'94 E200 intermittent start problem

[wasda]

Hello,

I am new and I am having a really heartbreaking problem with intermittent warm starts on a ?94 E200. I go out somewhere and once I park, go away from the car and come back, it will not start.

I have had it in several garages. Last week I had the crankshaft sensor replaced and this fixed the problem for a few days (or so it seemed) but today the problem returned and left me stranded again for several hours. It has a new battery and tries to start but just will not spark.

I have a few questions and any help would really be appreciated as this has caused a lot of trouble and heartache already

1.The car had the thermostat removed about a year and a half ago, could this cause an incorrect reading in one of the sensors?
2.I have read quite a bit on the forum about the OVP, could this be the cause?
3. Where is the OVP on an E200 so I can check the fuse?

I am basing my questions on what I have learned from reading a lot on the forums in the last 6 hours plus any little information I have garnered from mechanics over the last 2 months.

This problem has been going on for over 2 months now so any help anyone can offer would be greatly appreciated as I am at my wits end.

Thank you in advance for any assistance.

 

[Doinitmyself]

The OVP relay is behind a plastic cover behind the battery. It has a plastic flip up cover with a fuse under it. Don't get your hopes up the fuse will be fine! The OVP relays can cause starting problems but generally only when cold. Probably worth a try by now though! Is it a 16 valve engine?

 

[Mikesmerc]

Had a similar problem on my 124 230e a few years back. I found the culprit by wiggling a few wires around the engine bay and turning the ignition each time. It turned out that it was a faulty EZL unit(ignition module) mounted on the inner wing, 4"x4" flatish black plastic thingy with a round plug. Replaced it with a new one and hasnt failed to start since. Worth giving the plug a wiggle next time it fails to start.

Rgds
Mike

 

[Stevie A]

I am having a non starting problem which I am hoping to solve tomorrow. If your car has a similar engine to a 190E then there are various sensors that could cause your fault.
1. Coolant Temperature Sensor
2. Crankshaft Speed sensor
3. Inlet air temperature sensor
4. TDC Sensor

Seems to be temperature related so I would try replacing the coolant temperature sensor first. All of these send info to the ignition control unit and if any are sending wrong readings or no readings then you can have problems. Check if there is a spark when it won't start - if there is a spark then it could be the fuel pump relay or OVP relay that is defective. But try the coolant temp sensor first, I don't think they are expensive but don't know for sure. A haynes manual shows how to replace it. It is a simple job. Haynes manual shows correct resistance for temp sensor too:
should be:
6000 ohms at 0 degrees C
1200 ohms at 40 degrees C
325 ohms at 80 degrees C (when fully warmed up)
Measure with meter across pins in X formation if it is a four pin plug.

 

[wasda]

Thank you very much for the replies,

I had a new fuel pump relay put in and it went ok for a few days. The problem has now returned with a vengence. It has now taken to cutting out in traffic as well. There does not seem to be a pattern to it, just stops whenever it feels like it.

Here is all the new info since I last posted.

1.There is no definitley no spark when the start problem occurs, does this rule out the OVP relay?
2.I now have a new crankshaft sensor and fuel pump relay.
3.The fuse on the OVP relay is ok
4.The cutting out is a new twist in the plot.

Stevie A, thank you for the info, I am sorry to ask such a basic question but where is the temp sensor? I have a multi-meter and I would like to test the ohms as you suggested.

I did a web search for Haynes, I found their website but none of their currently available manuals seem to cover my model. There is one for E-class from '95 onwards but it may not be of use and is not available at the moment anyway.

I am also unfamiliar with the TDC sensor, if it not too much to ask could you please tell me what it does and if there is a way of checking it.

I really appreciate everyone who has taken the time to answer my post. I am sorry I did not reply sooner but I had a few computer problems as well (it never rains but it pours!)

Thank you again and I will post the solution once the problem is fixed so that this thread might be of some use to someone else suffering from a similar problem

 

[mike65]

The temp sensor is at the front of the cylinder head

I had a faulty one but its did'nt cause the symptoms your car displays (my issue was hard starting when warm but it always did start after a number of cranks).

Mike.

 

[wasda]

Mike, there is some similarity as warm starts are the big part of the problem.

I have been out in the dark with a flashlamp trying to find the sensor as indicated in your photo. I have not had any luck. Perhaps I am looking in the wrong place. I took a couple of photos of my engine from a wider view to use for reference. They are a bit shaky because I took them in the dark. I am just compressing them now and I will upload in a few minutes

 

[wasda]

Here are the wider shots of the engine and have the areas I was looking in marked in white. In the second one, I looked under the cover at the front as well.

 

[Stevie A]

I don't know for sure where the coolant temperature sensor on your car is as I don't know the engine. Is an E200 a 2 litre engine the same as the 2 litre 190E? Experts please help?

Just because the OVP relay fuse is ok doesn't mean the OVP relay itself will be ok. Find the coolant temp sensor first though.

Also - Was the thermostat changed? Or just removed? If the thermostat was removed and not replaced then the engine would run colder than normal. What temperature is on your temp gauge when it is warmed up? It should run about 80 degrees when warmed up. If it's running colder than that they maybe someone could have taken the thermostat out if they were having warm start problems???

If there is no sparking from the king HT lead from the coil to the distributor when the car refuses to start then that points to an ignition system fault eg sensors / ignition control unit / ignition coil. If there is a spark on the HT king lead then the distributor could be at fault. However, your problem seems to temperature related so check the temp sensor first.

I read a thread about fuel pressure and temperature affecting the running, particularly when the car is warm - there is a thing in the fuel pump that keeps the pressure high enough, if that is failing then your car would stall and be harder to start. No sparks = igniton fault. No fuel = fuel side fault =fuel pump / fuel pump relay. I think both sides are affected by the OVP relay.

Don't change stuff though for the sake of it and waste money. Take it to a specialist or dealer garage and get them to run it til it shows the symptons and they will know what the problem is.

 

[mike65]

Those pix are terrible! You know that engine looks somewhat different even though it should be the same one if its a 2 litre (102 engine)

The location of my picture is just to the right of the oil cap, theres are several sensors packed in at that spot.

I read a thread about fuel pressure and temperature affecting the running, particularly when the car is warm - there is a thing in the fuel pump that keeps the pressure high enough

Thats the fuel pressure regulator. Does the car stall with a splutter or just die quietly? Is the fuel economy poor, can you smell unburnt fuel?

Vapor lock is another possibility.

Mike.

 

[wasda]

Stevie, There was an issue with the thermostat before. I am not sure if it was replaced. The car runs at about 80 , goes lower on the open road and higher when sitting in traffic.



Mike,Those photos have the official shaky hand middle of the night look. :grin: I have done a little more research. The engine is a W124 as far as I know, so that would explain the different layout. When cutting out, the car just dies quietly,no spluttering.

 

[wasda]

I have checked with several garages and none of them have an OBD plug that will fit on my car. The 3 existing standards were introduced in 1996. I know a man with an excellent background in electric and electronics who can make a connector to fit but I really need the wiring diagram for the OBD connector on the car. Any help would be greatly appreciated.

'94 E200 (W124)

 

[mike65]

The body is a w124 (Merc chassis numbering system) the engine numbers are 102 (2.0/2.3 ltr) 103 (2.6 ltr).

There is no definitley no spark when the start problem occurs

I think this is the thing to concentrate on, you could have more than one cause of your problems but I'd say its all down to the sparking (or not!).

As the other Mike said, I wonder if you have a shot ignition module?

Mike.

 

[Myros]

If it is the OVP

the fuse will be fine, it's the soldered joints in the relay itself which are suspect. Had similar trouble with my C280 last year, and the fuse looked wonderful.

 

[wasda]

Mike, thank you for that and sorry for my error. I am only learning as I go. After further research it seems that the engine is the 1998cc "M111" fuel-injected 16 valve 4 cylinder.

Myros, thank you, is there any way to check the OVP relay without a diagnostic?

 

[mike65]

Ahh! The M111 is a completly different kettle of fish - bosch Motronic system. It replaced the 102 engine.

Mike.

 

[wasda]

Sorry about that Mike, I am on a very steep learning curve here at the moment.

 

[wasda]

Also - Was the thermostat changed? Or just removed? If the thermostat was removed and not replaced then the engine would run colder than normal. What temperature is on your temp gauge when it is warmed up? It should run about 80 degrees when warmed up. If it's running colder than that they maybe someone could have taken the thermostat out if they were having warm start problems???

Stevie, I checked on that and there is currently no thermostat in the car. Could this be a part of the problem?

 

[Myros]

not too sure about the ovp diagnostic

as it would have to be misbehaving exactly when the test was run. If you go on an escalating scale of costs for parts replacement, it's probably at the cheaper end of the scale at approx £50. Try mercman or similar and see if they have a known to be good used one for much less.

 

[george shand]

Ovp Relay.

Available from Europarts, £38.00 + VAT, not stock item ,part no. from old unit required when ordering.
Similar stalling problems on my 1995 C220, have OVP relay on order ,will post result when fitted Mon or Tues.