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  #16  
Old 09-26-2008, 07:53 AM
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Are you in Australia? . If the answer is yes,then i suggest you change servo's because it's very probable that you have been sold 89-94 octane as 98. It's a common thing in Australia because there is no way to check the fuel we are sold.
I just spent a couple of weeks travelling around OZ in my 6.3 and more than once I filled with alleged premium unleaded only to find the car was pinging like crazy.
There is only one cure. Add 1 liter of ATF to every 100 liters of fuel.
then,drive the wheels off the car!.The ATF not only lessens pinging,but cleans out the MFI and the injectors.
Pinging can be caused by several other things besides fualty ADVANCE /RETARD MECHANISMS.

First thing to do is fit the coldest plugs you can find .
Next ,check the thermostat and make sure it's opening at the temp stamped into it.
Flush the block and radiator to make 100% sure the cooling system is working properly. With the engine running and up to temp,the water should be seen moving across the radiator
Change the aircleaner element to make sure the cool air is getting to the engine.You'll notice Mercedes was decades ahead of the game with the aircleaner snorkle in front of the radiator instead of sucking in hot underhood air.
Check the crankcase breather pipe is clear.
make sure the fuel pressure is 14PSI and no more. Over pressure causes all sorts of drama with a MFI system.
Make sure the plug leads and the plug ends are Mercedes type,not elcheapo silicon colored leads which have far too much resistance. if you have the original type ,run a multimeter over them to make sure the Ohms are not too high.
If you know anyone with a CO tester ,check the mixture underload at 60 kmh. If it's too lean you will get pinging because everything will be getting damn hot but not showing up as a hot engine on the gauge.

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  #17  
Old 09-28-2008, 04:59 AM
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hi guys

i have done a compression test with these results, from one to six

170 180 150 165 170 170

is this too high? i know the 150 is a bit low compared to the others, but are the figures high enough to cause pinging?



Quote:
Originally Posted by ja17 View Post
Hello,

I second Arthur's suggestion, "what is the compression". Since the head has been re-conditioned, the compression may be the issue.

Cold starting systems on these cars can be quite complex, but most likely not related. We can get into this later.

Injection timing is usually not resposible for these kind of issues with this type of injection system.
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  #18  
Old 09-28-2008, 10:20 AM
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Hello,

These readings seem a bit high for this engine. Are these figures on a warm or cold engine? On a warm engine they will be even higher. Notice how high the readings are on the end cylinders. This can be an indication that the head has been "cut" quite a bit, possibly beyound specs. When a head is warped from oveheating, it arches up in the middle. Afterward when it is "cut", most of the material is removed from the end combustion chambers to flatten the head again. This decreases the volume of the end combustion chambers and causes the high compression situation in those cylinders.

Do you have the repair records for this engine?
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1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #19  
Old 09-28-2008, 06:48 PM
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Would n't the cam be a bit tight? if the head was planed too much and it was warped enough to cause that sort of discrepancy the cam won't turn.
Often the valves being remachined will be enough to give different readings like that afterall the valve head takes a lot of combustion chamber volume.
I don't think it's too high ,which is why I'm sticking by the suggestion the Fuel is too blame ,along with the plugs being too hot,again the highish comp.readings can be off set with colder plugs.
Also,has the cam timing been checked accurately?
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  #20  
Old 09-28-2008, 07:53 PM
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hi guys

i removed all the tappet fingers and found the cam shaft turns easily so i dont think it is warped.

the valve timing is set so that at TDC the edge of the cut in the washer lines up with the left edge of the dimple (standing in front of the engine). to go a tooth the other way puts the timing way out but a mechanic i spoke to says its ok as it is.

its running NGK BP5ES.

i will try filling up from another source.

something else of note, when i drained the excess oil from the IP the pinging seemed to get worse. maybe the mixture is too lean?
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  #21  
Old 09-28-2008, 08:24 PM
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You set/align the cam index and then look at the damper to see how far off TDC it is..not the other way around. You can then rectify the offset caused by the head planing with an offset cam gear key.

If the oel level was too high it would cause a rich running condition..which means someone may have tried to correct for that richness by taking shims from the pump thermo or tightening the baro compensator, not realizing the incorrect oel level condition .Then when you corrected the oel level, the car would then go lean b/c of their other compensations...my suggestion would be to read the plugs [ look for white insulators as lean indication]..also power loss under load and possible high coolant temp.
You may also want to try opening the intake valves lash a few thousands and see if the results are better, just as a test .
A vac gauge may also help in diagnosis..
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  #22  
Old 09-28-2008, 08:57 PM
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Ok,two problems I can see already,As Arther quite rightly says,the cam needs to set correctly with a off set key. These engines run quite radical cam timing compared with their contemperys .BP5ES plugs are very hot . NGK's go opposite to normal with their plug ratings so a cooler plug is a 6 or 7 .
Hot plugs such as 5's are OK with a oily or rich running engine as a stop gap. Put them in a high comp engine with poor fuel and you will have preignition.
The idle mixture is independent of the running mixture so increasing the fuel at idle will not cause the engine to enrichen at higher revs. This can only be achieved by altering the throttle position.
Quite Possibly the throttle is out of adjustment.


So,if it were my engine I would start by getting the cam timing perfect.(Have you replaced the chain?)
Then make 100% sure the ignition is perfect with #7 plugs as a starter.
Next,the throttle position would be checked and then a test with a CO tester to ensure it's not too lean under load .
With good fuel preignition should be at minimum.
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  #23  
Old 09-29-2008, 03:05 AM
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hi guys

just an update

i re-read the answers given (many thanks to all!) and should add the test results were with a hot engine.

i fitted BP7ES and filled it up with fresh 98 octane. there seemed to be an improvement, but it is still pinging.

i removed the atmospheric diaphragm/plunger and noted the shims/washers amount to 3.10mm. i thought one could have no shims, or 2mm if running lean?

also with the cam spocket washer notch to the left of the dimple (standing in front of the car) isn't the cam timing retarded? ie, wouldn't valve timing contribute to pinging if it were advanced?
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  #24  
Old 09-29-2008, 04:55 AM
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Don't worry about whether or not the cam is retarded or advanced,what matters is the notch lines up perfectly with a good chain.. Most mercedes mechanics have offset keys laying about so just ask one if you can borrow a few different ones.
Re the aneroid compensator; Put the shims etc back where you found them and leave the aneroid alone. the aneroid height is set on a test bench and will not have any bearing what so ever with the fuel .
As I said,the mixture is controlled by the throttle position.
You need a CO meter ,it's pointless messing around without one.
The lower mid range mixture can be adjusted on the govenor but unless you have the specific instructions to hand i won't bore you with details...besides you have already messed with the aneroid ,thats enough mischief for one day...ha ha ..
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  #25  
Old 09-29-2008, 10:33 AM
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Aneroid with effect fuel mixture across the board, same as the the thermo shims do.......
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  #26  
Old 09-29-2008, 05:53 PM
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I fully realize that Arthur ,but BOTH are things that the average,even the good ,mechanic should leave well alone and are not to be played with .
As they are set on a test bench using a dial test indicator they are set for the life of the pump.
Both manipulate the link arm in the pump and interfering with them is NOT the way to adjust the fuel mixture. that is the function of the rear screws on the governor and again this NOT something for the home mechanic to play with ,especially for someone without a CO meter or any idea of the function of the governor mechanism.
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  #27  
Old 09-29-2008, 06:02 PM
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I am quite aware on setting Bosch MFI systems...my point was simply that there MAY HAVE BEEN some unneeded adjustments made in error b/c they were not AWARE of the pumps oil over-fill..this incorrect adjusting could be the cause of the lean condition..that's all..... notice he said that ping was more pronounced after the oil level was corrected from over-fill ?????
so, we agree...back to normal settings is the word of the day.

I have been doing these for many years and I can tell you I have seen hundred upon hundreds of these car be screwed with b/c both the owner and mechanics did not even KNOW there was an oil reservoir or dip-stick.

...and it is common knowledge that both the baro setting is not in fact a life time setting...they wear and get out of calibration all the time...same as the thermo warm up does...that is why we do shim adjustments on old pumps
b/c they wear Rich.

I have a clear glass gar that I pull a partial vac on for testing baro and I can tell you that is not uncommon to find some of them that don't work at all.
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Last edited by Arthur Dalton; 09-29-2008 at 06:10 PM.
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  #28  
Old 09-29-2008, 08:29 PM
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hi guys

thanks for your help - i dont mean to step on anyone's toes.

i did a bit of reading on the SL site and after careful measurement of plunge, used a bolt in place of the compensator to play with mixture. for the purposes of diagnosis, i set it rich to the point of not idling properly, and yet, the pinging condition remained unchanged. i can always just refit the compensator and shims, no harm done.

if i stand in front of the car, if the notch on the cam washer is to the left of the pedestal dimple (ie, rotating the engine clockwise brings them into alignment), is the valve timing retarded or advanced?
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  #29  
Old 09-29-2008, 09:42 PM
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Looking @ engine from the front...... The engine runs CW, so if cam indicator alignment requires turning the crank CW past TDC for the cam to align. [ as I believe is what you suggest] , then the valve timing would be retarded.
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  #30  
Old 09-29-2008, 10:29 PM
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Hello,

Each timing chain link is equal to eighteen degrees. It is not unusual for the timing slot on the washer to be a bit late getting to the mark on the camstand. Chains become longer with wear. A slight cut on a cylinder head becomes twice as much slack on a chain.

Most of the time normal chain wear from miles or repairs does not make much difference. Unless it is just set wrong, I find it difficult to believe that this can be the problem.

These early engines had lower compression than the later M130 engines etc. Look on the cylinder head near the casting number on the spark plug side and you will see the actual compression ratio cast into the head. It should read 8.7 to 1 That's not much psi if you do the math. I am figuring around 140 to 150 lbs max, even with carbon build up.

Often times when a head is cut, they also cut the top to flatten everything out again to allow the cam to turn freely. The book suggests shims under the camstands if needed. My old MB shop manuals also state than off set keys usually "make no noticable difference" at least on these earlier engines.

Anyway you are probably going about it correctly. Check all the cheap fixes first. A new cylinder head would be pricey.

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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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