Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
I have a feeling that the fuel pump is seized but there are some basic checks that can be performed without going underneath the car first. There is a fuse for the fuel pump under the rear bench seat. It can be accessed by lifting up the bottom cushion. There is a small button/lever under each front corner of the bottom cushion, just push on the button/lever while pulling up each corner one at a time. Now the seat should be able to be lifted and pulled forward. On the passenger side by the battery is the rear fuse box. Check fuse #6 for power or at least to make sure it isn't blown. If the fuse is good, the next check would be at the fuel pump relay. It is attached to that same fuse box. I've attached picture #1. If you are not comfortable using a volt meter or jumping electrical terminals, then I suggest you just replace the relay. If you can, make a jumper wire by crimping spade ends on a wire and jump terminals 30 and 87 on relay socket. This will force power to the fuel pump. If there is still no rail pressure, then either the wiring to the fuel pump or the fuel pump is faulty. To confirm if the wiring is intact, you will have to go underneath the car, and remove the plastic panel covering the fuel pump. There are just three 10mm nuts securing the access cover located just in front of the drive's rear wheel/under rear door area. From there, a simple voltage check at the fuel pump could be performed to confirm the wiring is intact. I've attached another picture with this one being the fuel pump location. The fuel pump is the smaller, skinnier one next to the fuel filter. You could check for power and ground there or just tap/hit it with a metal object which will sometimes unstick the pump. Let me know if you have any more questions or need help, thanks!