hello all...
I am in desperate need for help!! I own a merc 300se 1990. In the last year i started having trouble with the engine! It starts nicely when cold! but after it warms up engine cuts out and is v.difficult to start again without foot on the peddle. I have replaced the idle adjuster,plugs,plug leads,coil,co2 adjustments,cleaned distributor,cleaned injectors,but the problem remains!! I like to try and fit a new oxygen sensor!maybe it will solve my problems,but i can't find it!! I am not sure if my car is fitted with a catalic converter or not.I have looked under the car and found three barrels but nothing attached to them! then i tried finding it on the manufold,but still couldn't find it.If anyone understands what i mean PLEASE HELP!!!

On my 124 (a US car) it is on top of the exaust pipe just engineward of the cat.

Do you have a cat...
Starting from the tail end of the exaust there are two mufflers followed by the cat then on to the exaust manifold...

It is often covered by a clip on shield and there is a wire from it into the front seat tunnel wall...

good luck.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

thanks for that Marty! i'm sure now my car is not fitted with a converter cause the last muffler before the manifold is a very small one,and there are no attachments to it! i have looked under the front passenger's carpet,but without success.I know from photos how it should look like!,and in this case it should be somewhere on the manifold. i know this might sound stupid, but i can't bloody see it.Cheers

I don't think the oxygen sensor has any influence on starting. The control system ignores the oxygen system until it gets to operating temperature.

Check fuel pressure during hot restart. Most likely something isn't providing enough fuel under that condition. Maybe a tired accumulator or check valve?

An alternative to cranking for long periods is to crank in a short burst, count to 3, crank in a short burst, count to 3... I expect the engine will catch by the second or third try. Common M103 malady. There is an answer but I never found it. Part of the reason I got tired of my 91 300SE.

Sixto
... stay tuned

hi sixto..
ty for that.The problem starts at operating temp.engine surges,and after a couple of minutes cuts out stopping at trafic lights etc....it would not start again unless foot is on accelerator.once foot is off engine would cut out again and dies.I have spent over £1000 on new parts and labour in the last year,but reached nowhere! i feel now that most garages,including the mercedes dealership in my area are all guessing!thats why i'm gonna try myself even though i dont know much about the whole thing.I dont want to throw money away,and at the same time i want to keep this car cause it is v.dear to me
best regards

http://www.peachparts.com/Wikka/EngineControls

Sixto
... stay tuned

read everything at the authors site as well. great reading. thank you.

Jason

__________________
1988 300CE 120K RIP(Midnight Blue/Parchment)
1987 300E 202K (Arctic White/Palomino)


Now I see the secret of the making of the best persons. It is to grow in the open air and to eat and sleep with the earth. ~Song of The Open Road

Last time i took my car to the dealership was two months ago,and i swore never to return.this morning i had a call from them asking about the car,and how it was doing!after a long discussion they offered a free check on monday morning and promised to find out what is wrong with it..i will give them another chance and will tell you all about it.maybe it will help someone with the same problem.cheers