drpete_amg

Have been chasing this issue for some time... any help or suggestion is much appreciated.

Car not starting. Narrowed to fuel pumps not running. Specifically, pump doesn't prime when ignition is turned on/cranking. On a very rare occasion after many many times turning ignition on and off the pump will audibly power and prime after which the car will start and run fine until it sits for some time after which it will not start again. No CEL, OBD codes or other warnings...I do not have access to Star Diag.

Due to fuel leak at cracked plastic connector on left pump (fuel smell issue!) and suspicion of issues with right pump I replaced both especially given mileage (75k). General performance was MUCH improved and fuel leak resolved. However, starting issue remained. I replaced fuel pump relay in rear... same results. I have checked voltage at 4 wire connector to right pump...no power when helper cranks engine. HOWEVER, when I disconnect the plug and manually apply 12v to the pump directly it immediately starts pumping and the car starts and runs perfectly. After idling for a period, re-checking the voltage at the connector yields 14v. Once voltage is measured I can re-connect connector and pumps power and car starts and runs normally...again, until car sits for some time and starting problem returns.

Only other suspicion/concern is that the shielding on the 4 wires into plug on right pump are split from being bent under metal pump cover. Suspect this happened after dealer finally replaced tank (fuel leak/smell!!!) It is only the shielding and the wires appear fine and obviously carry voltage after above procedure. I have taped each to assure no shorting.

Just FYI...I replaced CPS prior to this current issue due to starting problems and OBD code. That particular starting problem was resolved with new CPS.

Thanks! Again, any help is appreciated.
Doug

2005 W211 E55 wagon

Plutoe

Well if you don't want to have the car tested for a faulty fuel pump---then go by your gut feeling and replace the so called faulty fuel pump--but don't come whining back that you change the pump that you still have the problem!!

drpete_amg

Thanks. Unfortunately, the pumps needed to be replaced despite the starting issue. So it made removing the pumps from the equation easy . Thus I am still in pursuit of a solution.

purplegrog

Did you check your fuel pump relay? Just conjecture here, but maybe the relay is intermittently failing.

drpete_amg

Purplegrog... I had actually replaced previously the relay that I had been directed to in the left rear SAM of the car (with no change in results). HOWEVER... thanks to Rocman8 I have since learned that the actual fuel pump relay is in the right rear corner of the car BEHIND the sub-woofer. I just removed the sub, discovered the proper relays and replaced it with the part purchased previously and thankfully it fired right up and is running great! Great thinking and suggestion...you were right on! Thank you for taking the time to respond and your willingness to help!

SOLVED...https://mbworld.org/forums/w211-amg/...sues-help.html

konigstiger

Thought it best to mention e55 relay location differs from straight 211 as noted in rear SAM relay assignment, see here http://workshop-manuals.com/mercedes...on/page_15871/