rog2961

Tank was replaced 2 years ago and every now and then car would have trouble cranking. Replaced cps couple months ago and it seemed to clear the issue up for a bit. Now today it wont start. When I turn the car on the pumps are turning on. The wiring harness is the correct part number and not the older one. I pulled the fuel tank tops off and it looks the pumps are priming but pressure isn't building up on the drivers side. When priming, the hose that leads back to the passenger side and dumps gas back has a bunch of bubbles, but checked the connection on the filter side and it looks ok. Dealer is already giving me crap saying how they wont cover it. My warranty is up on this month on the fuel tank from the 15y extension. Anyone ever have this issue?

N_Rob

I had an issue that mimicked the CPS a few months ago. Like you I replaced it and it didn’t do anybing. bbirdwell tipped me off about the fuel relay in the trunk possibly being burnt out. That was my issue, might not be yours but worth it to check because it’s extremely easy. It’s behind the trunk liner on the passenger side. If it’s really bad you might be able to see the burnt plastic on the white part between the relay and harness. I have pics on my thread of what mine looked like.

bbirdwell

Been seen multiple times on this forum.

Connect a fuel pressure test gauge to the schraeder valve on the passenger-side front of the fuel rail. Should pressurize to 80psi +/-3psi at idle. Fuel pumps energize for one second at key on then shut off until the motor electronics receive data showing the engine is turning over (safety feature in case the engine stops running).

Inspect and replace the fuel pump relay (only a few $ for a new one) under the trunk passenger-side panel and inspect the fuel pumps' connector for signs of overheating both on the outside cover and on the fuel pumps themselves. While you are pulling the relay and replacing it, pull the 30-amp fuse and ensure the metal tabs are not corroded; mine looked pretty bad but some emery cloth cleaned them up.

Try this thread:
https://mbworld.org/forums/w211-amg/...intenance.html

rog2961

thats odd i only have the one relay on that side with 4RA 007 791-00/A0025421319 but no 30 amp fuses at all. MInes not getting any pressure are all. When I attempt to turn the car on the fuel pumps run for about 5-7 seconds then shutdown.

bbirdwell

Ah, I just noted you have a 2004. In that case, your secondary air pump relay is over the auxiliary battery and only the fuel pump relay is in the trunk; fuse for the fuel pumps should be close at hand to the relay. On the early model 2003 the relay had the built-in fuse holder. That changed to a separate fuse holder between March and 1 September 2003. On the 2005 model, the secondary air pump relay and its fuse were moved next to the fuel pump relay and its fuse, thus my photos of two relays.

Again, replace the relay and verify the socket is still good; quite often the relay overheats badly enough you have to cut the wires back and re-wire the socket and connectors for the relay.

rog2961

replaced relay and the socket looks good still no start. When I try to start the pumps just prime for a couple seconds then shutoff. The fuse by the battery looked good too.

rog2961

I also measured pressure at the rail and I am getting the full 80psi when I turn the car on, but no spark. New battery from a month ago.

N_Rob

Priming for a few seconds and then shutting off is normal I think. If you say no spark, have you checked your plugs and coils?

Pmarino

What happens to the fuel pressure when the starter is turning the motor?
When I had a clogged fuel filter, it would build pressure when key turned on to prime. Then when I cranked it, the fuel pressure would drop to nothing and it would not start.

Warning this is a controversial quick roadside diagnostic; If I want to know if it's spark or gas.... I spray a quick shot of brake cleaner into the throttle body while the starter is turning over the motor. If it fires momentarily.....It's a fuel issue. If spraying does nothing.....it's not getting spark.

rog2961

the pressure does drop down to 40 or so after it hits 80. i dont even hear the starter clicking. car doesnt crank either

Pmarino

Sounds like you have multiple issues. Got to trouble shoot the starter first.....Battery? Current to starter? Ground straps?

rog2961

the fuse looks good for the starter. the pressure drop on the gauge was probably from the crappy gauge i have, it leaked a little once it hit 80 psi. Dont think the pumps are the problem. Is there a relay for the starter? Before it died it turned over once. It doesnt even click when i turn it on

Pmarino

https://mbworld.org/forums/e-class-w211/589511-w211-starter-does-not-turn-intermittent.html

rog2961

replaced starter relay and nothing. thinking its probably the starter.

Pmarino

Or the solenoid. Not sure you can get a big screw driver or pry bar on the starter from the passenger right side engine bay. If you can, try giving it a smack while it's trying to start.(old school) Did you try starting it in neutral with your foot on the brake?

rog2961

jumped the starter and got nothing, ordered a new one. Was probably from cranking too much when cps went a couple months ago. Starter just got weaker and weaker over time which showed up as long cranking every now and then.