Worklog of my car

[roy4matra]

But back to the engine problem...
What would cause the backfires up the carburator?

As a general rule, backfires in the intake are caused by weak mixtures and backfires in the exhaust are caused by rich mixtures, providing everything else is correct.

Roy

[roy4matra]

Hej,

The green thing is an oil separator. (Maybe there is a better word for it in English, someone can correct it.)

There are a lot of perforated discs inside to get oil from the air/fumes above the valves. The air goes into the air duct and the separated oil goes downstream the carb.

Okay, if it's just a separator it looks to be as it should. Just seemed to remember somewhere that someone said it was a oneway-valve also. But won't this draw a lot of false air to the bottom of the inlet manifold, since this is also connected to the plastic neck above the carburator?

** This is an important point you are discussing here so can I please explain for all owners not just you. **

Any engine produces a small amount of crankcase compression owing the pistons going down just the same as they produce compression in the cylinder head going up, but since the volume below is much larger, it is not a lot, but it is still there.  Now in older engines, say back in the sixties, this compression was simply vented to atmosphere but since it contains an oil mist, they often had a wire mesh that the air/oil mist had to pass through to try to retain the oil part.  However, you got a lot of oil on the roads over the years from all the engines pushing out these fumes.

Now steps were taken to stop this pollution and so more modern engines are no longer allowed to vent the crankcase to atmosphere.  You cannot simply close off any vents though without doing something about the crankcase compression.  So they decided to 'vent' it back into the engine intake and let the engine consume it.  You need to try to stop the oil passing into the carb. too, so you have an air/oil separator.  On the Murena this is the green plastic item connected to the intake below the carburettor, to the air intake elbow above the carburettor and the cam cover.

It works like this: The vacuum in the intake manifold is used to draw the air/oil out from the crankcase via the connection to the cam cover and create a slight vacuum in the crankcase.  THIS IS IMPORTANT and if it is not there you will get more oil leaks from the engine as the slight pressure tries to find a way out.  As the air/oil is drawn into the green separator the perforated discs separate the oil from the air and the tiny bit of oil is drawn into the inlet manifold below the carb. and gets consumed by the engine.  The majority of the crankcase air is drawn into the intake elbow above the carburettor and passes through it in the normal way.

Since the connection air hole into the inlet manifold below the carb. is very small and hot oil is passing through it, it can carbon up and get blocked, and the system then fails to work properly and the carburettor will probably get very oily.  So you must make sure the air hole is kept clear.  This is why one of the service items is to check this crankcase breather system periodically (every major service), checking the air hole is clear and if necessary replacing the green oil separator if it gets too clogged.  You can sometimes open it up and clean the discs and re-assemble it, but it was originally glued together so you will need to re-glue it back afterwards.

Now I know, since I have seen them, many people who modify their engines with twin side-draught carbs. or change the air intake filter system, often leave off this PCV (Positive Crankcase Ventilation) system and often just vent the cam cover to atmosphere.  This should never be done, partly as you breaking regulations, partly as you will be causing more road and air pollution, but also you are creating the right conditions for minor oil leaks from the engine crankcase.  I once saw a Murena 2.2 that continually pushed the dipstick up and unseated the rubber at the top so it could vent the pressure there, and of course this meant there was always a film of oil mist all over the engine compartment!  This was entirely due to the PCV system being closed off.

So please understand why that green air/oil separator is there, why it is a service item every 30,000 km, why it is important that the tiny hole in the connect is clear, and please don't vent your crankcases to atmosphere.

Roy

[roy4matra]

I've been looking at in here now, and really can not see that there is any way that the arm on the OVAD valve (Ouverture du volet après départ à froid) can be can be activated by the gas,- or choke linkage.

That small diaphragm on the carb. operates the arm sticking out of it.  All that happens is that when you pull the choke out fully, the strangler flap at the top closes restricting air intake.  When the engine fires it needs more air and the high vacuum created in the inlet causes the diaphragm to pull that rod back and pulls the strangler flap open to allow more air in.  Try it manually without the engine running.  Open the choke fully and you will see the strangler flap on the top close.  Now look at the bend at the end of the rod from the diaphragm.  It is close to the strangler linkage.  As soon as the rod is pulled back the bend at the end will move the linkage and open the flap.  It doesn't need any return spring or other connection, it is simply pulled back by the diaphragm and returns to its rest position when the diaphragm relaxes as the vacuum drops.

Roy

[RazorbackNOR]

But back to the engine problem...
What would cause the backfires up the carburator?

As a general rule, backfires in the intake are caused by weak mixtures and backfires in the exhaust are caused by rich mixtures, providing everything else is correct.

Roy

Roy, how would you say the timing looks set on my car?

Can't imagine why it should be running weak now... have blocked of the vacuumpoints on the intake manifold, the accelerator pump diaphragm has been replaced and checked that it does works now(looked down the carb as it backfired and scared me shitless...)

Possibley switched the main jets? Any other suggestions?

[roy4matra]

But back to the engine problem...
What would cause the backfires up the carburator?

As a general rule, backfires in the intake are caused by weak mixtures and backfires in the exhaust are caused by rich mixtures, providing everything else is correct.

Roy

Roy, how would you say the timing looks set on my car?

That timing looks spot on 10 degrees, so it is probably not the timing that is the cause of the backfire.  You are still using the original Solex 34CIC carburettor?

Possibley switched the main jets? Any other suggestions?

I need to know more about your engine and set up first.  Is the engine standard or bored out?  What is the camshaft, standard or tuned?  Have any mods. been done to the carb.  Have you checked the engine when running with either a vacuum gauge or oscilloscope?  Particularly if the camshaft has been modified, has the valve timing been checked?  These and other things can all affect the engine running.  Forgive me if you have mentioned the set up before in the threads on this forum but I don't want to have to trawl though many pages just to see if the info is there anywhere.  It could take a looooong time. :-)

Roy

[RazorbackNOR]

But back to the engine problem...
What would cause the backfires up the carburator?

As a general rule, backfires in the intake are caused by weak mixtures and backfires in the exhaust are caused by rich mixtures, providing everything else is correct.

Roy

Roy, how would you say the timing looks set on my car?

That timing looks spot on 10 degrees, so it is probably not the timing that is the cause of the backfire.  You are still using the original Solex 34CIC carburettor?

Possibley switched the main jets? Any other suggestions?

I need to know more about your engine and set up first.  Is the engine standard or bored out?  What is the camshaft, standard or tuned?  Have any mods. been done to the carb.  Have you checked the engine when running with either a vacuum gauge or oscilloscope?  Particularly if the camshaft has been modified, has the valve timing been checked?  These and other things can all affect the engine running.  Forgive me if you have mentioned the set up before in the threads on this forum but I don't want to have to trawl though many pages just to see if the info is there anywhere.  It could take a looooong time. :-)

Roy

Yes, still using the original one. No modification has been done to it as far as i know, other then replacing the gaskets and diaphragms.
Engine is standard, again, as far as i know, since i would believe that previous owners would have informed if there had been any modification.
Camshaft should be original also. As far as i know, no major modifications or other works has ever been done to the car, so should be original with regards to the engine.
One thing thou, probably nothing to do with these problems, but my temprature sensor is busted.
i don't have a vacuum gauge or oscilloscope, so it has not been checked with that.

[roy4matra]

Yes, still using the original one. (carb.) No modification has been done to it as far as i know, other then replacing the gaskets and diaphragms.
Engine is standard, again, as far as i know, since i would believe that previous owners would have informed if there had been any modification.
Camshaft should be original also. As far as i know, no major modifications or other works has ever been done to the car, so should be original with regards to the engine.
One thing thou, probably nothing to do with these problems, but my temprature sensor is busted.
i don't have a vacuum gauge or oscilloscope, so it has not been checked with that.

(Please note I have updated this slightly 17th May)

O.K. thanks for updating me.  I have to say that it surprises me that you have an engine so original and standard as so many have been uprated, but that is just a comment not a criticism.

Now with regard to the backfire I have to say that since the timing looks just about spot on, and certainly not inaccurate enough to cause a problem, and with everything else just about standard, it leaves only one conclusion - it suggests the mixture must be weak, so that means either there is insufficient fuel or some additional air is getting in somewhere.  I'm assuming the basics have been checked and all the compressions are good and the valve clearances are correct?  If not then you need to do this since you could for instance have a valve not sealing on its seat and causing problems.  You mention changing jets in the carb. but if it is original and nothing has ever been altered then why would you have to do that?  It worked originally so it should still be correct.   No, the problem is something has changed from when it ran correctly, so you have to find out what has changed and repair it.

Oh one more thing I have just remembered I needed to ask.  What grade fuel are you running?  Any standard 2.2 Murena should be running the high octane fuel i.e. 97 or 98 octane.  The normal (in Europe) 95 octane is not good enough.  Whilst it may not be the cause of this backfire, you will get 'pinking' or pre-ignition with it and this can cause detonation, which can easily be mistaken for pre-ignition but is so damaging that it can melt holes in pistons and generally ruin an engine.  It is simply not worth the risk.  If you cannot get the high octane version where you are, then please make sure you use some Octane booster additive in your fuel.  I have run six 2.2 engines over the last thirty plus years since 1983 and not one has run cleanly on 95 octane, so although I have heard others say they have, I'm sorry but I don't trust that information.

I know that in one case of someone saying that he ran 95 and it was fine - when I was in that car I could hear the pinking and when I pointed it out, his comment was 'Oh is that what that is'!  So his comment about the car running fine on 95 was not true - it was just he did not realise it was not running correctly.  He was lucky he had not done any damage.  There is one other thing regarding this - if you drive the car really gently you may not experience the level of problem this causes, but I don't understand anyone buying a Murena and then driving it that 'gently'.  It is a sports car and a great one at that, and I certainly drive mine like a sports car which means quite hard and fast at times when conditions allow.  I still use full revs when required.  Age is not a reason to treat these any different - provided the car is maintained properly it is just as capable today as it was originally.

So back to the problem.  The reason I asked about whether you had used a vacuum gauge is that these can be quite a cheap and easy to use tool which can easily point to problems.  Another useful tool can be the Colourtune plug, although with the position of the plug holes and the engine in the Murena these are not easy to use in this particular application.  Whilst you said you have blocked all the vacuum connections off so none of those could be the cause, what about the inlet manifold?  Have you removed and checked the gaskets?  You could have a small air leak past a failed gasket between the manifold and head?  Or between the carb. and manifold.  Or the manifold itself could have a tiny hole or small porosity - it is after all an aluminium casting and these can sometimes be porous.  When was the last time it ran properly and what has been done since that time?  It is when things are done that changes occur and problems can start because of those changes or something else that happened inadvertently.

Have you had an exhaust emission CO test reading recently on the engine?  Since these engines use carburettors, the CO level should be around 2.0% - 2.5% at idle and the HC ppm level should be around 150-200.  Modern fuel injected engines might manage 0.5% CO or lower but you never want to try to get anywhere near that level with a Murena (or any carb. engine)  It is simply too weak and will lead to damage.  The European test level acceptable for this age and type of engine is actually 3.5% max CO and 1200 ppm HC. and the Murena can easily pass this test as 3.5% is quite rich and any figure greater than say 350-400 ppm HC would also point to a problem for this standard engine.  If any European country tries to impose a tighter level than these engines are capable of, then they are being stupid.

So if you have some CO/HC readings I would be interested to see the results.

The only other thing I can think of at this moment is that if the cut in the flywheel is in the wrong place it could mislead as to the the correct timing.  Now if the engine has never been apart so the flywheel is still original and fitted in the original place, it must be correct.  But you should be able to double check this anyway as I had to do once on a 2.2 in someone else's Murena.  Since this engine was originally in the Tagora 2.2 and is based on the Chrysler 180/2-litre which were all front engined cars, the original timing case marks are still on the engine.  They may not be so easy to get at but you can check them.  The lower timing case has the timing marks cast into it near the crankshaft pulley, and the pulley should have the small notch in it.  So if you line this notch up with the 10 degree mark on the timing case, you should then find the cut in the flywheel is lined up with the 10 degree mark on the clutch bell housing.  If it is not then there is a problem!

Roy

[Oetker]

I also had pinging on lean mixtures with some fuels so I stay on super 98.
That's in my opinion also recommended and several user manuals say it's needed.
Later some story's appeared that the 2.2 can handle the lean mixtures like 95 but that's not my experience to.
Also take care not to put in the new fuels (E5+ - E10+), there is (m)ethanol added and it can kill your engine.

There is a easy trick to find out if the inlet manifold is leaking by spraying a little engine cleaner around the seal of the manifold.
If the engine at idle runs a bit higher rpm when you spray,  then the seal has a leak there.


The 2 vacuum hoses are gone in my 2.2
I made a vacuum system with a UP 28 Hella  Volvo pump.
No more leaking on my manifold and better brake power is the rewards of doing so.

The 1.6 can handle Euro 95 fuel very good.
No need to go for other fuels in there.

Herman

[RazorbackNOR]

Yes, still using the original one. (carb.) No modification has been done to it as far as i know, other then replacing the gaskets and diaphragms.
Engine is standard, again, as far as i know, since i would believe that previous owners would have informed if there had been any modification.
Camshaft should be original also. As far as i know, no major modifications or other works has ever been done to the car, so should be original with regards to the engine.
One thing thou, probably nothing to do with these problems, but my temprature sensor is busted.
i don't have a vacuum gauge or oscilloscope, so it has not been checked with that.

(Please note I have updated this slightly 17th May)

O.K. thanks for updating me.  I have to say that it surprises me that you have an engine so original and standard as so many have been uprated, but that is just a comment not a criticism.

Now with regard to the backfire I have to say that since the timing looks just about spot on, and certainly not inaccurate enough to cause a problem, and with everything else just about standard, it leaves only one conclusion - it suggests the mixture must be weak, so that means either there is insufficient fuel or some additional air is getting in somewhere.  I'm assuming the basics have been checked and all the compressions are good and the valve clearances are correct?  If not then you need to do this since you could for instance have a valve not sealing on its seat and causing problems.  You mention changing jets in the carb. but if it is original and nothing has ever been altered then why would you have to do that?  It worked originally so it should still be correct.   No, the problem is something has changed from when it ran correctly, so you have to find out what has changed and repair it.

Oh one more thing I have just remembered I needed to ask.  What grade fuel are you running?  Any standard 2.2 Murena should be running the high octane fuel i.e. 97 or 98 octane.  The normal (in Europe) 95 octane is not good enough.  Whilst it may not be the cause of this backfire, you will get 'pinking' or pre-ignition with it and this can cause detonation, which can easily be mistaken for pre-ignition but is so damaging that it can melt holes in pistons and generally ruin an engine.  It is simply not worth the risk.  If you cannot get the high octane version where you are, then please make sure you use some Octane booster additive in your fuel.  I have run six 2.2 engines over the last thirty plus years since 1983 and not one has run cleanly on 95 octane, so although I have heard others say they have, I'm sorry but I don't trust that information.

I know that in one case of someone saying that he ran 95 and it was fine - when I was in that car I could hear the pinking and when I pointed it out, his comment was 'Oh is that what that is'!  So his comment about the car running fine on 95 was not true - it was just he did not realise it was not running correctly.  He was lucky he had not done any damage.  There is one other thing regarding this - if you drive the car really gently you may not experience the level of problem this causes, but I don't understand anyone buying a Murena and then driving it that 'gently'.  It is a sports car and a great one at that, and I certainly drive mine like a sports car which means quite hard and fast at times when conditions allow.  I still use full revs when required.  Age is not a reason to treat these any different - provided the car is maintained properly it is just as capable today as it was originally.

So back to the problem.  The reason I asked about whether you had used a vacuum gauge is that these can be quite a cheap and easy to use tool which can easily point to problems.  Another useful tool can be the Colourtune plug, although with the position of the plug holes and the engine in the Murena these are not easy to use in this particular application.  Whilst you said you have blocked all the vacuum connections off so none of those could be the cause, what about the inlet manifold?  Have you removed and checked the gaskets?  You could have a small air leak past a failed gasket between the manifold and head?  Or between the carb. and manifold.  Or the manifold itself could have a tiny hole or small porosity - it is after all an aluminium casting and these can sometimes be porous.  When was the last time it ran properly and what has been done since that time?  It is when things are done that changes occur and problems can start because of those changes or something else that happened inadvertently.

Have you had an exhaust emission CO test reading recently on the engine?  Since these engines use carburettors, the CO level should be around 2.0% - 2.5% at idle and the HC ppm level should be around 150-200.  Modern fuel injected engines might manage 0.5% CO or lower but you never want to try to get anywhere near that level with a Murena (or any carb. engine)  It is simply too weak and will lead to damage.  The European test level acceptable for this age and type of engine is actually 3.5% max CO and 1200 ppm HC. and the Murena can easily pass this test as 3.5% is quite rich and any figure greater than say 350-400 ppm HC would also point to a problem for this standard engine.  If any European country tries to impose a tighter level than these engines are capable of, then they are being stupid.

So if you have some CO/HC readings I would be interested to see the results.

The only other thing I can think of at this moment is that if the cut in the flywheel is in the wrong place it could mislead as to the the correct timing.  Now if the engine has never been apart so the flywheel is still original and fitted in the original place, it must be correct.  But you should be able to double check this anyway as I had to do once on a 2.2 in someone else's Murena.  Since this engine was originally in the Tagora 2.2 and is based on the Chrysler 180/2-litre which were all front engined cars, the original timing case marks are still on the engine.  They may not be so easy to get at but you can check them.  The lower timing case has the timing marks cast into it near the crankshaft pulley, and the pulley should have the small notch in it.  So if you line this notch up with the 10 degree mark on the timing case, you should then find the cut in the flywheel is lined up with the 10 degree mark on the clutch bell housing.  If it is not then there is a problem!

Roy

Hmm, have not checked the compression or valve clearance, not that much engine tools at my disposal, and the are VERY few and ridicloiusy prices shop that do this kind of work back here.

Shit, not that you mention it, I think it might actually have a can of 95 octan on it now, gone have to see if I can get some 98(although unleaded) on it pronto.

A vacuumgauge can easiely be purchased, so I should be able to get some things checked with it, any spesific points you want investigated?
Thought I might do as Oetker suggested to check for any leakes around the carb and inlet manifold.

I'm not sure when the last time it ran normally was, actually... I purchased it for bhavers here on the forum, but since he is a english sportscar fanatic, he couldn't be bothered to fix it, and sold it to me. Will se it I might be able to track down the owner befor him, and see what he remembers.

I do not have have a emission test on the car, and I do not know if any old ones from when the car was running have been kept either( and God know which workshops did it back then.

Will also checked the thigs you asked on the PM.

[roy4matra]

Hmm, have not checked the compression or valve clearance, not that much engine tools at my disposal, and the are VERY few and ridicloiusy prices shop that do this kind of work back here.

Ah, in that case all the basics need to be checked first.  It's no good trying to cure a fault looking at secondary things when you don't even know if the basics are correct.  If for instance you have an inlet valve not sealing, then the compression will push those gasses back into the inlet and that could be the reason for the ignition in the manifold. The reason I asked if a vacuum gauge had been used is that this can show up a problem here very quickly.  If the manifold is 'air tight' so the only air/fuel is coming through the carb., when idling, the vacuum reading should be around 21" Hg but if the inlet is leaking then the vacuum reading will be lower and show that it is not air-tight.

Shit, not that you mention it, I think it might actually have a can of 95 octan on it now, gone have to see if I can get some 98(although unleaded) on it pronto.

A vacuumgauge can easiely be purchased, so I should be able to get some things checked with it, any spesific points you want investigated?
Thought I might do as Oetker suggested to check for any leakes around the carb and inlet manifold.

I'm not sure when the last time it ran normally was, actually... I purchased it for bhavers here on the forum, but since he is a english sportscar fanatic, he couldn't be bothered to fix it, and sold it to me. Will se it I might be able to track down the owner befor him, and see what he remembers.

I do not have have a emission test on the car, and I do not know if any old ones from when the car was running have been kept either( and God know which workshops did it back then.

Will also checked the thigs you asked on the PM.

Also, we know these camshafts can wear badly if good oil was not used and regular servicing has not been done.  Or if the cam was re-profiled but the rockers were not replaced or refurbished at the same time that will cause excessive wear and premature failure.  Another fault I have found with all the engines from other peoples cars that I have stripped is that some of the rocker arms are not even in the correct places - the exhaust ones have oil holes and the inlet arms do not, but I have found them on the wrong side which will also lead to premature wear.  So when you take the cam cover off to check the valve clearances (which must be correct before you test the compressions) you first need to examine the rocker arms to check they are in the right places and check the camshaft lobes.  In fact if you send me a photo of the cam so I can see what it looks like it would be useful.

Roy

[RazorbackNOR]

Been thinking about doing some more work on my now ageing Murena. Since last, the starter i now busted in some way, no reaction whatsoever when turning the key, so probably have to remove it. Remenber from last time I tried(and gave up) that I didn't seem to get the bolt loose.... Any ideas on how to access the bolts and be able to get enough momentum on them to turn? Seem to remember a long-arm was impossible to fit....

[GP]

Been thinking about doing some more work on my now ageing Murena. Since last, the starter i now busted in some way, no reaction whatsoever when turning the key, so probably have to remove it. Remenber from last time I tried(and gave up) that I didn't seem to get the bolt loose.... Any ideas on how to access the bolts and be able to get enough momentum on them to turn? Seem to remember a long-arm was impossible to fit....

A short ring spanner or socket with short flexible head arm then a piece of pipe over the end to apply some leverage on may work.

[RazorbackNOR]

Been thinking about doing some more work on my now ageing Murena. Since last, the starter i now busted in some way, no reaction whatsoever when turning the key, so probably have to remove it. Remenber from last time I tried(and gave up) that I didn't seem to get the bolt loose.... Any ideas on how to access the bolts and be able to get enough momentum on them to turn? Seem to remember a long-arm was impossible to fit....

A short ring spanner or socket with short flexible head arm then a piece of pipe over the end to apply some leverage on may work.

Seem to remember a was able to fit both a spanner and ratchet with pipe pointing down, but not able to turn it at all, due to all other parts around, and fitting it pointing upwards meant that not able to use a piece of pipe for leverage....

[GP]

Looking through my toolbox I seem to remember that I may have definitely, possibly, maybe? used a crescent curved ring spanner (plus a pipe) to undo the nut and bolt.

http://www.ebay.co.uk/itm/FACOM-57-19x22-HALF-MOON-CRESCENT-CURVED-SPANNER-WRENCH-19-x-22mm-/131113344992?hash=item1e86f6dfe0:g:rcUAAOxy63FS93k3