what could be problem...!! & What to replace ?

Greetings to all experts,
Well, I am new to group & MB, I got a MB 260 (6 cylinders 2.6 Liter engine) automatic model 91, with 130K KM odometer. Basically this MB
came from Germany to a hot climate (Environment).
I replaced most of the filters and oil seals before I start using.
The following problems are noticed:
1.) Less gas consumption only 6KM per liter @ 120 KMPH, what is the actual mileage supposes to give?
2.) Black smoke layer forms at exhaust (end of the silencer pipes) no smoke visible.
3.) In Economy mode engine stop at signals, standard mode no engine stopping.
4.) Fuel indicator after middle of the tank it vibrates (up & down) not stable.
5.) Some times long start (time).
6.) When I start early morning there will be tick, tick... sound for a while.
When I show to mechanic he said all these indication leads (needed) to replace fuel injectors, I replaced 6 injector's nozzles and rubbers but the consumption remains same 6 KMPL. Long start problem seems to reduced, how do I know the old injector are good/bad?
I shown to other mechanic he is telling me to replace fuel distributor (repair kit).
I shown to another mechanic he suggested me to replace/cut the heat boosters in the exhaust tube (silencer), according to him in German environment need heat (temp) holder some kind of ceramic conduction material which holds the temp. all your comments & advices highly appreciated. Thanks in Advance
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Friend wrote:

10,3 litres/100 km at 120 km/h So roughly 1 litre each 10 km.
Juergen
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The engine burns too much fuel. The soot on the rear of the car is from unburned fuel and will cease when the underlying problem is corrected.
The possibilities in order of simplicity and expense are:
Worn out spark plugs waste fuel. Have you replaced the engine's spark plugs?
The engine should operate at 80 degrees C. After driving 5km the engine's temperature gauge should read no less than 80 degrees C. If not, the engine's cooling thermostat should be replaced so the engine no longer runs too cold, even in your hot climate.
The engine's ignition timing may be retarded - sparking too late to develop full power from the fuel.
Engine stalling is due to its poor running condition - fix the condition and the stalling will cease.
Ticking upon cold start is from a hydraulic valve lifter. Your new oil, and driving the car, will eventually cure this. Not important.
The fuel gauge's sending unit in the tank may be sticking from fuel deposits - or is defective. Add a can of carburetor or fuel injector cleaner to the fuel tank to dissolve the deposits (or confirm that the sending unit should be replaced).
These are symptoms of a somewhat neglected car or of a car that was not driven much. Your regular use will cure most of the problems.
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Don't know in euro... sorry can't help here...

Can be two things... unburned fuels or burned oil.

What is the engine RPM when in gear? While idling?

Tend to be the fuel level sender going bad or poor contacts.

Let's say after engine is hot and you come back in 15 minutes... long time to start? It would most likely be your fuel accumulator... it is supposed to maintain fuel pressure so gas don't turn into vapor above the engine area... which cause vapor lock.

Valve sound? I lived with mine for long time. Changing to thicker oil will quieten it up... or try synthetic oil for a while... and let it works its magic to clean up the gunks inside your engine.
Fuel injector rarely go bad... and if dirty, we just run fuel injector cleaner via gas tank... You got some real bad mechanics out there... probably those who don't specialize in MB... bad mistakes.
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Thanks for all your advices & recommendations,
Yes, I replaced all 6 spark plugs & mechanic tested after 2 months there is no oil or not black (not wet), I am sorry for poor terminology.
The engine shows less than 80 C even for 1 or 2 hours driving (night time), only when I drive more than 150 KM in mid of the day. The Temperature reading shows 80 85, my car temperature never goes to 100 degree even I drive 500 KM non stop (mid day).
When I brought my car, AC fan always running continuously, one of the mechanic said due to AC fan connected directly, recommended to install temp sensor. I buy a sensor and AC fan connected through it. Now AC fan will work only when I switch on AC or fan will start after / at 85Degree C temperature. is it the same sensor you are asking about? if not let me know.. pls. Yes, in my area there are no good mechanics for MB, but they tunes engine many times but no effect.
Yes, Mr. Tiger my engine oil level getting low approx 0.5 liters for every 1000 KM. I am adding every time the engine oil.
The Engine Idle RPM in gear around 700 RPM. (I think both are same or may be 600 in neutral)
After replacing (may be) new injectors the start problem seems to reduced.
Let me know if need more information.
Once again thanks for your time & involvement.
Have a nice time
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Sounds like your engine is normal running now. The hard starting I believe is your hot engine hard starting... it is faily common when fuel accumulator go bad.
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The engine shows less than 80 C even for 1 or 2 hours driving (night time), only when I drive more than 150 KM in mid of the day. The Temperature reading shows 80 85, my car temperature never goes to 100 degree even I drive 500 KM non stop (mid day).
Engine is running too cold - replace the engine thermostat.
The 2.6L six engine is known to have valve seal problems. The valve seals are plastic caps that fit over the valve guides in the engine's cylinder head. The valve stem slides up and down inside the seal - it is what is being sealed. These plastic seals wear out and allow engine oil to be sucked into the engine. The seals can be replaced by a skilled mechanic without removing the engine's cylinder head. If not repaired the oil consumption will slowly increase but the engine will not suddenly fail - unless it runs out of oil.
Engine's fuel injection air / fuel ratio can be adjusted, your engine seems to be set to be too rich - too much fuel.
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This forum have a problem there were 7 messages and I asked new questions all of them disappear, so just I am putting few lines of our earlier conversations.
-------------------------------- Mr. T. G Lambach said as follows -------------------------------- Engine is running too cold - replace the engine thermostat.
The 2.6L six engine is known to have valve seal problems. The valve seals are plastic caps that fit over the valve guides in the engine's cylinder head. The valve stem slides up and down inside the seal - it is what is being sealed. These plastic seals wear out and allow engine oil to be sucked into the engine. The seals can be replaced by a skilled mechanic without removing the engine's cylinder head. If not repaired the oil consumption will slowly increase but the engine will not suddenly fail - unless it runs out of oil.
Engine's fuel injection air / fuel ratio can be adjusted, your engine seems to be set to be too rich - too much fuel.
------------------------------------
1.) well, I will Replace the Engine Thermostat, if you can adive me right thermostat for my 260/ 6 cylendar / 91 model it will be great. I came to know there are different types of thermostats.
2.) as you said to replace the plastic caps is it require any special tool? let me know, I would like to know from you correct part numbers of plastic caps which fit over the valves.
3.) I ask my mechanic to adjust fuel injection Ration Air/fuel
to discuss or explain my mechanic I need more details for the following --
4.) what to to & how to do -----The engine's ignition timing may be retarded - sparking too late to develop full power from the fuel.
5.) what to do & how to do -- Engine stalling is due to its poor running condition - fix the condition and the stalling will cease.
6.) you can adivce all the areas which ever involved in getting full fuel consumption. (I mean to get 6 KMPL to 10 KMPL)
Thanks in advance, have a good time
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80 degree C is the only thermostat you should use... factory spec.

This is a major job. With whichever cylinder you are working one to top dead center of compression cycle (both valve closed). You need a air compressor to keep the valve up via an spark plug adapter that let you pump air in. The compressor must be on or if the pressure drop, then the valve will fall into the cylinder... but mainly you need the valve up so you can put the valve spring retainer pins in... you will need special valve spring compressor... In essence, a major work.

You have a hole in the middle of air filter housing... with a 3mm allen key, you can adjust the air/fuel mixture. With the allen key in the hole... push down and turn a bit to engage the gear... clockwise to enrichen mixture... other way to lean it out...
You have to do this with engine running and at operating temperature. You turn only 1/8 of a turn at a time... you can lean it out to the point where engine starts to run rougher... and back off.
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On Mon, 31 May 2004 18:31:44 GMT, "Tiger" wrote:

Be careful doing this - pressing down on the allen key whilst adjusting will cause a false adjustment. A light touch is needed for this and only do it once the engine is well up to running temp. If you can beg, borrow or blag a go on an exhaust analyser then that's really the way to go for these adjustments (in the UK any garage that does MOT tests has one of these).
300 Essie
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