W124 260E: A pig to start!

[belugablack]

I've just bought a 1991 260E to tidy up for my father, all original and FSH. My principal gripe is that from cold it takes forever and a day to start, eventually wearing the battery down after 5 minutes of labouring on the starter, stuttering... when eventually successful in getting it started, it then starts OK for the rest of the day - only to play up again come the morning.

I read with interest the 300 TE comments on gone off fuel and a damp dizzy cap, but I had a 1992 300 CE a few years back that was just as reluctant to start - - spent a fortune at an auto-electricians on heavy duty battery, spark plugs, leads, dizzy cap and rotor, fuel injector clean etc etc and this still didn't cure it - it was always a pig to start. Then a W126 300 SE I owned subsequently would do the same if left unused for a couple of days - - so I would love to know what is up with these Mercs?! They were all cherished, FSH cars, so not neglected old smokers and cars which have never wanted for anything mechanically...

An MB technician has pointed me towards the ignition module, but again this could be a stab in the dark... and at stupid money brand new and still £200 used from a specialists breakers I am loathe to go down this route on a whim for car that I purchased for peanuts, plus there are all manner of different part numbers for these modules, and the only exact one I can find is in Germany and could be as duff as mine!

Does anyone have any experience with these ignition modules please, what is the likelihood that this is the culprit? There's no misfiring once the car has started and it drives smoothly so my limited knowledge suggests a new dizzy cap and rotor might be a waste of money???

Any opinions gratefully received - - at this rate I just may drive it (or tow it!) to the scrapyard such were my stress levels this morning.

 

[Sp!ke]

I suggest it might be prudent to check your cold start valve.

 

[Dieselman]

Ditto.

Or air leak into the manifold, but no1 hit would be the valve or control sensor.

 

[MBManInKen]

Then a W126 300 SE I owned subsequently would do the same if left unused for a couple of days - - so I would love to know what is up with these Mercs?!

I had a W126 300SE for many years and it never failed to start as soon as the key was turned. Never, ever had any starting problems with it, summer or winter, wet or dry.

Not much help, I know, but wanting to keep the reputation of the Mercs intact .

 

[Dieselman]

Try pouring a small amount of fuel down the intake when cranking from cold. That will indicate whether it's fuel or spark related.

You can buy a really cheap flash tester, I've posted the link several times recently so please do a search.

 

[MangoMan]

Also it could be that fuse in that little box (10amp), (red), I think. It's the Over charge thingy, or something. I used to have the same prob on my 300te. replaced it, sorted, so I would presume it was that. ITEM 122 in Diagram...

Ciao.

 

[grober]

I have a vague memory that its part of the fuel pump relay innards that supplies the cold start valve but it might be the the OVP as Mangoman said in which case changing it might solve the problem? You could try removing the cold start valve and testing it for spraying when the engine is cold to check its operation- have something to catch the petrol in!!

 

[belugablack]

Thank you for all the pointers - very grateful. I shall get the car into the autoelectrician next week armed with your information and fingers crossed I'll get the result I am hoping for -- thus far the ideas seem cheaper and easier than sourcing a new ignition module anyway! Then it's on to sorting why the ABS light is staying on...

 

[belugablack]

I thought I'd try the OVP fuse myself, only I cannot find it having searched properly (!), on my SEC it's clear to see in the centre between the front/windscreen bulkhead and engine bulkhead in a red case with a clear perspex lid, on my W124 this area is all cowled in around the windscreen wiper hub... is it really that inaccessable that I've got to prise all that plastic up to get to it because it doesn't want to budge?

Whilst ferretting about I noticed that the petrol grade gizmo was set to "S" for premium fuel, so I switched this to "N" for standard 91RON fuel - - will this maybe help with starting and general running given that I am not putting posh petrol in this cheap car!?

 

[Dieselman]

I doubt it, that just knocks the ignition timing back to stop pinking.