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Author Topic: Dan's 1.6 repairs  (Read 21471 times)
Grapes
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« Reply #180 on: June 06, 2022, 08:47:03 am »

By now I indeed have a tank of clean petrol. I'm going to see if the local guy here who helped me out last time can teach me to do the valve timi g. I will ask him if we can have a look at the original distributor as well. It is probably a good thing to have a backup if the electronic one ever breaks down.
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suffolkpete
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« Reply #181 on: June 06, 2022, 11:59:18 am »

I had my distributor overhauled by Ignition Car Parts of Basildon.  It came back looking like new and works perfectly.
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Grapes
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« Reply #182 on: June 08, 2022, 01:28:41 pm »

We're also going to have a look at the vacuum system first. Anything in particular I need to pay attention to or should I just try to find all the hoses and replace them first?
Also, is there any schematic for it or a list with the specs of the vacuum tubes I would need to buy? I tried looking in the manual but couldn't find a chapter on that.
I'm currently looking at http://www.matraclub.org.uk/faq8.html#top which seems to have most information on the subject I could find so far.
« Last Edit: June 08, 2022, 04:09:50 pm by Grapes » Logged
suffolkpete
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« Reply #183 on: June 09, 2022, 12:59:53 pm »

If you suspect the vacuum system, a quick way to test it is to blank off the connection from the inlet manifold and see if the running improves.  If it is suspect, then other considerations are the one way valve on the input to the reservoir, the diaphragm in the servo and the electrovalve on the left hand side of the front compartment.  For the tube, just buy it of the correct internal diameter off the roll.
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Grapes
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« Reply #184 on: June 30, 2022, 10:06:17 am »

Vac system isn't perfect in the sense that it still holds vacuum for days but I found one hose that was visibly older and cracked and changed it. Now at least the pods still come up after I stopped the engine for a few minutes which is already an improvement. Smiley

This didn't help the engine from stalling after driving for a while and I didn't dare to mess with the valve clearance yet since I don't have the tool mentioned in the manual.
For now I dialled in the idle screw on the carb as per the instructions in the manual so it idles around 950 on a warm engine.

One thing I do notice now is that it sometimes idles at 1000-1100 and doesn't go down for a while but for now it at least runs a lot smoother while I search for someone who has time and will to teach me in person how to set the valve clearance and properly check and configure the carb.
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roy4matra
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« Reply #185 on: July 02, 2022, 02:49:37 pm »

Vac system isn't perfect in the sense that it still holds vacuum for days but I found one hose that was visibly older and cracked and changed it. Now at least the pods still come up after I stopped the engine for a few minutes which is already an improvement. Smiley

OK that's good and hopefully removes any source of mixture weakening from air that has not past through the carburettor.

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This didn't help the engine from stalling after driving for a while and I didn't dare to mess with the valve clearance yet since I don't have the tool mentioned in the manual.
For now I dialled in the idle screw on the carb as per the instructions in the manual so it idles around 950 on a warm engine. One thing I do notice now is that it sometimes idles at 1000-1100 and doesn't go down for a while...

Was the rpm measured on the car rev counter or did you have a more accurate one connected?  The one in the car is notorious for being inaccurate and slow, so you cannot use it to set an accurate idle rpm.

Does the engine still have the original Weber 36 DCNVA fitted?  For an engine being slow to return to the set idle rpm, that often occurs owing to the throttle plate(s) not returning to the same position every time, and that is possibly due to slight wear in the spindles and mountings - it happens with many old engines.  You can even get a little air drawn in past the spindles.  Check for wear there.

Also if the float bowl fuel level is slightly high, a tiny bit of fuel can dribble across into the manifold and combines with the air to hold the revs from dropping to the set idle until it is used up.

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... while I search for someone who has time and will to teach me in person how to set the valve clearance and properly check and configure the carb.

I doubt you would get that tool 0016928200 mentioned in the manual for setting the valve clearances, today!  However you don't need it, all you really need is a set of feeler gauges, a small spanner to fit the adjuster and another to fit the locknut.  Plus the knowledge of how to adjust the valve clearances.

As for 'configuring the carburettor' - you can't configure it.  The Weber (or the Solex on the 2.2) are fixed jet type carburettors and once the jetting has been decided originally by the manufacturer, it stays like that unless someone starts fitting other jets!  The only adjustments you have are the idle stop screw, to set the idle revs, and a mixture screw which is badly termed in fact.  It does not alter the mixture of fuel and air, but simply allows more or less of the aerated idle mixture already set by the idle fuel and air jets.

So if the Weber is the original standard one fitted to the 1.6 engine, you simply set the idle, and then adjust the 'mixture' screw to give the highest rpm and then reset the idle screw again to bring the engine back to the correct idle.  What you are doing with the idle mixture screw is matching the amount of aerated fuel to the amount of air being drawn past the almost closed throttle plate(s).  (Only 1 throttle plate for the progressive twin venturi carbs. in either Murena 1.6 or 2.2, as the second venturi should be completely closed at idle; but there can be two or more throttle plates if the carbs. are simultaneous opening twins such as the twin side-draught Solex on the Murena 'S'.)

Roy
« Last Edit: July 02, 2022, 02:52:51 pm by roy4matra » Logged

suffolkpete
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« Reply #186 on: July 02, 2022, 05:22:05 pm »

The 36DCNVA carb I have has two throttle plates on a common spindle that open simultaneously and by equal amounts, also two idle screws that should be adjusted simultaneously to give the correct idle.
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Grapes
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« Reply #187 on: July 03, 2022, 02:00:27 pm »

Thanks for the input!

For now I used the car's rev counter. Any info on where to get and how to connect an accurate one on your website Roy? I couldn't find it on the FaQ section about vacuum and engine revs.

I'll have to have a close look to confirm with certainty but as far as I am aware my carb matches the 36DCNVA in the manual. 2 mixture screws and one idle. According to the manual instructions I first brought the warm engine to 950rpm with the idle screw, then I alternated turning the two mixture screws to get the rpm as high as possible and then bringing the rpm back to 950 with the idle screw. next I turned in the mixture screws in turn until the rpm dropped by 25 and then again adjusted with the idle screw. (I hope I have the right terminology because I'm translating from the Dutch manual and I'm not sure about the term they use for what I think is the idle screw.)

I have feeler gauges and spanner sets but I prefer to do the valve clearance under the watchful eye of someone who's experienced with it Wink
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roy4matra
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« Reply #188 on: July 03, 2022, 02:45:07 pm »

The 36DCNVA carb I have has two throttle plates on a common spindle that open simultaneously and by equal amounts, also two idle screws that should be adjusted simultaneously to give the correct idle.

Sorry, you are quite corret Peter, I was thinking of the DMTR Weber which is similar to the Solex on the 2.2 Murena.  Thanks for the correction.

And those two idle screws, are the ones admitting the aerated mixture from the idle air and fuel jets.  There is only one thottle stop screw.

Roy
« Last Edit: July 03, 2022, 03:00:06 pm by roy4matra » Logged

roy4matra
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« Reply #189 on: July 03, 2022, 02:56:46 pm »

Thanks for the input!

For now I used the car's rev counter. Any info on where to get and how to connect an accurate one on your website Roy? I couldn't find it on the FaQ section about vacuum and engine revs.

No, you won't find details such as these on my website, because these are in the basic knowledge that any mechanic or technician would know.  My website is not there to teach anyone basic mechanics.  It is provided to let experienced mechanics understand the Murena where there differences to other cars, which an experienced mechanic or technician may not have come across before.

An external accurate tachometer should be connected to the coil negative terminal of course.

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I'll have to have a close look to confirm with certainty but as far as I am aware my carb matches the 36DCNVA in the manual. 2 mixture screws and one idle...

No need to check, I was wrong and as Peter has stated, it is a simultaneous opening carburettor.  Apologies for my error.

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I have feeler gauges and spanner sets but I prefer to do the valve clearance under the watchful eye of someone who's experienced with it Wink

Fair enough, and correct when you are not aware or haven't done it before.

Roy
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Grapes
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« Reply #190 on: July 07, 2022, 11:41:30 pm »

Thanks! I can work with that Smiley
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