1977 350 sl misfire

[scott2gogo]

car stood for couple of years, i hve changed plugs,coil, leads,dist cap,rotor, drained old fuel, cleaned tank, new pump,filter, car runs , not good enough for the road, but then starts gradually misfiring till almost stopping, how much can one strip down the injection system, like the head where the fuel goes into, injectors, etc, any info or drawings be much appreciated or even better a good V8 man thats mobile in the hayes ,middx area , cheers ex merc bodyshop apprentice of 40 yrs ago

 

[meanie]

First thoughts are that the warm up regulator (part 270 in link below) has failed,causing it to run fully rich all the time.
http://www.detali.ru/cat/oem_mb2.as....701&VIN=*&CT=M&cat=042&SID=07&SGR=070&SGN=02
Should have 12v & an earth on the leccy connection.Easy to strip down.

At the other end of the scale,check the inlet system & all the rubber breather hoses for air leaks.

 

[Smudge]

Try new fuel, and fuel filter . You may find the old petrol has clogged the metering unit up as it will have gone stale after this period of time.

 

[television]

We had a post this morning on this and it turned out to be the cap

http://forums.mercedesclub.org.uk/showthread.php?t=49433

This is where the inline spark tester come into their own

 

[jibcl500]

Does she smoke at all? you can remove the bank of injectors whist still attached to the fuel rail, drivers side is easier than the passenger side and the throttle link needs to be removed as does the solid Y pipe in the valley, some other odds need removing too, worth removing though as the old injectors can leak and if they just push or drip fule through uncontrolled then it sounds and feels like a misfire.

Put a long screw driver on each injector and listen, they should ahave a good click to them and if ones not working well you will hear it.

Be aware new injectors are £282 each and Bosch dont make them anymore, MB only or used for about 60-80 quid each.

Seals can be bought from MB for pence and they do perish, the fuel rail has two regulators one for fuel in and one for fuel out.

Me i'd put £100 on the injectors being duff.... runs good when cold but once warm misfires.

jib

 

[vijilants]

We had a post this morning on this and it turned out to be the cap

http://forums.mercedesclub.org.uk/showthread.php?t=49433

This is where the inline spark tester come into their own

This is where a good old Crypton Tuner comes into its own

 

[roofless]

This is where a good old Crypton Tuner comes into its own

thats a blast from the past & very cheap now
http://cgi.ebay.co.uk/old-crypton-t...9|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

 

[vijilants]

thats a blast from the past & very cheap now
http://cgi.ebay.co.uk/old-crypton-t...9|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

The one with the scope is best...you hook up onto all the plug leads and the trace is shown on the scope as the car is running.....great for tracing and identifying an ignition misfire. Eliminates all the guesswork of is it fuel or ignition related.

 

[meanie]

JIBCL is referring to the old EFI system.By '77 it should be on the CIS system that I referred to.Can you confirm that this is the 'head' that you referred to in your original post.
http://www.detali.ru/cat/oem_mb2.as....701&VIN=*&CT=M&cat=042&SID=07&SGR=013&SGN=01
If so,don't strip this down any further than the parts which are listed as being available separately.The central piston works to tolerances of thousands of a mm & pulling it apart can lead to more problems.

 

[scott2gogo]

Try new fuel, and fuel filter . You may find the old petrol has clogged the metering unit up as it will have gone stale after this period of time.

thanks for suggestion but have done this already, cheers andy

 

[scott2gogo]

First thoughts are that the warm up regulator (part 270 in link below) has failed,causing it to run fully rich all the time.
http://www.detali.ru/cat/oem_mb2.as....701&VIN=*&CT=M&cat=042&SID=07&SGR=070&SGN=02
Should have 12v & an earth on the leccy connection.Easy to strip down.

At the other end of the scale,check the inlet system & all the rubber breather hoses for air leaks.

thanks, will try these ideas at the weekend, cheers andy

 

[scott2gogo]

Does she smoke at all? you can remove the bank of injectors whist still attached to the fuel rail, drivers side is easier than the passenger side and the throttle link needs to be removed as does the solid Y pipe in the valley, some other odds need removing too, worth removing though as the old injectors can leak and if they just push or drip fule through uncontrolled then it sounds and feels like a misfire.

Put a long screw driver on each injector and listen, they should ahave a good click to them and if ones not working well you will hear it.

Be aware new injectors are £282 each and Bosch dont make them anymore, MB only or used for about 60-80 quid each.

Seals can be bought from MB for pence and they do perish, the fuel rail has two regulators one for fuel in and one for fuel out.

Me i'd put £100 on the injectors being duff.... runs good when cold but once warm misfires.

jib

thanks, will try at weekend, cheers andy

 

[scott2gogo]

JIBCL is referring to the old EFI system.By '77 it should be on the CIS system that I referred to.Can you confirm that this is the 'head' that you referred to in your original post.
http://www.detali.ru/cat/oem_mb2.as....701&VIN=*&CT=M&cat=042&SID=07&SGR=013&SGN=01
If so,don't strip this down any further than the parts which are listed as being available separately.The central piston works to tolerances of thousands of a mm & pulling it apart can lead to more problems.

thanks, hav'nt touched the head yet as am very wary, will try other ideas first, cheers andy