scoobertdoo

So yesterday morning after a long trip the day before the car would not start.
I found the fuel rail to be completely dry.
today I jumpered the fuel pump relay, and behold the car started.
I ordered the new relay, but when the car started, it was missing quite badly. I ran the engine for a while, and revved it up to 2400rpm where the miss is almost not noticeable, and let it idle, and still it runs rough. Now I am puzzled.
What does the fuel relay have to do with the car running rough?

scoobertdoo

No help on this?

scoobertdoo

Is the fuel pump relay used anywhere else on the car so I can swap the fuel pump one with a normal one and see if it works?

scoobertdoo

So its not the relay. I jump the relay, and it works, but I swapped the relay for the horn relay, and it didnt change the result of no running pump. The good news is the fuel rail filled up, and with the relay jumpered, it runs fine again.

PLEASE what else could cause this?

cmriv

What are you asking? You are answering you own questions pretty much. It running rough may be a dead coil and or shytty gas. does vehicle crank with relay installed? Crank as in try to start but wont turn over....

scoobertdoo

The car will crank with relay installed, but will not fire.
The pump is not being turned on without the jumper wire.
When the jumper wire is installed, I can drive it normally.
The jumper wire is working, so i guess its not a pump plug issue?
Just trying to figure out what send the signal to the pump to run, I will multimeter it tonight to see if it is sending a signal at all.

scoobertdoo

So the result are as follows.
The activation prongs on the relay are showing 10 volts.
When going from the ground on the activation prong to the pump wire I also get 10 volts.
When I go to the ground bolt next to the trunk panel I get 14 volts.
So does this mean I have a bad ground?

Rocman8

Get a DAS machine hooked up and let's see what codes are present.

scoobertdoo

Wish I had one.... Still looking for an indie in St Augustine who has one, have yet to find anyone.

scoobertdoo

While sitting here thinking about the issue....
The day before we took a 400 mile trip, and went thru a lot of rain on the way home.
Then the next day it didnt start. What is the chance that I just hook up a new ground to the back of the box that it would have enough voltage to work?

scoobertdoo

so update, I ran a small wire from the ground on the relay to the trunk latch.
Car started.
So this whole thing was a ground issue???? Going to wait for the car to run normal again, then call this issue solved. the fuel rail is still draining after its done running for some reason.
Now I have to tear out the trunk lining, and run a proper ground wire I guess.,

hondaguy601

scoobertdoo,


how did you ground the wire? I'm having the same no voltage to the fuel pump problem. I also have to use a jumper wire for the fuel relay rear sam. I tested the pump and relay and they are both good. Thanks for your help in advance!

scoobertdoo

Car went to the junk yard. Parts are so expensive, and labor too. So many electrical issues, and so much money wasted on a pos car. One will start, and you will have the next issue, and the next.

rodneypierce

Scoobertdoo you bought your car against the advice of everyone here on the forum. Had no pre purchase inspection done (which everyone told you to do). You cant fault anyone but yourself for buying a lemon. Against everyone's advise even.

scoobertdoo

I have run into a ton of people since then that all say the same thing. Never buy a merc out of warrantee. I keep hearing issue after issue. I guess the old 300 diesels were the last ones anyone should buy that will last a long time. I keep hearing about electrical gremlins, constantly. I do however love the youtube video about buying one from carmax with an extends warrantee. One guy said he cost them $14,000 in repairs over 2 years :P

cmriv

Dude is smart. X-warranty companies will foot the bill for most issues. however you made your bed so unfortunately you have to lay in it. These cars aren't that bad. sit in a 40 year old honda or chevy then sit in a 40 year old merk, big difference. however wish you woulda said you were taking it a junkyard haha

Mercedes: first vehicle ever made
Mercedes: biggest POS when something is wrong to the average owner
Mercedes: greatest thing ever when nothing's wrong

its all an opinion ha. lemonsqueezyyyyyy

Rocman8

Common issue withe the 07 273 engine especially in the 211 and 221. Engine module faulty not grounding the fuel pump relay. Did you even have someone who knows these cars well like a dealer with an experienced Mercedes tech look into this at all or this was all your own doing?

rodneypierce

Rocman, this was all his own doing. He didnt listen to a single thing anyone told him to do.

hondaguy601

Rocman,
When you say engine module, are you referring to ecu? Mine , works fine usually after I use a jumper wire in the relay spot. I have the seat out and have been finally listening to the pump prime one I place key on position 2. Seems like it's working now, I'll keep testing it for the next few days.

Rocman8

Yes I am referring to the ECU right on top of the engine. The 07 had an issue with it not sending the signal to the relay.

hondaguy601

Rocman,

Mine is a 07 e550 with 107k on the dash, could I just create a ground wire for the relay in the trunk? Buying another ecm is pretty expensive for that model. Are there any write ups on the remedy, furthermore how were you able to fix yours?
Thanks a bunch brother!

Rocman8

I've never fixed this issue any other way besides replacing the engine module.

hondaguy601

Did you get your ecm rebuilt or did you purchase a used one? Also did it require reprogramming?

when I use a jumper wire, have the engine running for 10-15 minutes ( if I plugged in the fuel relay it would then prime and start ) however, by the following day, there would be no signal to the pump meaning I guess no ground to the relay. (Both ignition power and 12vconstant has power) Did you have these symptoms as well? Thx bro

Rocman8

Sounds about right but it's been a while. My suggestion is to have it officially diagnosed at a dealer since that's where you have to do the module anyways. A new module will need to be programmed and you cannot use a used one.