Hi,
I have C230 Kompressor, 2002 (W203) with 2.3L engine.
Last month I replaced the Fuel Level Sending unit (it is located under the rear seat, on the driver side). To do this, the fuel pump should be pulled out of the tank as well (it has hoses and wires coming to the Sending unit that need to be detached). Since this is not very complicated job, I did this work by myself.
I did not disconnect the battery nor remove the pump fuses to un-power it.

Almost immediately after this replacement I noticed that my engine does not start as quickly and reliably as it was before the replacement. Especially after long stay, e.g. overnight.
Now, I have to rotate the started for 5-7 sec. before engine starts (previously there was 1-2 sec. time).

There is a valve on the tip of the fuel rail, close to injectors (it looks like a small pin). Previously, when I had pressed this valve, even in the morning, the fuel under slight pressure started leaking. Now, when I press it, there is nothing at all. So, it looks like the rail is completely dry. That's probably why it take some time for engine to start: it pumps fuel into the rail.

I wanted to ask what would be the reason that gas is not staying in the fuel rail anymore? Could I damage the fuel pump or its return valves when reconnecting the hoses? Any recommendations?
Thank you for your help!

 

Hello Volunteer,
I read your post and I have the same problem with my C230K 2002 coupe right now. I need your insight to know why? Let me explain. So, I replaced the fuel pump myself a couple of years ago but I did not replace the fuel level sending unit even though it was giving issues. Sometimes, it would read empty when I had a full tank. After replacement of the fuel pump my car would not start. I took it to a local mechanic shop and he hired and electrician to go to his shop and fix it. When I got the car back and the problem was fixed. I asked the owner of the shop for information about what caused it? He couldn't tell me what the electrician did to fix the electrical issue. Now a few years later I decided to replace the fuel level sending unit and I did the same mistake as you did. I did not remove the fuse to the fuel pump nor the relay.
I also decided to clean out the fuel tank to remove the dirty film that had accumulated over the years.
But I had a problem getting fuel to the injectors rail line. The problem is that the fuel pump or fuel level sending unit are not energized. I checked the fuse and relay and they are okay! eagain to fix that problem. I would like to know if you found out what caused that problem and did you fixed it yourself?

Thank you for your time and input.
Billy Herrera

 

It sounds like the issue is related to fuel pressure retention. Here are some things to check:

1. Fuel Pump: The pump's check valve may be faulty, causing pressure loss in the fuel rail.
2. Connections: Ensure all hoses, wiring, and seals around the pump and sending unit are properly connected.
3. Fuel Pressure Regulator: A faulty regulator could cause pressure loss.
4. Fuel Rail: Inspect for leaks or issues with the connections.

To diagnose, check if the fuel pump primes when the key is in the "ON" position, test fuel pressure with a gauge, and inspect the check valve. If needed, replace the fuel pressure regulator.