A curious noise coming from an overhauled engine

[GGR]

Also, make sure to never fiddle with the idle adjustment knob with the engine running, or you will damage the mechanism.

[watson2]

Also, make sure to never fiddle with the idle adjustment knob with the engine running, or you will damage the mechanism.

Thank you GGr. Every time the engine must be stopped before touching the pump's knob.

[watson2]

Excuse me if during the next discussion I'll use incorrect terms , but my technical english is even worse , if possible, than the not technical one.
Well guys. Against all odds , the behaviour of my mechanic has been very professional.
The car arrived to the workshop with a 5 cylinders idle. If I accelerated up to 2500 rpm the engine was running better, but just a few seconds later it returned to 5, if idling.

Manouvers and effects : removing the spark plug cap of the cylinders 6, 5, 4 the engine went with 4 cyl. The same with 1 and 2. But with the absence of the cap nr. 3 there were no changes. Always 5 cyl.
The spark plug was dirty,  black and with a lot of charcoal deposits .

New spark plug into cylinder nr.3. Starting again the engine , just in a few seconds  it was evident that nothing was changed : 5 cylinders again.
Then the wire nr.3 was tested and the spark of nr.3 was verified. If was strong.  No problem with ignition system.

So the attention moved onto the injectors.
 
The injector nr.3 was exchanged with nr.6. No changes . The cylinder that produced the 5 cyl rithm was always the nr.3.
So the injectors are not guilty.
Probably there is something into the injection pump the doesn't work correctly : the valve that guides the fuel spot is not closing correctly. It could remain opened.
The fuel  is too much. With idle rpm it  quickly gets the plug dirty.   With higher rpm the air/fuel ratio probably becomes less dramatically busted and the engine runs better.

We had a  suspect : the fuel filter was changed 1 week ago. There was some dust in the bottom of the cup of the filter and the filter was grey.
Opening again today the filter,  the thing was evident: a lot of powder in the bottom of the cup and the filter dirty.
Where is coming from all that powder?  From the tank , of course. Infact we kept off the sender and we looked into the tank. The surface was covered by that dust.
All this despite a treatment with a layer on the internal surface of the tank.
The treatment did not involve the part of the surface under the cup that so remained rusty.

Before changing the injectors a  Bardhal injectors cleaner was added in recent weeks and this has probably set in motion the rusty dust that was under the cup.
We have no other explanation considering that all metal and rubber hoses of the fuel lines are new.

Result: already ordered a new tank. I'm sick of this.
The pump will be cleaned and I hope to obtain , at last, an engine working fine.

[stickandrudderman]

A Co meter is only partially useful. An analyser that measures CO and HC is much better. You can have perfect CO but high HC (anything above 500 is cause for concern but around 200 is great) will indicate poor combustion.

[watson2]

A Co meter is only partially useful. An analyser that measures CO and HC is much better. You can have perfect CO but high HC (anything above 500 is cause for concern but around 200 is great) will indicate poor combustion.

Thank you Stick. I saw that this is a parameter present on the screen of the instrument used on my car.

But here we are to discuss again about fuel.

When you see , only one year ago , an environment like the one of the first picture, with a brillant and even elegant  white  , you can't imagine that only 12 months later all this can be transformed into a disaster like the one that you can see in the other pictures. Only when I saw the powder found in the filter's cup I surrended and I was compelled to think that all that nice white could have some problems. As a matter of fact ....
The coating is cracked and not adhering to the metal in many parts of the tank.
Probably the metal wasn't completely dry when the coating was positioned, because it seemed clean in the photographs that I saw one year ago.
The debris that you can see is only a fraction of the total and the last pic was made after a treatment with phosphoric acid just washed away a few minutes before.

[watson2]

By the way: I ordered a new tank to MB and the delivery is scheduled for september 23 !!! (of this year   ) . I suspended the order.
So I asked to Niemoeller and they will tell tomorrow a certain date of delivery (it will not be a date so close).

In the meantime we will treat the tank to get by while waiting.

[GGR]

A few years ago I did have my tank dipped into an acid bath and I then used the Por-15 fuel tank sealing kit. So far so good!

[watson2]

A few years ago I did have my tank dipped into an acid bath and I then used the Por-15 fuel tank sealing kit. So far so good!

Your tank met a serious person . My one , on the contrary , for 2 times, has met only stupid people.


Picture nr.1&2 = stupid nr.1   (Stones, sand and a perfect coating of the surface)
Picture nr.3     = stupid nr.2   (Fuel inlet of the 'tea pot' completely closed. The car worked only with 40 Lt. or more)

[Mike K]

When I needed to replace my fuel tank, the only dealer who was able to supply me with a new tank right away was Van Dijk:
http://www.classicsl.com/en/190sl-230sl-250sl-280sl-onderdelencatalogus/230sl-250sl-280sl-onderdelencatalogus/brandstof-onderdelen/

Give them a call if Niemoeller are unable to assist.

Good luck,
Mike

[GGR]

Your tank met a serious person . My one , on the contrary , for 2 times, has met only stupid people.

Well, I kind of did it myself. I took the tank to people who dip stuff into acid. They kept it a few days. Then they usually coat everything in oil to avoid flash rust. In my case I requested them no to do that and call me immediately when the tank was out. I then just applied the POR-15 sealing as per instructions given in the kit. Quite easy and cheap to do. You should give it a try.

[Benz Dr.]

You have to be very careful when having your tank adic dipped. I've seen where they came back spotless minus the flower pot. One of the pics above shows that very clearly, and, you can't replace it once it's gone. After the tank is acid dipped it has to be placed in a solution that will remove and neutralize all of that acid or you will have problems later down the road.
I won't coat fuel tanks. I've seen more ruined tanks than I've seen those that were helped. We boil them out in a mild caustic solution until they're clean. Junk ones get replaced with new or used tanks depending on what we have available. 

[Fintail]

Would there be a demand for a replica tank in plastic(as used in modern cars)

Kind regards

John

[watson2]

When I needed to replace my fuel tank, the only dealer who was able to supply me with a new tank right away was Van Dijk:
http://www.classicsl.com/en/190sl-230sl-250sl-280sl-onderdelencatalogus/230sl-250sl-280sl-onderdelencatalogus/brandstof-onderdelen/

Give them a call if Niemoeller are unable to assist.

Good luck,
Mike

Thank you , Mike.
Many, many thanks. I contacted them and they have the tank in stock.
Niemoller too was very precise and efficient, but they can deliver their tank in 3 weeks.
I'm in a hurry and so I ordered it in the Nederland.
I will let you know when it will arrive.

[Mike K]

Thank you , Mike.
Many, many thanks. I contacted them and they have the tank in stock.
Niemoller too was very precise and efficient, but they can deliver their tank in 3 weeks.
I'm in a hurry and so I ordered it in the Nederland.
I will let you know when it will arrive.

Excellent news Flavio! This was exactly my experience, Niemoeller were efficient but needed time & Van Dijk had the fuel tank in stock....

Best,
Mike

[Benz Dr.]

Would there be a demand for a replica tank in plastic(as used in modern cars)

Kind regards

John

You might imagine that there could be, however, the mounting of the tank would need to be changed. Only three nuts hold the tank in place on our cars and somehow I can't imagine that working out very well with a plastic one. Some sort of reinforcement would be needed.

[watson2]

You have to be very careful when having your tank adic dipped. I've seen where they came back spotless minus the flower pot. One of the pics above shows that very clearly, and, you can't replace it once it's gone. After the tank is acid dipped it has to be placed in a solution that will remove and neutralize all of that acid or you will have problems later down the road.
I won't coat fuel tanks. I've seen more ruined tanks than I've seen those that were helped. We boil them out in a mild caustic solution until they're clean. Junk ones get replaced with new or used tanks depending on what we have available. 

Yes, Benz Dr. You are right. I have not yet posted the image of the pot. Here it is. One year ago it was not in bad conditions. Now it's destroyed. In that tank was poured only one can of Bardhal injector cleaner during the last year. I cannot believe that it can perform this effect . It's easyer to think to the effects of not neutralized acid . To neutralize the acid could be enough a simple solution of sodium bicarbonate (NaHCO3) with water.
By the way : I checked the photographs that the 'stupid nr.2'  sent to me before performing the placement of the white cover. And curiosly the pattern of the detached cover that has been cut away in the 3381 pic here above, is similar to the one that you can see here (second pic ) . 
Rust , acid , holes stopping : how many mistakes in a single tank....

A note: the new tank is arriving from NL , but if my one was the last pot available all over the world, it would have been possible to rebuild it ( with resin or , more easy, with inox 1 mm. thick). There is nothing that cannot be reproduced.  And this is one of the simplest things to be reproduced.

[watson2]

Hi guys. The new tank is still traveling...  Nothing new to say about this...
But I wanted your opinion about this: we have seen in the previous messages that a plug ( the nr.3) goes quickly out of service with carbon deposits because the quantity of fuel in the cylinder nr.3 is too much.
I use this fantastic image of Joe Alexander ( thank you, Joe , for sharing, you are a great professor) to ask to you which could be the detail that remained open (it's probably dirty for the rusty powder of the tank).
Consider that the bracket  moves freely and all the other plugs are remarkably lean.

[ja17]

Hello Watson,

If just one cylinder is rich and fuel fowled, it could be the injector stuck open. Check the injector and try a new spark plug on #3.

[watson2]

Hello Watson,

If just one cylinder is rich and fuel fowled, it could be the injector stuck open. Check the injector and try a new spark plug on #3.

Thank you, Joe, for your message. An honor . No, the problem does not come from the injector. As I told in the message#102 (I understand , it was a little long... ) the mechanic verified that the 5 cyl idle was coming from cyl #3;  so a new sprark plug was tested on  #3 and in a few seconds it became dirty. Then the injector 3 was swapped with the 6. The problem remained on the cylinder #3. It was not the injector. The problem comes from the pump that seems to deliver too much fuel.

[watson2]

So guys , here we are ! The tank arrived from the Nederland and was installed. A little quantity of electric contact activator has been poured into the nr.3 exit of the injection pump ( into the part described as 'fitting' in the image of Joe Alexander, here above) .
The activator is enough to clean metal parts gently and it isn't too strong to damage metal parts.
A new fuel filter was installed and all the hoses of the circuit were washed with clean fuel (the old fuel had a strange grey shade; it will be good for my 11HP Simplicity to cut the grass).

With a 100 octane fuel (Shell V power is the only one here in Italy) the noise is now remarkably reduced. Some friends told me that this is the normal noise of the 230 and that if you want something a little quiter you must buy a 280.
The car has immediately changed behaviour. Now the engine has a good rithm, no uncertainties. Quite good.

The plastic of the 'tea pot' is white and quite different in comparison with the old one.  The new tank seems to be treated with zinc and the fuel hose is in copper. The return hose seems to be in stainless steel.  The choice of Zn + Cu is strange because these two metal could determine corrosion through a 'battery effect' (right word?).

Here some images of the details described above and the image of a strange jellow cream that is present on the exterior part of the pipe and seemed to be poured down into it.

[watson2]

So  I wanted to thank all the members that gave their opinion and helped me to solve the problem with all the messages that we exchanged.

The good thing of this  discussion is that I have known a lot of nice people and I learned a lot of new things.

Thank you all again, guys, sincerely .

[ja17]

Happy Motoring Watson!

[Garry]

Good outcome.

  It has been an interesting story watching it unfold and the twists and turns to finally work out the problem and have resolution.  Have watched with interest.

Enjoy the ride.

[watson2]

    Hi guys. It's me again.
There is an appendix to my story and I want to share it with you , if something can be useful for someone else.
Well, my noisy engine was not exactly what I expected to have. If the mixture was lean, the noise  was in some
way acceptable; but as it was necessary to enrich the mixture, the noise became stronger. So I found a friend
that was able to measure the compressione ratio with a reliable instrument.
The result is in the image that I attach : 11.75 was the value in two cylinders. we stop measuring. It was enough.

[watson2]

Tired with my first technician I went to a new mechanic to 150 km away from my house.
He inspected the car and he listened to the whole story and looked at the pictures with great attention.
He was going  to open the engine and then to tell me what could be done.
Some day after he called me and said that when he makes an engine he want to give warranty and to make this he was going to make again an overhaul, this time a complete one.
I don't show to you all the details with mistakes or defects he found.
I want to concentrate the attention to an aspect regarding the compression ratio.

We used a formula, universally accepted for the determination of the combustion chamber volume:
In normal conditions it's this :
                       volume of the chamber = single cylinder displacement/( compression ratio-1)
so VC = 384cc /(9,3-1)      gives  46,26 cc of volume in a normal , untouched combustion chamber.

But we have seen that we had a compression ratio of 11,75 and so the volume is reduced to 35,7cc
About 10,5 cc missing ...

I didn't want to buy a new head from Mercedes or other sellers and so the solution was found with
special pistons built in Torino with proper excavations to obtain the missing volume.
I attach an image of the pistons.