunting' idle is a good indication that the carb base is warped, the primary throttle shaft hole in the carb body is no longer round or both. Either condition allows excess (and non metered air) into the intake manifold.

Keep firmly in mind that all idle adjustments to the two barrel Weber carbs as fitted to the 5 main D's is done with the secondary throttle - only.

The BVH controls while affecting gear shifting and clutch action have no affect on the carb. Carb set up, OTOH, has a noticeable affect on BVH performance :).

Steve
Click to expand...

Thanks for that Steve. To answer your 5 points -
1) Carb base could be warped; I will check, when i get time.
2) the shaft is very tight.
3) Oh dear, The primary throttle stop HAS been adjusted - not by me but by the 'expert'. What can I do now?
4) I checked the jets last year and they were to specn.
5) Good idea. I will check the screw. If it is worn I guess that I need a new/good one.

I am surprised that both the secondary stop screw and the accelerated idle screw have little or no affect, even the mixture screw also, unlike any other carby I have ever adjusted. Methinks I must check that carb base!

I have no real issue with the BVH system, which seems to work OK. My problem is with the stalling when braking. Which would indicate that the normal idle speed is not high enough perhaps. (I don't have a lot of faith in my old basic tacho, or the dash one)
 
tresbon2 said:
Thanks for that Steve. To answer your 5 points -
1) Carb base could be warped; I will check, when i get time.
2) the shaft is very tight.
3) Oh dear, The primary throttle stop HAS been adjusted - not by me but by the 'expert'. What can I do now?
4) I checked the jets last year and they were to specn.
5) Good idea. I will check the screw. If it is worn I guess that I need a new/good one.

I am surprised that both the secondary stop screw and the accelerated idle screw have little or no affect, even the mixture screw also, unlike any other carby I have ever adjusted. Methinks I must check that carb base!

I have no real issue with the BVH system, which seems to work OK. My problem is with the stalling when braking. Which would indicate that the normal idle speed is not high enough perhaps. (I don't have a lot of faith in my old basic tacho, or the dash one)
Click to expand...

Easy way to check for base warp is to direct a thin spray of carb or brake cleaner around the base of the carb with the engine running. If you get a noticeable increase in speed - the base is not air tight.

To set the primary throttle plate. Remove the carb. Turn upside down - using a magnifying glass or glasses carefully adjust the primary throttle plate so that its edge just covers the first of the tiny progression holes in the venturi wall. That setting is correct when the smallest movement of the primary shaft causes the primary throttle plate to just start to uncover that first progression hole. Those little progression holes are supplied with fuel via the secondary or 'low speed' jet. The main jet only starts to become affective when engine speed is above 1700 to 2000 rpm or so.

Make sure the actual idle circuit in the carb is clear - blow compressed air through the body of the carb via the so called 'idle jet' opening that scews into the secondary venturi side of the carb body. Make sure it is clean also.

Remove the top cover. Closely examine the secondary circuit air correction jets. These will be small, calibrated, holes drilled into the top plate of the carb body. Ensure that they are not clogged. Check for tightness of the main circuit(s) air correction jets and emulsion tubes.

Remove the accelerated idle device and ensure that the spring return for the plunger is in place. Ensure that the little piston moves freely. When removing the unit from the carb, be careful, as the brass air stop/ spring can be easily lost.

If the base in not warped, you get the position of the primary throttle set correctly and the idle mixture screw is not damaged - you should be able to get the idle set properly and not have the engine die on braking.

I must stress - once the primary throttle plate is set - lock the adjustment screw with its supplied lock nut. And then shoot anyone who tries to mess with it :). Adjust the low idle speed with the secondary throttle plate and the mixture screw. Adjust the accelerated idle speed with the aux air bleed. Once you think you have it right - apply the front brakes firmly and ensure that the low idle drops to your predetermined point. Drive the car until it is completely warmed upped - apply the front brakes firmly. If the engine speed drops to low, enrich the idle mixture by 1/4 to 1/3 turn of the mixture screw.

Steve

Steve
 
Citroenfan said:
Easy way to check for base warp is to direct a thin spray of carb or brake cleaner around the base of the carb with the engine running. If you get a noticeable increase in speed - the base is not air tight.

To set the primary throttle plate. Remove the carb. Turn upside down - using a magnifying glass or glasses carefully adjust the primary throttle plate so that its edge just covers the first of the tiny progression holes in the venturi wall. That setting is correct when the smallest movement of the primary shaft causes the primary throttle plate to just start to uncover that first progression hole. Those little progression holes are supplied with fuel via the secondary or 'low speed' jet. The main jet only starts to become affective when engine speed is above 1700 to 2000 rpm or so.

Make sure the actual idle circuit in the carb is clear - blow compressed air through the body of the carb via the so called 'idle jet' opening that scews into the secondary venturi side of the carb body. Make sure it is clean also.

Remove the top cover. Closely examine the secondary circuit air correction jets. These will be small, calibrated, holes drilled into the top plate of the carb body. Ensure that they are not clogged. Check for tightness of the main circuit(s) air correction jets and emulsion tubes.

Remove the accelerated idle device and ensure that the spring return for the plunger is in place. Ensure that the little piston moves freely. When removing the unit from the carb, be careful, as the brass air stop/ spring can be easily lost.

If the base in not warped, you get the position of the primary throttle set correctly and the idle mixture screw is not damaged - you should be able to get the idle set properly and not have the engine die on braking.

I must stress - once the primary throttle plate is set - lock the adjustment screw with its supplied lock nut. And then shoot anyone who tries to mess with it :). Adjust the low idle speed with the secondary throttle plate and the mixture screw. Adjust the accelerated idle speed with the aux air bleed. Once you think you have it right - apply the front brakes firmly and ensure that the low idle drops to your predetermined point. Drive the car until it is completely warmed upped - apply the front brakes firmly. If the engine speed drops to low, enrich the idle mixture by 1/4 to 1/3 turn of the mixture screw.

Steve

Steve
Click to expand...

Thanks again Steve - fantastic info.

The idle screw seems to be undamaged. Now to remove the carb;something I have been resisting, and follow your detailed instructions.

Don
 
Yes, float level was checked earlier this year, but I will be checking it again now that I have the carby off.
Don
 
tresbon2 said:
Yes, float level was checked earlier this year, but I will be checking it again now that I have the carby off.
Don
Click to expand...

Don,

Float level has little affect on the idle circuit in the 28/36 Webers as used on the 5 main D's. This is not say float level is not important for overall running. Based on what you have mentioned the problem is most likely being caused by the primary throttle plate having been 'adjusted'. What has happened is that your idle speed is being determined by the primary throttle. This has rendered the actual idle circuit in the carb useless. The idle mixture screw as well as the aux. air bleed circuit all feed into the intake manifold via the secondary venturi of the carb. Their feed drilling are located below the secondary throttle plate.

The only other thing you should check is the metered air nozzle that is screwed into the carb mounting base in the intake manifold. This little nozzle meters air from the crank case into the intake manifold below the carb. If it is crudded up with carbon/dirt/oil it will affect your idle speed adjustment. Typically one can clean the orifice by just soaking the nozzle in a bit of mineral spirits and blowing out with compressed air.

Steve
 
Folks, forget downloading Tony's manuals (if you can at the moment but that's another story). Just maintain a hotline to Steve. The little tidbits of information in this thread alone have been sensational! Thanks Steve.

Roger
 
Roger Wilkinson said:
Folks, forget downloading Tony's manuals (if you can at the moment but that's another story). Just maintain a hotline to Steve. The little tidbits of information in this thread alone have been sensational! Thanks Steve.

Roger
Click to expand...

I second that!

Steve - I have just removed the air nozzle from the inlet manifold and, surprise, it is totally blocked. So that could have been one source of the problem. The carb base is certainly not flat, so another source (I did not get around to checking with the fluid whilst running - had to take the carb off anyway)

Thanks again for your invaluable advice, Don
 
tresbon2 said:
I second that!

Steve - I have just removed the air nozzle from the inlet manifold and, surprise, it is totally blocked. So that could have been one source of the problem. The carb base is certainly not flat, so another source (I did not get around to checking with the fluid whilst running - had to take the carb off anyway)

Thanks again for your invaluable advice, Don
Click to expand...

Hi Don,

The carb base not being flat will cause a 'hunting' idle problem - and under some conditions cause problems related to what you are experiencing. Were you able to actually measure the 'warp' using a metal straight edge and feeler gauges. Small amounts of warp can be negated by making a paper gasket out of a gas resistant gasket material that is around 1mm thick. Then apply a non-hardening sealant to both sides and snug the carb up.

The plugged air inlet at the base will not cause a problem like you are having. It, does, however enrich the idle slightly that cannot be corrected with changes in mixture strength. The typical problem it causes is making the car fail its MOT if C02 % is measured.

If the carb is in overall decent shape, I feel fairly confident that when the primary throttle stop is set correctly you will be on your way to solving the problem.

While you have the unit in your hands, look carefully at the brass throttle plate in the primary barrel as well as the secondary. What you are looking for is that the edges of the plate are sharp, not rounded, and that you can see an '85' stamped in the brass. The '85' signifies the angle at which the edge as been milled. That angle + the condition of the edge can have a real affect on the operation of the carb as you come off idle.

Steve
 
Citroenfan said:
Hi Don,

The carb base not being flat will cause a 'hunting' idle problem - and under some conditions cause problems related to what you are experiencing. Were you able to actually measure the 'warp' using a metal straight edge and feeler gauges. Small amounts of warp can be negated by making a paper gasket out of a gas resistant gasket material that is around 1mm thick. Then apply a non-hardening sealant to both sides and snug the carb up.

The plugged air inlet at the base will not cause a problem like you are having. It, does, however enrich the idle slightly that cannot be corrected with changes in mixture strength. The typical problem it causes is making the car fail its MOT if C02 % is measured.

If the carb is in overall decent shape, I feel fairly confident that when the primary throttle stop is set correctly you will be on your way to solving the problem.

While you have the unit in your hands, look carefully at the brass throttle plate in the primary barrel as well as the secondary. What you are looking for is that the edges of the plate are sharp, not rounded, and that you can see an '85' stamped in the brass. The '85' signifies the angle at which the edge as been milled. That angle + the condition of the edge can have a real affect on the operation of the carb as you come off idle.

Steve
Click to expand...

Thanks once again Steve. now that the carb is off I find that the throttle spindles ARE somewhat worn (I've seen worse) I'm hoping that I can leave that as is for the moment as I don't think I have time to sort that before Sunday (French Car Day here in Adelaide)
I am having trouble getting the air inlet open but will persevere.

Don
 
tresbon2 said:
Thanks once again Steve. now that the carb is off I find that the throttle spindles ARE somewhat worn (I've seen worse) I'm hoping that I can leave that as is for the moment as I don't think I have time to sort that before Sunday (French Car Day here in Adelaide)
I am having trouble getting the air inlet open but will persevere.

Don
Click to expand...

You can use a short length of stiff wire to clean the carbon out. That orifice is 1.60mm in diameter.

Steve
 
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