Ignition Problem

spacemoc

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Hi all,
I have 300 se 1987 and from time to time when I am trying to start it, it doesnt work, whole care is shaking until I add some more pressure on the gas pedal then its stops and running okay.

Or you need to keep key turned right for at least 5 - 10 seconds to start it.

Anyone know what could be the problem ?

Seb
 

television

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Condensation from the sump is the biggest problem and this rises into the dizzy cap, try wiping some PTFE around the inner surface and also the rotor arm including the under side
 
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spacemoc

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Ignition

I have changes dizzy cap and rotor for brand new original Merc part and still got the same problem (maybe 15 % improvements), car ignition is very problematic. Do you think so this may be related to oil pressure or maybe the oil filter is not genuine and needs replacement? pictures below old cap and rotor vs new ones

1.jpg

2.jpg
 
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spacemoc

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w126 300 se starting problem

there is a similar post on this forum http://forums.mercedesclub.org.uk/showthread.php?t=44488
this is exactly the same behavior my w126 is getting.

anyone know how the problem was solved and what was the issue with the starting problem?

In my w126 doesn't matter if the engine is cold or hot I need to turn key at least 3 - 5 times and keep it turned for 10 - 15 seconds to make it start. Then sometimes the whole car is shaking after start. Then its drive nice and smooth no problems....
 
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spacemoc

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It must be a solution here for this annoying problem...
 

wireman

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It may be fuel related.

It will definatly not be oil pressure related, there is next to no pressure when the engine begins cranking, anyway without oil it will start perfectly and then eventualy expire in a spectacular or at least noisy fashion...

Are the HT leads in good order, don't fit solid wire ones use the proper type if you replace them since the ignition systems components were designed to use suppresion cable it works best with them.

The rotor arm and cap pitting on your pic is quite normal, using solid wire leads makes for much deeper pitting and eventual failiure, some rotor arms have a burried resistor for suppression in their mouldings, these should measure around 2K to 20k ohms.

Are the spark plugs up to snuff?

I cannot determine from the pics as to what fueling system is in use, carb or injection.
If its injection there is a startup valve/injector on some installations (D&K jetronic) which may be defective. This fault would have no effect on normal running once it is running.

If its a carb an air leak or damaged diaphragm in a variable jet carb may be at fault.

On some carb models an air admission valve is fitted to the manifold to open it up to air when the ignition is switched off preventing the engine from running on or "diesling", if its dodgy expect poor startup and possibly bad overall running.

The spark plug electrodes should be a nice pale chocolate colour, if they are white (to weak) or black (too rich) this should suggest carb/injection trouble.

Are the vacuum operated acessories (lamp adjust heater etc) working? if not an air leak is possible from these systems.

On a carb the fuel pump valves can have the effects you mention.

On an injection system a deficiency of the fuel pump relay might cause this, the relay will hold in when running but is engaged by the starter being operated, if the starter connection is lost the fault is as you have.
 
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spacemoc

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thank you, do you know any good garage or anyone who know w126 very well so I can go and fix it as its so annoying, Heating is no problem.

Seb
 
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spacemoc

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Fuel Filter

Or it could be a Fuel Filter ?
 


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