Hey everyone,

I have a 2006 Mercedes E350 with 140k miles, and it has served me well until yesterday. While driving home, I hit the curb hard with the passenger-side tire. About 5 minutes later, the car broke down and wouldn’t start.

• When I turn the key, the engine cranks and the car trembles, but it doesn’t start.
• After multiple attempts, it occasionally starts for about 5 seconds and then dies again.
• The tow truck driver suggested it might be a fuel pump issue.

I’m trying to diagnose the root cause before replacing anything.

• Could it be the fuel pump, fuel pump relay, or something else?
• What’s the best way to confirm if the fuel pump is the issue?
• If it’s the fuel pump, which specific part (module, relay, or pump itself) should I check first?

Any insights or troubleshooting steps would be greatly appreciated. Thanks in advance!

Always diagnose before replacing. If you have a scanner, you better get the codes, and follow the trail.

If there are no codes associated with fuel pump, and nothing else is obvious. You can test/diagnose the fuel pumps by checking the beginning of this video. It applies to the W211 as well. You can also rent a fuel pressure gauge, and there should be a Schrader valve on the engine fuel rail.
If you conclude your fuel pump is faulty, check FCP Euro

you need to replace CPS, crank shaft position sensor

How can I diagnose its because of CBS?

There are 4 alternatives here:
1 - Trial and error: throw parts at it.
2 - Get an MB aware scanner, read the error codes and follow the crumbs
3 - Find the electrical specifications of the part of interest, and with the appropriate instruments confirm the part is up to specifications.
4 - Let someone else figure it out.

The issue with the CPS is that it typically does not throw an error code. Unless you have some good diagnostic tools to actually verify the sensor is or is not working, sometimes it is easier, faster, and cheaper to buy the inexpensive part and swap it.

CPS is a common issue for this car.

Agree the crankshaft position sensor failure is a common issue, and symptoms are similar to the ones described; however, there are at least 7 possible codes when it fails.

For a summary of crankshaft position sensor failure and replacement
https://www.mercedesmedic.com/crank-...sition-sensor/

Thanks guys. My situation is kinda bizarre. Its more difficult to get one scan than buying parts online. I just replaced brand new Fuel Pump Relay and CPS. No use and even worse. I tried to start the engine too many times while pressing the brakes. Now it only tires to crank for half second and then stops. I believe the battery still has enough power. I want to give it last trial before dumping it. Any suggestion what shall I try? I can replace the fuel pump assembly, only cost $350 parts fee. But not sure if it's worth.

Believing doesn't guarantee anything. Make sure you have enough grunt on your battery, at least measure the voltage and get it charged. Getting to low voltage situation will just give you more issues to solve.

Cps code would be p0335. You can here the fuel pump wind when you insert and turn the key.