200 W124 - Starting Issues

[Fidel]

OK, This is more as an info. thread than a question, just to help anyone else who may have had the same issues.

My trusty 1993 200 always started, until a month back. One cold morning I twisted the key, touched the pedal, and all I got was the starter motor turning, no ignition.
Right, so went and bought plugs ( NGK BCP6ES ), fiddled with vacuum hoses, checked fuel flow, etc. After changing plugs, it started perfectly.
Next day, go and drop wife at the airport, turned off car, helped get her bags out, kissed goodbye, and the car won't start ( warm now ). The guards got suspicious of me not being able to start in a stop 'n go, but after an hour it just started firing and I was able to go.

Since then, I have been looking at everything, and checking everything I could think of ( reading plenty on these forums ), and trying everything out.

My lifestyle and planning had to change dramatically, given that I couldn't go anywhere else within an hour after arriving somewhere. My main fear was stalling in traffic. ( )

I didn't take it to anyone, because I have an unlicensed 230E that I can just risk driving ( would rather not ), and I have just been laid off, and have not secured another job, so every cent counts.

Anyway, today I climbed in and thought to take a look at the plugs I changed at the start of this hassle. I checked plug gaps on the internet (.8 mm ). They were correct.
I looked at the old plugs I had removed. ( Champion S9YC ) and saw that the gaps were way different ;- 1.1 mm.
Now, I don't gap new plugs, because I thought that was the manufacturer's job.

I installed the old plugs, and now my problem appears to be over.

Last thing I would have thought.
I hope this post may help someone in the same bucket one day.

Any ideas on this strange phenomenon ?

 

[grober]

Your problem has probably nothing to do with your spark plugs. Much more likely to involve the ignition switch or ignition immobiliser/alarm working intermittently. Its co-incidence the car ran/didn't run when you changed the plugs. Do a search on the forum for immobiliser/alarm problems. I predict your problem will return sorry.

 

[Fidel]

Grober is, unfortunately, right.

I am finally going to appeal to the wisdom and knowledge of the forum.

My car is a 1993 W124 200 (auto) with a Pierburg 175 CD carb.

The symptoms are as follows :

When cold, the car starts perfectly and instantly. I know to not touch the accelerator before turning the key.
Once warm to operating temperature, if I attempt to start it within 2 minutes, it starts OK, but any longer and the engine turns, but there is absolutely no ignition.
letting the temperature drop by about 20 degrees, to 60 or so, one cylinder starts firing when the pedal is fully pushed to the floor.
As the engine cools down further, the firing becomes better ( maybe a second cylinder kicking in ? ), but not enough to start the engine. When the pedal is not fully depressed, there is no ignition.
When the gauge shows a drop to below 40, ( the lowest temp. shown on the gauge ), I can generally force it to start with foot depressed, and a roar as it catches.
It seems like petrol starvation of some type, but when driving, it is smooth, no power loss or any symptoms, only when starting.
Idling is also perfect.

I don't have an immobiliser fitted.

Thanks in advance.

 

[stwat]

A 93 with a carb?

 

[Fidel]

Stwat, yes.

Locally made in South Africa, so maybe a bit behind the models coming out of Germany.
( Hey, I love the old S class )

 

[stwat]

Moisture in the distributor that could maybe condense in the cap as it warms up? It's certainly worth checking. How old are the leads cap and rotor arm?

 

[grober]

So I take it we are talking about the single cam M102 engine are we? In which case you would maybe have the EZL ignition unit? Your best bet is get it on an old fashioned oscilloscope based engine analyser and look at the ignition firing lines. If its the M102 engine then I don't think you have the correct plugs? You need NGK BP6EF not NGK BCP6ES which are for the twin cam engine.

http://www.ngksparkplugs.com/docs/tech/design_symbols_plugs.pdf

 

[stwat]

do the carb engines have EZL ?

 

[grober]

do the carb engines have EZL ?

May just have the solid state triggering device - this is uncharted territory for me.

 

[219]

A few more ideas -

I wonder if you're getting a vapour lock somewhere in the fuel system ?

As it isn't an injection engine , I guess you won't have the injection type fuel filter under the back of the car - is there a fuel filter in the engine compartment , one of the old fashioned ones where you can see into it ? Is the filter full of fuel , or can you see bubbles in it when the engine is running - a sign of an air leak into the fuel line ? ( Stu - I guess it is going to be similar to a 190 with the carb engine - only I've never came across one ) .

Other thoughts - does the carb engine have an electric fuel pump ?

If yes , there could be a fuel pump relay - those can cause trouble due to 'dry' solder joints on the circuit board inside the relay module , and can be prone to giving trouble when hot after a bit of use - this would fit nicely with your symptoms .

If no , and you have a mechanical fuel pump , it could be a busted diaphragm , again a common enough problem on some of the older cars .

Is the Pierburg 175CD anything like the Stromberg 175 carbs ? They too had a diaphragm which could split and cause problems . I remember Strombergs had a dashpot which had oil in it - lack of oil and it jammed up , that is IIRC : it's been a while

Finally , I wonder if you might have a hairline vacuum leak somewhere on the inlet side which is opening up when hot and closing again as the engine cools - there may be enough suction with the engine already running to keep it going , but just not enough vacuum to get started once you stop . Vacuum leaks are usually down to perished pipe connections for the central locking and all the other vacuum driven things these cars have ( headlamp levellers etc ) .

Incidentally , I've on occasion had similar issues with some of my M103/4 engined cars and found that a change of plugs usually cleared the fault when it arose .

 

[Fidel]

STwat - That's a thought. I changed the rotor on buying the car 3 years back, but left the cap and leads unchanged.
This weekend I am dedicating to finding the issue, and solving it. I have an '89 230E ( injection ). I'm wondering if the cap is the same, just to see if it makes a difference.

Grober - I'm just waiting for it to get light outside, so I can take a look and see if it's the M102. I'm running on the Champions now ( S9YC ), which according to the internets are correct.

STWat & Grober - EZL? What is the image of, and where do I find that thing under the bonnet?

Pontoneer - There is a mechanical pump on the engine head, with a fuel filter attached to the carb body. ( 2 weeks old ). The filter is never full, but the inlet / outlet to it is covered in petrol. I am familiar with the big filter at the rear on my 230E ( recent electrical fuel pump change ), and I don't think this one has the same.

The carb has a damper with ATF in it. On the day I couldn't get it started cold, I made sure that it was full of ATF. That was the day before my warm start issues came up, so this last weekend I took a little out to try and revert back to everything being the same as before.

I have now been examining all the vacuum hoses and connections, and actually found 2 leaks and replaced the parts. That seems to make no difference. The vacuum situation on this car is horrifying :- there are vacuum hoses going everywhere, and try as I might I can't seem to locate a vacuum diagram for this car.

Guys, thanks for the replies and ideas. Based on your input, I now have a plan of action :

Clean out cap, maybe put moisture repellent in.
Swop out cap with 230E ( if it's the same ).
Disconnect petrol feed from fuel pump, and see if fuel comes out when trying to start warm. ( I want to check first - I'm nervous of breaking a perfectly good diaphragm ).
If not, open it up.
Check carb diaphragm.

I hope I can sort this.

 

[grober]

THERES ALINK TO A CARB MANUAL HERE http://www.mbclub.co.uk/forums/engine/26469-stromberg-175cd-carb-manual-required.html
HERE'S A PICCY OF AN EZL

 

[Fidel]

Greame,

Yes !! I found my EZL - I have no idea what it does ( seems to be something to do with ignition advance ).
Mine is a bit simpler than the photo above, but it says '4zyl' and is made by Siemens.
Can this stop starting when it's warm?

PS. Thanks for the Pierberg diagram. I see that there is a temperature compensator listed, so I tried to find it on the drawing, but the numbers don't seem to add up.

 

[Ardveen1]

Hi, picked up a non starter W124 E220 coupe, 1994 model, lots of history with 118k on clock ( genuine ), car has only covered 30k since 2006 with only 5k in last 3 years. body in great shape, only small paint bubble beside aerial. Car was non starter, nothing when key turned, not even a click, so had to tow it home with my ML 270 and lidl steel tow bar, towing auto's ok per manual at slow speed in Neutral. Owner reckoned starter motor was the issue, lots of strange elextrics going on, when battery connected alarm hazards on immediately, cycling on / off then until battery drained, paid small money so decided i would invest some time as car really in great nick for its age,
First I decided ( with the advice of the forum ) to remove the scorpion alarm. The siron was already disconnected. When poking and found the control box cable tied below steering column, panel below column has to be removed, also removed floor carpets and side panel in drivers footwell. I removed the scorpion control box and traced the wires. This unit cuts out the fuel pump and starter motor. The fuel pump bypass was located in the plastic cable tray at the side of the drivers door, I cut these alarm wires and reconnected the fuel pump wires together to restore direct feed to pump. I also cut out the alarm wires feeding the door and boot sensors, internal movement detector and red dashboard light, then traced the wires into the engine, they enter from the car into the box below the main fuse compartment, this has to be unscrewed for access, plenty of slack to pull fuse panel to the side and allow access. They were a few alarm wires spliced onto other original car wires which I cut out. The fuel pump and siron feed leave the side of this fuse board underbox and head over to the battery side behind the firewall, on the battery side I found the starter motor cut out and reconnected the wires together and stripped the remanants of the alarm out. I fired the car and voila, the starter motor turned the engine, started for a few minutes roughly then cut out, it would not start again.
I thought fuel pump and decided to change filter, Still no go so I ran a direct feed to the pump and it worked, then loosened the fuel rail bolt on the engine and got fuel coming out. This car has the M111960 engine with coils to the side, not easy to get at but wiring harness looked ok, no oil residue in expansion tank so no head gasket issue either.
I then investigated the relays behind the battery, removed the green fuel relay and bypassed outer terminals by linking with copper wire, ( fuel pump ran continuously ), still no start though. Remove the OVP relay and also the kickdown one. I bench tested the OVP as per google instructions and it was leaking current. Bought a replacement OVP on ebay ( nearly new £35 ) and also picked up a spare kickdown in case there was an issue here also ( £7 ). I put both items in and hit the ignition.
It fired up and has been running ( very sweetly ) since.
The forum was a great help in my investigations so I thought it fair to share my experience, it may help someone else.

 

[grober]

Excellent example of what may be required to put an old Mercedes with alarm problems reliably back on the road. A warning for all who think its merely changing a fuse or joining a couple of wires back up. My only comment for anyone doing this would be to handle the existing MB wiring loom with kid gloves especially anything in the engine compartment as a 94 car is in the dodgy wiring insulation "window" .

 

[optimusprime]

Your problem has probably nothing to do with your spark plugs. Much more likely to involve the ignition switch or ignition immobiliser/alarm working intermittently. Its co-incidence the car ran/didn't run when you changed the plugs. Do a search on the forum for immobiliser/alarm problems. I predict your problem will return sorry.

Grober do you remember mine [immobiliser] fault.