ggh4

My E55 was running fine, maybe seemed like it wasn't running very smooth when idling. Parked it for a couple days , now it won't start. It will crank but not start.

No warning lights are on. Only code was a P20A2 - looks like it's a vacuum leak but that shouldn't cause it to not start. And if so it should start after clearing the code or disconnecting batter for a bit right? I tried that. I didn't see any bad hoses either.

I have replaced the CPS and the throttle body.

I plan to check the fuel pressure but did have fuel in the rail. I think I hear the pumps prime. With DAS I can't get the throttle body to move, I also don't see it move when trying to start, not sure if it should.

Anyone have any other ideas or maybe know the issue?

W21163

You check that vacuum hose on the intake tube on the driver side ? It towards the bottom of the tube

ggh4

Yea I didn't see an issue with hose. This is the one you have to disconnect before you can remove intake/filter boxes that connect to the throttle body right?

If I clear codes would a vacuum leak stop the car from starting?

tlambert

Check the fuel pressure at the rail with a gauge. Then check or replace the fuel pump relay

ggh4

Yeah no fuel pressure, found just one fuel pump relay. Is that correct for a 2004? Seems like everything is saying there should be 2.

bbirdwell

MY '03 and '04 have one fuel pump relay in trunk; the air injection pump relay is over the auxiliary battery.
MY '05 has one fuel pump relay and an air injection pump relay in the trunk.
MY '06 has two fuel pump relays and an air injection pump relay in the trunk.

ggh4

Hmm that interesting on the changes of # of relays. Well I replaced the relay and no luck. I took the backseat off and can't hear the pumps engage. So I'm guessing I need a new pump and filter

bbirdwell

Remember there are multiple variants of filter/regulators and pumps.

a) First and second-generation filter/regulators work with first-generation fuel pumps.
b) Third-generation filter/regulator works with second-generation pumps. This configuration requires adapter cables for both the filter/regulator and the fuel pumps.

Internal to the fuel tank, the fuel line connections to the first and second-generation fuel pumps are different. External to the fuel tank, the electrical connections are different. With the second-generation pumps, don't be fooled that the stock harness connecter fits; without the adapter cable one of the pumps will run backwards.

ggh4

How do I know which is which?

bbirdwell

Parts view here:
https://mbworld.org/forums/w211-amg/...ml#post7719667

Read this thread as it provides a bit more detail:
https://mbworld.org/forums/w211-amg/...-warranty.html

This thread by BoostedAero explains the bad things that happen to your air/fuel ratio if the adapter cable is not installed (spoiler alert: fuel pressure drops from >5 Bar to ~3.2 Bar at full throttle and air/fuel mixture goes lean):
https://mbworld.org/forums/w211-amg/...ging-asap.html
The Amazon links to photos in his post are good; be sure to look at the last link in his first post. All because the dealer missed installing the adapter cable.