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Discussion Starter #1
Hello

Car: MB C-class w203 cdi
Engine: OM611.962

The engine has been hard to start a long time, now it does not start at all.

What is checked:
Checked with iCarsoft CR plus - no codes.
Battery - OK

Pump relay in back SAM is checked - OK.
Pump fuse in back SAM does not exist (F4). Very strange.... Tried to put a fuse in, but no change.
Could it be that the relay and fuse are not in use? Or remodeled?

Pump in the tank not running.

Pump on passenger side partnr: A2034700794
Sender unit on driver side: A2034700141
Looks like all electrical connections are via "Sender unit". There are 4 wires in the sender unit wire, but in the sender unit there are only the 2 in the middle that have pins, and there are very thin wires connected to these, so dont think it is for the pump....
Is there any other connections for the pump?


Whats next to check?
  • Camshaft sensor
  • Crankshaft sensor.
  • Diesel leakage.
 

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W219 320CDI -07 W220 320CDI -01 W210 270CDI -01 EX: W211 320CDI -04
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What model year is your car? Usually W203 has no pump in tank. What is your VIN, WDX203XX6.. or WDX203XX8... first have no pump, latter does.

Normal symptoms for fuel leak, either in o-rings of low pressure lines, or excessive injector tank leak.
 

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Discussion Starter #3
Model year:2002
VIN: WDB203204XXX66XX6

This means no pump? Even no low pressure pump.

The engine is a bit wet, so there could be a leakeage, been like this for a long time. But it is impossible to see where it comes from...
 

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Low pressure pump is front of the engine. Search OM611 fuel system for schematics.

Can you diagnose system see rail pressure during cranking? If so, its should be arouond 200-250 bar, and fault is somewhere else than fuel starvation.

Low pressure lines are underpressurized, and they usually draws air in rather than leak out (they can leak too). HP pump in front of the car is known to leak between pump piston head. See if there are air bubbles in clear fuel lines (lines may be covered by plastic cover line) when cranking.

Do a injector leak back test

To find out if you are getting fuel from tank (IS there fuel in tank? Should be more than 1/2 tank or when you opened sender units, driver side should have some) you can unplug aux pump line going to hp pump, ask youf friend to crank. If fuel starts pouring out, just hit the line back to pump. It's not strong flow and cannot create high pressure but cover your face/eyes.
 

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Discussion Starter #5 (Edited)
Thank you.

I can not see rail pressure with my diagnistic equipment.
Is is possible to measure this directly on the sensor with a multimeter?
Is there any connection for pressure meter? I can't see any "tire valve" connection...

I unplugged the line from aux pump to hp pump, the fuel is pouring out after a couple of second.
And of course I broke one of the sides of the connector to the low pressure pump, old plastic..........
If someone know the partnumber for this I would be habby.

There is also a part connected to the line between the pumps.
Partnr: a6110780349. Vacuum solenoid valve? What is the function for this?

After connecting, I saw many air bubbles in this line(between the pumps). Also checked lines from fuel filter(near filter), many bubbles also come here.

Maybe I should have checked for air bubbles before I disconnected the line.

After cranking the air bubbles is returning to the fuel filter.

After this check I guess that there is a leakeage in the filter, or before the filter.
But there is no clear fuel lines before the filter.

Is the first step just to change this filter? And maybe some sealings?

I did find a lot of chematics, but not for exact this model.
Do you have a link to fuel system schematic?
 

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Given that this is a Diesel, and that Diesels have little problem running lean due to their design, I'm guessing that fuel is getting to your high pressure pump. You may not be getting full power when you step on it, but the car should at least start. That said, yes, that leak should certainly be fixed.

I'm thinking crankshaft position sensor. When that goes, you're not starting that engine.
 

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So your low pressure pump is good. Low pressure lines are sold as an assembly, which is probably a good because they do brittle in time and also can draw air in everywhere.

That 'valve' is a measurement/bleeding connection for low pressure lines. It was used only short time in limited models, I never seen that in my cars, it's pretty futile there.

Filter rarely leaks, but black hoses top of it do. Do you have white clips or just jubilees? IF you have plastic filter housing, rarely that has been cracked, or cap seal can be badly installed.

I do not recommend trying to measure rail pressure with external fittings. Max pressure after all is 1300 bar though in idle its under 300bar...

CPS what cowboyt suggest, is a good guess but I think even your scanner should find a faulty sensor (yeah it might point to cam sensor or vice versa when sync is wrong in the start). Again, decent fault reader (SDS) would give 99% answer immediately, both CPS and rail pressure. In case your reader is not compliant to read even CPS, you have multiple problems, sensor and air in lines.
 

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Discussion Starter #9 (Edited)
I think my fault code reader can read CPS code.

Is there any place I can disconnect the CPS sensor to check this?

And is there any way to check the CPS with a multimeter?
My multimeter is a Fluke 289 and can log voltage down to 100 msec.
The meter also measures pulse width from 0.025 ms to 1250.0 ms
ranges.



Where is the CPS connected in the other end?


Attached is a picture from the code reader - data stream when cranking.
Is the RPM from the CPS sensor? Or is this coming for another sensor?

Icar.jpg
 

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I think my fault code reader can read CPS code.

Is there any place I can disconnect the CPS sensor to check this?

And is there any way to check the CPS with a multimeter?
My multimeter is a Fluke 289 and can log voltage down to 100 msec.
The meter also measures pulse width from 0.025 ms to 1250.0 ms
ranges.



Where is the CPS connected in the other end?


Attached is a picture from the code reader - data stream when cranking.
Is the RPM from the CPS sensor? Or is this coming for another sensor?

View attachment 2634309
Yup, the rpm reading means your CPS is working.
You should look at the fuel pressure regulator on the diesel rail next. If that is open, the engine will not start.
 

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Discussion Starter #11
What is the best way to check the fuel pressure regulator?

And still the camshaft position sensor can be broken? Is there a good check procedure for this? Where is the other end of the cable to this? Just to check that the cable is ok.
 

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What is the best way to check the fuel pressure regulator?

And still the camshaft position sensor can be broken? Is there a good check procedure for this? Where is the other end of the cable to this? Just to check that the cable is ok.
To check the fuel pressure regulator I undid one of the pipes leading to an injector, and blocked it with my finger. If you can stop fuel pumping out when the engine is cranked, there is not enough pressure. That was my problem a few months ago. It was replaced and the problem was solved....the culprits can be plentiful, but eliminate the easy parts first, i.e.
CPS - yours is ok
Cam sensor - replace with known working unit, I borrowed one from a friend for testing. It is only read during startup of the engine.
Fuel pressure sensor - on the front of the diesel rail (on my OM612 engine, yours is similiar)
If all these parts are in working order, you can check, with your multimeter, if the injectors are receiving electrical pulses when the engine is cranked.If not, you have an ECU problem...
 
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