Does anybody know what the correct compression figures should be for the 1.6 XU51C carb engine?
Cheers,
Derek
Compression test
Moderator: RichardW
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FrenchLeave
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We did one yesterday on an Mi16 with cat (the lower compression version)that was running badly but had been worked on in the past few months and it came out at 180 psi per cylinder.
On most passenger cars, around 160/180 is acceptable, sports cars or high compression emgines around 180/225.
I would suggest on that engine around the 150/180 would be close enough not knowing the c/r. For purposes of testing the internal condition of an engine though, the readings should preferrably be within 10% of each other (ie) Cyl #1 is 150 psi, then if cyl #2 was 180 or 115 as an example, that would indicate rings or valves worn. Whereas 150 against 160 is acceptable.
Alan S
On most passenger cars, around 160/180 is acceptable, sports cars or high compression emgines around 180/225.
I would suggest on that engine around the 150/180 would be close enough not knowing the c/r. For purposes of testing the internal condition of an engine though, the readings should preferrably be within 10% of each other (ie) Cyl #1 is 150 psi, then if cyl #2 was 180 or 115 as an example, that would indicate rings or valves worn. Whereas 150 against 160 is acceptable.
Alan S
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FrenchLeave
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Thanks Alan, mine came out between 162 and 170 psi. Putting in a teaspoon of oil increased the figures to 185.
I'm trying to find cause of a heavy whitish brown smoke discharge from the exhaust on the wife's car.
Thinking of squirting in some Holts Piston Seal but it seems like a very un engineering way of dealing with the problem.
Derek.
I'm trying to find cause of a heavy whitish brown smoke discharge from the exhaust on the wife's car.
Thinking of squirting in some Holts Piston Seal but it seems like a very un engineering way of dealing with the problem.
Derek.
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A blow from the ball on a ball peen hammer will often cure local porosity problems, I used it to cure leaks on gunmetal castings made to withstand quite high water pressures with a high percentage of success for several years, it was also a common practice to cure leaks both on cast iron and ally heads in the pump and compressor engineering workshop I worked in as a lad... Neither of those were combustion chamber issues, but I see no reason to believe it wont work in many cases where the head is slightly porous in a localised area..
Some additives do work in as much as they help shift gunge that's formed in the piston ring grooves etc and allow the rings to move again.. For what it costs its worth a try..
.
Some additives do work in as much as they help shift gunge that's formed in the piston ring grooves etc and allow the rings to move again.. For what it costs its worth a try..
.
all piston ring sealer dose is gundges up the gap between rings and piston,and stops any oil getting around rings so they burn out,any way blue smoke indicates oil being burnt,what car is it because if its not a hydraulic susp car it could be brake fluid being sucked into inlet manifold and being burnt regards malcolm
If putting oil in the cylinder increased the compo then it's your piston rings my friend. If oil has no effect then turn your attention to the head and valvetrain. Gravity will prevent the oil poured into the spark plug hole from sealing the valve stem oil seals etc and so will only help the piston rings seal better and increase the compo.
White smoke, black smoke and blue smoke I can explain, but a brownish colour is usually a sign that there's a baffle disintegrating inside a muffler or pong box and this is often the insulation burning out, turning to dust and blowing out the back taking the rusty scale from inside the exhaust system with it.
What kind of fuel are you using also?
Alan S
What kind of fuel are you using also?
Alan S
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FrenchLeave
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Be sure youre sins will find you out!
I have to admit its a Pug 309 Auto, I posted the same query on the Pug part of the forum and got zilch so I thought "Aha, I know a bunch of fellas that'll come up with some answers." So I broke the rules by posting a Pug problem on the Cit forum. It is the same type of engine as the one I had in my old BX 16TRS - except that its got a godawful Solex carb instead of the Weber.
This car failed its MOT a couple of years ago and I bought Mrs W a ZX 1.9D to replace it. She offered it to no 3 son who still lives at home but two years later he's done nothing (to the car or anything else). It's only done 76,000 miles and is virtually unmarked. I think it's too good to scrap so I thought I'd have a look myself.
Thank you all for taking the time and trouble to answer, I've followed up some of your leads with the following results:
MOT failure gives no figures, just says "CO excessively high, excessive smoke".
There is a separate coolant header tank, the level doesn't seem to have dropped and there is no contamination. Removing the cap with the engine running doesn't show any activity - not sure what I expected to see.
Removed the engine breather hose from the carb intake with the engine running, no smoke, no excessive blowby. Does this suggest that the rings are OK?.
When the engine is first started there is no smoke. As it warms up so the smoke increases and when at operating temp its like a smoke generator. It's there at idling, it's there under power. Looking closely at it through the fug that surrounds the car, there is a definite blue tinge. This seems to have changed since I last ran it.
Oil level has not dropped in the last 200 miles.
Brake fluid level is still at the full level.
The engine has always been a pig to start from cold, the float chamber seemed to empty itself overnight. I disconnected the automatic choke and fitted a manual one because the auto one was reluctant to return to normal mixture. Fuel consumption has been pretty awful - never better than 26 mpg, nevertheless, once running the engine is smooth and quiet with a nice even tickover and no signs of rich hunting. Plugs did look black when I did the compression test.
I'm wondering if its worth while fitting new jets, although I don't think it's possible for the engine to have been running rich enough to produce that amount of smoke.
The other possibility is your suggestion of valve seals, Kowalski. I've had a quick look in Haynes and it looks pretty horrid!
Tongue in cheek, what are the chances of sliding a 1.9D in there?
What do you all think?
Derek.
I have to admit its a Pug 309 Auto, I posted the same query on the Pug part of the forum and got zilch so I thought "Aha, I know a bunch of fellas that'll come up with some answers." So I broke the rules by posting a Pug problem on the Cit forum. It is the same type of engine as the one I had in my old BX 16TRS - except that its got a godawful Solex carb instead of the Weber.
This car failed its MOT a couple of years ago and I bought Mrs W a ZX 1.9D to replace it. She offered it to no 3 son who still lives at home but two years later he's done nothing (to the car or anything else). It's only done 76,000 miles and is virtually unmarked. I think it's too good to scrap so I thought I'd have a look myself.
Thank you all for taking the time and trouble to answer, I've followed up some of your leads with the following results:
MOT failure gives no figures, just says "CO excessively high, excessive smoke".
There is a separate coolant header tank, the level doesn't seem to have dropped and there is no contamination. Removing the cap with the engine running doesn't show any activity - not sure what I expected to see.
Removed the engine breather hose from the carb intake with the engine running, no smoke, no excessive blowby. Does this suggest that the rings are OK?.
When the engine is first started there is no smoke. As it warms up so the smoke increases and when at operating temp its like a smoke generator. It's there at idling, it's there under power. Looking closely at it through the fug that surrounds the car, there is a definite blue tinge. This seems to have changed since I last ran it.
Oil level has not dropped in the last 200 miles.
Brake fluid level is still at the full level.
The engine has always been a pig to start from cold, the float chamber seemed to empty itself overnight. I disconnected the automatic choke and fitted a manual one because the auto one was reluctant to return to normal mixture. Fuel consumption has been pretty awful - never better than 26 mpg, nevertheless, once running the engine is smooth and quiet with a nice even tickover and no signs of rich hunting. Plugs did look black when I did the compression test.
I'm wondering if its worth while fitting new jets, although I don't think it's possible for the engine to have been running rich enough to produce that amount of smoke.
The other possibility is your suggestion of valve seals, Kowalski. I've had a quick look in Haynes and it looks pretty horrid!
Tongue in cheek, what are the chances of sliding a 1.9D in there?
What do you all think?
Derek.
The last info I think we need is what kind of oil you have got in that engine.
I tried a "good oil" in my running '89 BX16 (type XU5) engine - that is a modern synt 5w-40. It burned out the exhaust in a week with a constant blue smoke [:(]
I take it this engine has been given a fair chance with fresh engine oil ?
If the exhaust smoke has a blue tinge it's definately some engine oil being burnt in the combustion.
The massive white smoke is either coolant or oil getting directly into the exhaust - then evapourated but not burnt.
Any blowby would cause a pressurised breather system.
Now - if the HG had failed in a waterway to a cylinder - you would definately get an insane pressure in the cooling system. Severity from this is seen as the intensity of bubbles from the capless headertank.
There are a few other things that can make an otherwise good, well serviced and healthy carb engine go nuts on CO-level :
1) Wrong working temperature from a defective cooling thermostat. Common problem is the thermostat stuck open which gives warm up times in the hours range. This often leads to wrongly adjusted carbs to at least give the engine a steady idle.
2) Carburettor jets swapped. I.e. main jet and aux jet swapped around during any overhaul. A common DIY problem [:)]
Note that if the car has stand still for many months - it may smoke for hours before the exhaust has been cleaned out for any seeped out oil - and lot's of condensed water. Only cure is to drive the engine for hours with patience. Knowing of course there are no other severe problems.
I tried a "good oil" in my running '89 BX16 (type XU5) engine - that is a modern synt 5w-40. It burned out the exhaust in a week with a constant blue smoke [:(]
I take it this engine has been given a fair chance with fresh engine oil ?
If the exhaust smoke has a blue tinge it's definately some engine oil being burnt in the combustion.
The massive white smoke is either coolant or oil getting directly into the exhaust - then evapourated but not burnt.
Any blowby would cause a pressurised breather system.
Now - if the HG had failed in a waterway to a cylinder - you would definately get an insane pressure in the cooling system. Severity from this is seen as the intensity of bubbles from the capless headertank.
There are a few other things that can make an otherwise good, well serviced and healthy carb engine go nuts on CO-level :
1) Wrong working temperature from a defective cooling thermostat. Common problem is the thermostat stuck open which gives warm up times in the hours range. This often leads to wrongly adjusted carbs to at least give the engine a steady idle.
2) Carburettor jets swapped. I.e. main jet and aux jet swapped around during any overhaul. A common DIY problem [:)]
Note that if the car has stand still for many months - it may smoke for hours before the exhaust has been cleaned out for any seeped out oil - and lot's of condensed water. Only cure is to drive the engine for hours with patience. Knowing of course there are no other severe problems.
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Kowalski
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You can get blue smoke from a car by running it rich but it has to be very rich, i.e. severe problems with the carb or the injection system. 26mpg could indicate that its running horribly rich or it could just be town driving having that effect. Have you tried the standard Italian tune up?
If all is well with the fuel system and its just burning oil, as Anders says old engines don't like new oils, stick some 20-50 in. If it still burns the thick oil, stick one of those additives in that stops the engine burning oil, I wouldn't recommend this permanantly (or at all really) but it might have enough of an effect to get you through the MOT.
If all is well with the fuel system and its just burning oil, as Anders says old engines don't like new oils, stick some 20-50 in. If it still burns the thick oil, stick one of those additives in that stops the engine burning oil, I wouldn't recommend this permanantly (or at all really) but it might have enough of an effect to get you through the MOT.
Now we're getting somewhere possibly. Let's forget about trying to define the smoke.
My first BX was a 16Trs. Not only that, it was also an Auto that had been reborn as a manual. The previous owner was a Citroen specialist and renown stuff arounder who can talk a bill up even if the original job was only testing air pressure in the tyres, so I expected strange dramas; I was not disappointed.
Fuel consumption around town at best was 20mpg (13.75L/100klms)and on a trip around 23.
I started at the carby and found the idle jet (Weber carb but was the same on a Solex I understand) was a 70. Book says 45 so I changed it to that. Checked the rest, cleaned out and refitted. I'll get a bit ahead of myself now for clarity as this is still carby related and this carby work should probably be best done as the last part of all this work.
Set the float level to the lowest it will comfortably run on. I based this on many years of tuning CXs; a float set too high will guzzle fuel of that there's no doubt. The setting from memory is 7mm + or - 2mm. This can be very time consuming and not something a garage could even think of doing this way because of that. I started around 10mm, reassembled and tested; it was too low. To test, take the car to a quiet stretch of straight road and simply "flatten it" in the first 2 or 3 gears. If it revs right out, you've got it. If it's too low it will stutter as the revs get higher. Adjust up about 1mm and try again. Keep doing this until the engine sounds like it would just about destroy itself if you left the foot on the floor. Hard to describe, but you'll know when you get it right as they sound "crisp."
Having got all that right, then look to the air supply set up. They should have an air intake hose, flexible about 75mm diameter, leading from under the front guard to a box with a thermostatically controlled flap on it and leading to the carb and the hot box on the exhaust manifold. This helps keep the ambiaent temp to the carby fairly constant. Out here we have this fallacy that they are not needed so they throw them away. When the initial throtttle settings are made, they are done based on ambient temp as Anders referred to and set accordingly. In the carb there is a 'fuel enrichment device' (don't ask me to give any better description as even Haynes has problems with it) which until the optimum operating temp is reached, will 'enrichen' the mix of fuel to air ratio to compensate for the cooler weather.
As Anders points out, there's every chance the thermostat is on the way out as they have a short life expectancy so again, temperature is playing a vital role.
Having sorted all that, I then went looking carefully at the breather system and again, got some surprises. Amongst the myriad of pipes and hoses, you'll find a couple of things that resemble green or yellowy coloured golf balls with breather hoses leading to & from them. These can be pulled apart and inside they reveal a series of discs that are honeycombed with holes and are corrugated. Seperate the discs and soak in either kero or a heavy duty degreaser. If you can get Phenyle, that's as good a degreaser you'll get for this type of thing. Mostly they are welded together with solid crap. Nothing could get through it and it will take at least a couple of days before the muck softens.
When I had done all this, I found I got 28/30 mpg around town and 40mpg highway cycle. (38 with the air/con on)
When I sold the car, I explained all this to the new owner who a couple of months later took it to another "specialist" who was as bad as the one I bought it off and one I warned her to stay away from. He told her I didn't have a clue what I was talking about and set about removing the air hose to the hotbox, resetting the float level and "going over" the car and in the process handing her a monster bill.
She rang fairly abusive that there was so much wrong with the car whilst admitting she only took it to him for an oil change and general service service as it was running fine, (the term 'getting screwed' comes to mind) and now she was only getting about 20mpg so I had obviously bodged the engine to sell it to her ( the term 'getting conned by the specialist' comes to mind.) She eventually had her father look at it and reset everything back to where it was when she bought it and last I heard had done 60,000 trouble free klms in it.
So FWIW, I'd suggest follow what I did and I think you may be getting a bit close to solving the problems.
Alan S
My first BX was a 16Trs. Not only that, it was also an Auto that had been reborn as a manual. The previous owner was a Citroen specialist and renown stuff arounder who can talk a bill up even if the original job was only testing air pressure in the tyres, so I expected strange dramas; I was not disappointed.
Fuel consumption around town at best was 20mpg (13.75L/100klms)and on a trip around 23.
I started at the carby and found the idle jet (Weber carb but was the same on a Solex I understand) was a 70. Book says 45 so I changed it to that. Checked the rest, cleaned out and refitted. I'll get a bit ahead of myself now for clarity as this is still carby related and this carby work should probably be best done as the last part of all this work.
Set the float level to the lowest it will comfortably run on. I based this on many years of tuning CXs; a float set too high will guzzle fuel of that there's no doubt. The setting from memory is 7mm + or - 2mm. This can be very time consuming and not something a garage could even think of doing this way because of that. I started around 10mm, reassembled and tested; it was too low. To test, take the car to a quiet stretch of straight road and simply "flatten it" in the first 2 or 3 gears. If it revs right out, you've got it. If it's too low it will stutter as the revs get higher. Adjust up about 1mm and try again. Keep doing this until the engine sounds like it would just about destroy itself if you left the foot on the floor. Hard to describe, but you'll know when you get it right as they sound "crisp."
Having got all that right, then look to the air supply set up. They should have an air intake hose, flexible about 75mm diameter, leading from under the front guard to a box with a thermostatically controlled flap on it and leading to the carb and the hot box on the exhaust manifold. This helps keep the ambiaent temp to the carby fairly constant. Out here we have this fallacy that they are not needed so they throw them away. When the initial throtttle settings are made, they are done based on ambient temp as Anders referred to and set accordingly. In the carb there is a 'fuel enrichment device' (don't ask me to give any better description as even Haynes has problems with it) which until the optimum operating temp is reached, will 'enrichen' the mix of fuel to air ratio to compensate for the cooler weather.
As Anders points out, there's every chance the thermostat is on the way out as they have a short life expectancy so again, temperature is playing a vital role.
Having sorted all that, I then went looking carefully at the breather system and again, got some surprises. Amongst the myriad of pipes and hoses, you'll find a couple of things that resemble green or yellowy coloured golf balls with breather hoses leading to & from them. These can be pulled apart and inside they reveal a series of discs that are honeycombed with holes and are corrugated. Seperate the discs and soak in either kero or a heavy duty degreaser. If you can get Phenyle, that's as good a degreaser you'll get for this type of thing. Mostly they are welded together with solid crap. Nothing could get through it and it will take at least a couple of days before the muck softens.
When I had done all this, I found I got 28/30 mpg around town and 40mpg highway cycle. (38 with the air/con on)
When I sold the car, I explained all this to the new owner who a couple of months later took it to another "specialist" who was as bad as the one I bought it off and one I warned her to stay away from. He told her I didn't have a clue what I was talking about and set about removing the air hose to the hotbox, resetting the float level and "going over" the car and in the process handing her a monster bill.
She rang fairly abusive that there was so much wrong with the car whilst admitting she only took it to him for an oil change and general service service as it was running fine, (the term 'getting screwed' comes to mind) and now she was only getting about 20mpg so I had obviously bodged the engine to sell it to her ( the term 'getting conned by the specialist' comes to mind.) She eventually had her father look at it and reset everything back to where it was when she bought it and last I heard had done 60,000 trouble free klms in it.
So FWIW, I'd suggest follow what I did and I think you may be getting a bit close to solving the problems.
Alan S
<center>Footnote to the above posting:</center>
The air filter element is a foam type which can block and/or disintegrate fairly easily and should be regularly changed. Some make their own but use too dense a foam which can also cause fuel consumption problems.
It is also interesting to note that when set as described above, it will be necessary to run with the choke out for the first mile or two but my (proven) theory on this is that this is a minor inconvenience and as engines by nature "richen up" as they get warmer, once warmed even slightly will run faultlessly for the rest of the day.
Timing hould be set at 10 BTDC and fuel used needs to be Premium unleaded as they will not run properly on LRP or standard low grade unleaded petrol.
Alan S
The air filter element is a foam type which can block and/or disintegrate fairly easily and should be regularly changed. Some make their own but use too dense a foam which can also cause fuel consumption problems.
It is also interesting to note that when set as described above, it will be necessary to run with the choke out for the first mile or two but my (proven) theory on this is that this is a minor inconvenience and as engines by nature "richen up" as they get warmer, once warmed even slightly will run faultlessly for the rest of the day.
Timing hould be set at 10 BTDC and fuel used needs to be Premium unleaded as they will not run properly on LRP or standard low grade unleaded petrol.
Alan S