W124 300CE 24 non runner

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Dimitris1969

New Member
Joined
Nov 7, 2023
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18
Location
London
Car
W124
Hello Club

I have a W124 300CE 24 for almost a year and for the last 11 months is sitting in a specialist garage who is trying to find why the car dose not start.

I have changed the ECU, the fuel pump, the fuel pump relay, and a numerus other items but still the car does not want to start. They have measured the engine compression, replaced spark plugs check the distributor and run a diagnostics on the car.

In my previous life I was a car mechanic but now I have decided not to deal with such problems as I have no free time, young family and two jobs.

As being a car mechanic, some 20 years ago, and now being a mechanical engineer, I believe that no problem is unsolved specially when it comes on older cars which are simpler to fix.

I believe that the issue is with the alarm that is not working, causing some electrical problem. The mechanic ensured me that there is no electrical fault and there is fuel in the fuel injection pump.

Now, does anyone know a garage that is competent and can solve this problem of the non starting W124 300CE 24.
 
IGNITION SWITCH,OVP RELAY, EZL IGNITION UNIT??? CHECK THE IGNITION UNIT IS GETTING AN ENGINE SPEED SIGNAL FROM THE FLYWHEEL OR DASH ELECTRONICS
 
I will ask what is been replaced and all works that they have done and come back with a more comprehensive response.
 
Suspect the ignition module (EZL) but that’s just my guess 😊 was a common issue on these engines and expensive to replace.

In reality though, who worked on it? What’s the issue - ignition or fuel? I can’t see it being both.

If it’s got compression, is getting fuel and a spark it will fire.

Did the car run okay when you got it? Only reason I ask is that you say you’ve had it a year but it’s been at the garage for 11 months (?)

Where abouts in London are you?
 
I am not sure if that’s been replaced.

I have bought the car more than a year ago and it was running fine, difficult to start and running a bit high on idle but it was running.

After one month of use, one morning, it refuse to start. I tried to see if there is fuel in the injectors and also checked the distribution and cables and all were fine.

I did manage to start it once but it was running very rough.

As I had no time to deal with it, no ramp to lift it and no dry place to work I decided to send it to a local specialist , highly rated , to fix it.

They check compression , I don’t know why, spark, I bought an ECU and a MAS relay and the two fuel pumps which were replaced by the garage.

I told the mechanic that if they get a spark and fuel then they should have ignition but I go no response from them.

They are waiting for a donor car to come in, a CE300 24V and try to trouble shoot it.

Any help will be appreciated as I would like to use the car on a daily basis as it is suppose to be used.
 
A second hand ignission module will cost around £100. Can this be checked and if not shall I just get one and try it up?
 
Who is the specialist that has been puzzling over your car for 11 months?
 
Will it run on easy start? Not keen on the stuff but if it runs then sparks are there.
 
A second hand ignission module will cost around £100.

Sadly, that's not true. If this is a 300-24, assume 350+ for used. A couple of years ago they were available new (NOS) for 1200€. Don't know now. My usual geuine MB supplier still lists the EZL:

1699446429354.png

The compatible (assuming it's a Euro car, not US California, etc.) EZLs are:
A0125452032 (Bosch 0227400738 - backwards compat.) or: A0125452132 (Siemens EZ0051 5WK6 K30575HR1 - backwards compat.)
Original probably: A0105459532 (Bosch: 0027 400 736) or: A0105459632 (Siemens equivalent)

Have you got a spark? If so, I'll bet the EZL is OK. And the Crank Position Sensor should be OK too.

The HT system needs to be 100%.

Your garage seems to be lost. Find a specialist.

In your shoes, I'd start with the HT system. Coil to plugs, ideally MB original. Costly? Yes. Justified if you're serious about the car.

As others have said, you need to start with some diagnostics. Is there a spark? Does a squirt of starting fluid fire it up, even if briefly?

If you have spark and an occasional fire, maybe filters are blocked.

Did you try a known good MAS box? That starts to fuel pumps and you'll get nowhere without the pumps running.

I'm rambling a bit but I hope you get the picture.

Good hunting.

RayH
By the way, I'm not an expert, just someone who's had a 300-24 for over a quarter of a century. Mostly reliable but I did lose 3 EZLs in 9 months due, we think, to a faulty coil.
 
Will it run on easy start? Not keen on the stuff but if it runs then sparks are there.
Yes, thats the first thing that I tried. No change. Thats why I think this is an electrical fault.
Also the car has an old cobra alarm that is not conncted on the module. It was like that when I got it and it was working OK. Im not sure if the old alarm can cause the car to not start and I did not want to tamper with it.
 
Sadly, that's not true. If this is a 300-24, assume 350+ for used. A couple of years ago they were available new (NOS) for 1200€. Don't know now. My usual geuine MB supplier still lists the EZL:

View attachment 149189

The compatible (assuming it's a Euro car, not US California, etc.) EZLs are:
A0125452032 (Bosch 0227400738 - backwards compat.) or: A0125452132 (Siemens EZ0051 5WK6 K30575HR1 - backwards compat.)
Original probably: A0105459532 (Bosch: 0027 400 736) or: A0105459632 (Siemens equivalent)

Have you got a spark? If so, I'll bet the EZL is OK. And the Crank Position Sensor should be OK too.

The HT system needs to be 100%.

Your garage seems to be lost. Find a specialist.

In your shoes, I'd start with the HT system. Coil to plugs, ideally MB original. Costly? Yes. Justified if you're serious about the car.

As others have said, you need to start with some diagnostics. Is there a spark? Does a squirt of starting fluid fire it up, even if briefly?

If you have spark and an occasional fire, maybe filters are blocked.

Did you try a known good MAS box? That starts to fuel pumps and you'll get nowhere without the pumps running.

I'm rambling a bit but I hope you get the picture.

Good hunting.

RayH
By the way, I'm not an expert, just someone who's had a 300-24 for over a quarter of a century. Mostly reliable but I did lose 3 EZLs in 9 months due, we think, to a faulty coil.
Hello Ray

These guys are a MB specialists, that’s what they fix, only MB…but they can not fix it and that’s why I am trying to find another specialist that can fix it.
They have stated that they run diagnostics, that there is a spark (i also checked it and I get spark in 2 cylinders) the fuel comes out from the pump connector on the fuel injection distribution module and form the fuel injector nuts, the fuel injectors have been check recently and they are OK, the fuel pumps and filter are new (have been replaced) and the prime when you turn on the key.
I don’t believe this is a fuel issue.
 
Let us know if & when it becomes professional.

TIA.
 
They have stated that they run diagnostics, that there is a spark

Glad to hear that. Your EZL seems to be working. I'm happy to share my thoghts on preserving EZLs, when you get this sorted.

I still have my doubts about their competence. Maybe they don't understand these older cars.

Bonne chance.

R
 
Glad to hear that. Your EZL seems to be working. I'm happy to share my thoghts on preserving EZLs, when you get this sorted.

I still have my doubts about their competence. Maybe they don't understand these older cars.

Bonne chance.
they dont,
I still after 11 months have no car and alternative garage to fix it
 
I'm happy to share my thoghts on preserving EZLs, when you get this sorted.
I was told 2 things kill EZLs, heat & damp. Replacing the O rings & slathering the base with heat sink may prevent premature failure on these increasingly hard to find units.

That's leaving aside outside influences like dodgy coils.
 

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