W124 E200, no power to fuel pump

[Brightjae]

Hi guys, my w124 E200 (m111.940) recently broke down, it suddenly stopped on the road as if I had run out of gas, it started up again after at least 10 tries. I took the opportunity to bring it home but since then it won't start at all! I noticed afterwards that the fuel pump no longer made a sound when I turned the key. So I first changed the fuel pump with a new one (it had trouble accelerating at high speed and climbing hills on the highway so for me it was logical that it was the fuel pump that was starting to fail ) but still impossible to start.. I exchanged the fuel pump relay with my brother’s relay (w124 E220, it's the same relay) his car started, not mine.. so it's not the fuel pump relay. And I can hear the *click click* of the relay. I recently changed the OVP to an original one but no change. I saw on other forums that you can force the fuel pump by connecting pin 87 and pin 10 of the fuel pump relay but on mine I don't have pin 10 (I would try to put a photo) I'm starting to have no solution, if someone can enlighten me.. thank you in advance
-Pierre

 

[Brightjae]

Update: I just realized on looking more closely that there is a cut wire that goes from the small green relay to the left of the ecu (photo below) there was tape at the end of the two wires, on the relay side the two wires are twisted together, and on the ecu side it's a clean cut, it's strange. Someone know what it's for??, could that be the problem?

 

[grober]

Probably a remnant of an aftermarket alarm system which has been disconnected/removed and the original connection restored.The other relay thats often disabled by an alarm system is the OVP RELAY- might be worth checking that?

 

[optimusprime]

Not a Mercedes plug .

 

[carrington]

so if the relays good are you getting 12v at the pump?

 

[DSM10000]

The other relay thats often disabled by an alarm system is the OVP RELAY- might be worth checking that?

The OP mentioned that they had already changed the OVP relay.

 

[Brightjae]

Thank you for your answers, to be honest I am new to electronics, and I do not know where to start. I had a multimeter but I lost it, I will buy one and do some tests, but I don’t think I’m getting 12v at the fuel pump. I also did some research on the green relay in the photo and apparently it’s also a relay for the fuel pump, and the cut wire is connected to this relay.. so it’s connected to nothing.. Anyone know who is supposed to be connected this green relay?

 

[DSM10000]

Thank you for your answers, to be honest I am new to electronics, and I do not know where to start. I had a multimeter but I lost it, I will buy one and do some tests, but I don’t think I’m getting 12v at the fuel pump. I also did some research on the green relay in the photo and apparently it’s also a relay for the fuel pump, and the cut wire is connected to this relay.. so it’s connected to nothing.. Anyone know who is supposed to be connected this green relay?

As said by Grober that may have been some wiring to an alarm.

Ideally you need to get yourself a wiring diagram for the vehicle.

Can you supply 12v directly to the fuel pump and see if the car starts?

 

[optimusprime]

Dsm10000 Yes i saw that ,,but so many swapping parts out , and put another part back in just because it looks the same .You and i know , that if a specific part is removed , then the exact same part with matching part number must be fitted . I had a problem few years ago . After getting my car out for the first time after the winter . And it would not start . I did everything i knew, and i tried all the old parts that i had removed that i had kept over the years just in case this cropped up . And i could not get the engine to start . In the end i gave up called in an auto technician .Problem was failed alarm .He took off 4 wires to get it running .Then bit by bit i removed the rest of it .

 

[DSM10000]

A 12V feed direct to the fuel pump is the next test.

This will prove that the pump is operational or not. If it is then the wiring can be traced back to find the fault that is preventing it operating normally.

 

[Brightjae]

Yes you're right, that's the next thing I'm going to do, I'm going to put 12V directly on the fuel pump, I'm just waiting for the rain to stop, I'll let you guys know

 

[carrington]

what year is the car, that green cube doesn't look anything like the fuel pump relay on my old 230...

 

[optimusprime]

Poster is holding his fpr in his hand .

 

[carrington]

D'Oh

 

[neilrr]

PMS unit?

Check for spark on ignition at the end of each plug lead.

 

[Brightjae]

So.. I connected the fuel pump with 12V, it works I can hear the *bzzzz* of the fuel pump continuously, but still impossible to start the car. I have already tried another PMS that I had at home just in case. I know it works so it's not the PMS unit. if it doesn't start even with the fuel pump on, it's something else, probably electronic.. my engine harness seems correct to me… What I should do next?

 

[grober]

As previously asked- are you getting a spark at the plugs? You might have faulty crank position sensor.

 

[Brightjae]

I guess yes, otherwise I would have already had error messages like: "no spark at ignition 1/4 2/3" but in this case I have 0 error messages, for the car everything is fine

 

[optimusprime]

So where do you find these error messages from ?

 

[Brightjae]

I use this device