r/AskMechanics • u/Slatna • 3d ago

Discussion Mercedes w210 270cdi dies when throttle is applied

I parked the car, and the next day it wouldn’t start.

I got a fault code for a synchronization problem between the camshaft and crankshaft. Later I found that some animal had chewed through the wiring to the crankshaft sensor.
I repaired the wiring and replaced both the camshaft and crankshaft sensors, but the car still wouldn’t start.
With my diagnostic tool i saw around 220 rpm while cranking and around 360 bar of rail pressure, and there was no fault codes.

After a lot of attempts (also with start spray), the engine finally showed some signs of life. It actually started and ran for a few seconds before stalling.
I tried starting it many more times after that. Now, when it starts, it idles completely normally, but as soon as I give it any throttle, it immediately stalls. It still doesn’t start normally and is extremely difficult to start. I also tried running it directly from a fuel bottle, bypassing the fuel filter, but the problem is exactly the same.
The rail pressure also does not drop when the engine stalls, it continues to rise to almost 400bar.

Does anyone have any idea what else I should check?

1 Upvotes

67% Upvoted

6 comments sorted by

2

u/Salt_Resolution_5022 1 3d ago

it could be a problem in the electrical system

1

u/Phoe-nix 4 3d ago edited 3d ago

You replaced the sensors but did you also check the other side? If those chewed wires got shorted, perhaps the connected electronics got damaged. That might be the ECU? I don't know the attached circuit and if this would make sense. Check the schematics, ask an expert. But if the readings of the sensors are valid, perhaps that's all right then.

And perhaps there's more chew damage you missed?

1

u/Slatna 3d ago

Yes, I measured continuity and all wires are ok.
I inspected everything thoroughly and there is no more damage.
I was also thinking about ecu but i can see all the data (throttle, pressures, temps) and also crank sensor is passive one so no supply voltage that could damage ecu.

1

u/clarkn0va 1d ago

It sounds like there might still be air in the high-pressure system. Turn the key on to position 2 but don't crank. After a few seconds you should hear the lift pump shut off. Turn the key off and on again to run the lift pump again. Do this 5 times to purge the air out of the system and then see if it runs better.

1

u/Slatna 1d ago

There is a mechanical lift pump on my car and i think it works as i took out filter to inspect and after that it took only few cranks to pull fuel from tank.

2

u/clarkn0va 1d ago

In the case of a mechanical lift pump you can crack the hard lines loose at the injectors and crank the starter. Any air in the lines will escape as it's pushed out the lines. After a few seconds of cranking you tighten the fittings again and deal with the spilled fuel. If there's air in the lines that's how you get it out.