dcsimmons

Our 2006 MBZ E-350 stopped all of the sudden headed down the interstate. The engine light came on a while back, but then went off. When it cane on, you could feel every distinctive stroke of the engine and so I suspected it was a camshaft sensor. Several months later, the engine light came on again, and scanning the codes showed a camshaft sensor going bad. By the time I purchased one, the problem went away again. But it came on again a week ago. It was my expectation to replace it when I had a free minute to do so.

I knew a bad crankshaft sensor would keep your engine from running, but I didn't think a bad camshaft sensor would. Nonetheless, I put the scanner on it to find out which one it was and replaced it. Nothing changed. Out of the possibility that I replaced the wrong sensor (there are mixed messages on which one is bank A, B, etc), I decided to replace them all (4 all together), and it still changed nothing. There were no other codes. I reset them, looking for a new one to show up, and nothing. No codes, nothing. Cranking it over does nothing. It doesn't even try to start, and no new codes. I don't believe a bad fuel pump or fuel relay always shows up (no feedback to the system), so I assumed the non-starting problem wasn't the camshaft sensor and headed to find out if it was getting fuel or not.

I checked and there was no fuel pressure on the fuel rail, so I suspected a relay since both pumps were replaced a year ago (VDO) and I couldn't imagine one going bad already. I checked the fuse and relay in the trunk, and the fuse is good, and the relay appears to be working fine as well. Both "switched" on poles went to 12 volts when turning the key on.

On the red wire of the main plug that goes to the pump (see attached picture), voltage switches off and on correctly with the relay, and I can hear the passenger side pump turn on and spin sounding normal. So it is a safe assumption this relay is working, and this pump is working or at least coming on.

I never hear the drivers side pump do anything, and I even purchased a brand new one, plugged it in (without putting it in the tank), and it makes no sound at all either. The passenger side spins normally.

So I have come to the following conclusions:

1.) The fuel pump (driver's side) senses whether it is in the tank or not and in gas. (I don't think this is it)
2.) It gets its power from a different wire than the provides the 12 volt to the other pump (the Red wire #2 on the plug) (Don't think this is it unless it gets its power from the pressure sensor plug)
3.) It is so quiet you can't hear it when it is running (Don't think this is it).
4.) It only comes on when it senses pressure form the other pump (passenger side) (I don't think this is it either!

I really am at al loss here as to why it isn't coming on unless there is some logic in the system that controls it beyond having 12 volts provided to it or not. It make sense that would be the case to control the pressure anyway.

Any help would be greatly appreciated! The car is just sitting in a T Hanger for now and I need it back on the road.

If it is of any convenience to others, I have attached some photos. One showing how to by pass the relay, another with location of the fuse and relay. The rest are self explanatory.

Thanks!

kajtek1

Would take a long time to analyze all your experience, but first thing that strike me is the fuel pump principals.
You have 2006 models, while I have 2004, but I think the tanks did not change in those years.
So the dual bottom tanks do require fuel to be pumped from passenger side to driver side where is main fuel pickup.
That is done by Venturi effect using returning fuel and I know that on those systems small misalignment makes the Venturi not working (friend drove like that for months when his engine run dry with about 6 gallons of fuel on passenger side).
So my first recommendation would be bringing a can of gas and fill her up.
Hopefully that will be all.

cmriv

If you are getting a INCONSTANT 12 volts at the main connector on the driver side pump, inconstant meaning it isn't 12 volts all the time when ignition switched on-it'll surge 12v then drop back down, and you have no fuel pressure at your fuel rail then i would presume your pumps are faulty again. But you state you can hear it coming on-do you see fuel cyphoning from the tank into the filter???? You should actually see fuel moving in the tank when pump is priming....

The vehicle cranks correct? crank but no start.... right?

Your rear sam controls your fuel pumps-the ME is what tells it to kick that relay over-maybe you need to do a voltage drop on pins 4 and 17 on the small connector of your ME but this may not be making sense to you....

cmriv

1 side is a filter and the other side is a pump.

dcsimmons

Thanks very much for the replies. The last comment, "and the other side is the pump, has always been a question for me, because I have wandered if there is only one as well. .

The driver's side "pump" in purchasing it was much cheaper with all of the goodies attached to it than the plane Jane pump on the passenger side, and it makes no sense. And in looking at how they work, it looks as though the small hose on the bottom of the driver's side pump that Y's off of the hose coming from the passenger side pump could (through Venturi) suck the gas out of the driver's side as well as pump it out of the passenger's side. But unless that is happening, there would have to be a pump on the driver's side as well.

Yes, the pump in the passenger side spins with the switch turned on, and then jumping the relay as well, it sounds very normal and spins at the same rate. I have a brand new pump I connected to the plug and it spins and sounds the same. If there is a pump on the driver's side, then it is doing nothing and even the brand new one I am showing pictures of connected does nothing either.

I had a crank shaft sensor go bad a while back, but if I recall, I still had pressure on the fuel rail. Am I correct a bad crankshaft sensor has nothing to do with the fuel pump turning on? If so, I am wandering if it is the culprit again. It was tricky getting the plug to connect right, but I get no codes thrown trying to start the engine and assume a bad crankshaft sensor would show up, even with the codes reset.

Thanks again for the replies.

kajtek1

The fuel pump is operated by computer and usually it comes for couple of seconds when you turn the ignition on, to build the pressure and then comes on permanently when computer sense engine turning, meaning CPS working.
Also for the record, Venturi nozzle is a pump.

dcsimmons

Can you tell me if in cranking the engine and it not starting, will it still generate the codes for a bad camshaft sensor and/or crankshaft sensor?

kajtek1

I don't know if anybody can answer the question. W211 is still a big mystery software-wise and I doubt even the high end MBUSA technicians know those things.
Older W210 did not have code for CPS work. It would display code when the circuit is broken, but that is all.
One rule of thumb for checking bad CPS (crankshaft not camshaft) was observing tachometer.

dcsimmons

What would the symptoms be of a bad camshaft balancer? The last couple of weeks before driving it, a vibration that I thought was coming from the tires was very apparent. But it seemed to idle normal, ran normal, but just unusual vibration. I actually put new tires on the front, thinking the problem would go away. It didn't. The engine revved out perfectly fine, didn't vibrate more as the engine was revved up, and so I just assumed it was still something to do with the other tires that weren't replaced.

Now I am wandering if my main problem is the camshaft balancer from a few things I have read. When the engine first stalled. It would at least try to start, as if it just needed a little more to keep going. But now nothing, doesn't even try to start at all. I hope it isn't a camshaft balancer, but am suspecting that it is especially because of the vibration that was felt before. Fuel does show up at the rail, it is just not under pressure.

kajtek1

I think you are jumping big guns without trying simple solution.
Did you fill' er up?
Make sure you have fuel pressure (I think it needs like 60psi, but check it) and than worry about other possibilities.

bbirdwell

There is no "driver's side pump" assuming you have a left-hand drive vehicle.


The "fuel sending unit" is on the passenger side (USA spec) and is an honest-to-God fuel pump. The "fuel pump assembly with integrated fuel filter" (aka "fuel pump assembly") is nothing but a fuel filter and pressure regulator located on the driver's side. Tear apart your old one and see for yourself. If you find different, please post for other user's edification.

dcsimmons

I have no doubt you are right, and they should not call it a fuel pump assembly. It has 3/4 of a tank of gas in it right now, and so I can't imagine adding gas to it will make any difference, but I have nothing to lose in adding a gallon or two. I am going to try that, and then if it doesn't work, take the camshaft sensors off and see if the circles line up telling me if my camshaft balancer is bad or not. I sure hope not.

cmriv

I would check the ME. IF your pumps are new and you are certain they are getting starting voltage then you probably have a bad ME.

kajtek1

Let me make sure I understand what you have done?
You have 3/4 tank of fuel, new pump, you jumped the pump to make sure it runs and you still don't have pressure at the rail?

dcsimmons

The car has 3/4 of a tank of gas, new pumps as of a 10 months ago. When the car stalled along the highway, I ran codes and it showed a "retarding camshaft sensor". I forget which Row/bank, but I came to the conclusion it was the one on the passenger side, exhaust sensor after scanning the internet. After replacing it, I thought the car was going to start because it acted like it wanted to.

You probably know better than me, but it looks like when you turn the key on, the starter stays engage for about 5 seconds on its on and then disconnects, or when it detects a certain RPM suggesting it has started, disconnects then. Right now, trying to start it, it just cranks over but doesn't appear to be trying. But immediately after putting in the new camshaft sensor, it was trying and I thought it was going to start. I turned the key, then let off the key and it kept going for several seconds...maybe 5 or so on its own. But in paying more attention to it, it appeared as though it was trying to start, but the starter was still turning it over. And when the starter would "time out", it would stop. In the olden days, this would have suggested a bad ballast resistor, but not here.

It was as if it had enough compression to run with assistance of the starter, but not on its own. So my suspicions were still camshaft sensor related, thinking possibly the camshaft opening and closing was such that it wasn't able to get full compression or power. I tried giving it gas during the time the starter was engaged and it appeared to be trying, thinking that if I could get enough RPM's, it would stay running, but it did nothing, didn't even increase the RPM when it was turning over.

No new codes would generate, nothing. But it wouldn't start. I unplugged one of the camshaft sensors to see if codes would generate from a bad camshaft sensor without the engine actually running, and it immediately generated a bad sensor. So I was at a loss as to what it could be, and didn't give the fuel a thought knowing it had new pumps and appeared to be trying to start. I eliminated anything having to do with ignition, because each cylinder appeared to be working the same.

In initially trying to find out which sensor it was, I got conflicting information, and so I decided I may have replaced the wrong sensor. And so knowing I reset the codes, and even though unplugging a sensor does throw a code, I decided to replace the rest of them and did. After that, nothing. It doesn't even try to start, but it won't throw any codes.

Knowing it has all new camshaft sensors, and now isn't even trying to start, I pulled the cover off the engine, removed the valve cap and used a phillips screw driver to push in the valve on the fuel rail and gas did come out, but no pressure or spray. My experience in the past with this is it should blow out a mist when you push in the valve, not just trickle out some gas. So I came to the conclusion it was fuel related all the time, that the code from the bad camshaft sensor was accurate but not the reason the car stalled.

I pulled the back seat out and removed the cover over the driver's side fuel pump. Turned the key on and tried to listen for it to spin, and nothing. Now I realize that even though as a part it looks like it has a motor, and is even called a "fuel pump assembly", it has nothing but a filter and pressure regulator in it. This has to be one of the best kept secrets, that there is only one pump, and it pumps out from the passenger side, through the driver's side. At the time, I didn't even listen for the pump on the passenger side, thinking that this one (the driver's side) was the actual pump that pumped to the fuel rail on the engine.

So thinking I had a bad pump, or it just wasn't getting juice, I checked the fuse, and it was ok. I removed the relay and shorted it out bypassing it completely. I still didn't hear the driver's side pump spin up (again, I know it isn't a pump now). The passenger side pump is just quiet enough that you have to really listen to hear it spin. I am sure it was running the whole time, but I wasn't looking for it to spin, and it was quiet enough I didn't hear it.

So the thinking was it had to be a pump, even though it seemed so unlikely one would go bad so soon. So I bought new pumps for both sides. I connected electrically the pumps, bypassed the relay and then for the first time heard a pump spin up, and it was the new pump sitting out of the car that I had just bought. And it was the passenger side pump. I didn't know the left side wasn't actually a pump yet.

I reconnected the plug to the installed pump (pump assembly on the left side), bypassed the relay, listened and heard the pump in the tank spinning. I checked, the pressure at the rail, and still gas just trickled out. So not knowing the left side isn't a pump, and not hearing anything spin up inside it, my belief was it was a bad fuel pump on the driver's side.

So I went to the parts store to purchase a new one. But before taking it, they were nice enough to check it out. They checked a total of 3 before coming to the conclusion they had 3 bad new pumps. That is a statement in itself as to how confusing this is.

After reading from you and one other, and realizing it has one pump, and is on the passenger side, I don't believe my fuel pump is bad. I don't have an explanation for why the fuel isn't under pressure, but fuel does get pumped up to the fuel rail. I think with the little amount of fuel that continues to trickle out of the valve, and with the rail valve being higher than the fuel injectors, there should be enough fuel in the injectors for at least partial ignition.

I am going back out this morning to see if there is any spark now, theorizing that the computer has shut it off because of a bad camshaft balancer / solenoid. I hope I am wrong, really do. But it makes the most sense after thinking about it, and especially the rough feel of the car driving down the road leading up to it stalling. Then the engine code reporting a "retarded camshaft sensor". It fits perfectly into the problem.

A stuck solenoid or bad balancer could definitely create the vibration. You can't imagine how much I hope I don't have a camshaft solenoid issue. I am going to take the camshaft sensors off, line up the crank, and then look to see if the circles line up correctly in the wholes. If they do, I'll have one huge smile on my face. If they don't, I'll be one pissed SOB and probably never by a Benz again. I have driven them now for 35 years continuously. But this will put me over the edge. The car has been maintained like you can't imagine. You can't tell it has ever been driven before. You could even eat off the engine, it has been maintained and kept clean that well.

Sorry for the length of this, but I hope it clears up any confusion.

kajtek1

It is a long story, but I think you should confirm you have fuel pressure at the rail before taking rest of the car apart.
For my 320 engine the harbor freight $19 gauge works, even it says "no Bosch"

dcsimmons

Good idea, I will do that for sure. I know it is lengthy, and you are a senior member didn't need 3/4 of the informaiton. It was written for people who don't have your familiarity as a kind of step through. I know form my own experiences here even being around cars all of my life there is confusion with this car, especially the fuel system.

I am also going to disconnect the battery from the car for several hours, out of the very small possibility that the computer will full reset itself if it is a problem. It could be a coincidence after disconnecting the plug to the one camshaft sensor, it doesn't even try to start now, But if in doing so, the computer shut things down, hopefully it resets everything back to defaults, even the solenoids if they are bad and will move. Thanks again for your help.

cmriv

If you receive customer reports in the above model vehicles that the engine cannot be started when the engine is hot but will start after the engine has cooled and there are no Diagnostic Trouble Codes stored in the ME control unit, check the signal that activates the fuel pump from the ME Control unit by monitoring pin 17 + and pin 4 on the small socket of N3/10 ME Control unit

I KNOW YOUR VEHICLE WONT EVEN START-BUT DO THIS SIMPLE VOLTAGE DROP AT THE ME.....

cmriv

i had a 203 chasis with a 272 engine that wouldn't even start-so the temperature theory went out the window-sure enough everything youve gone through i went through and it ended up needing a ME.... Its a simple test to rule the most expensive part out.....

dcsimmons

If the ME is what sends the signal to the pressure regulator on the fuel pump assembly, then I think you are onto something. The pump does come on, but the pressure is really low. However, it if just controls whether or not the fuel pump relay/ pump comes on, then then i am bypassing it and turning it on directly now anyway, so it wouldn't be the culprit. I am headed over to Harbor freight to at least get a pressure reading as suggested above.

cmriv

sounds good. spec should be 3-4 bar... and it is only suppose to drop a half bar every 30 minutes or so if i am not mistaken....

Daniel Olivares

I am having the exact issue as you are and have done the same tests. Do you have any update on what has happened?

cmriv

Was a verdict every met on this????

Scottyboy225

bump from the dead what was the cause of this issue as I am having similar issues now with an 07 E350

daniel43v

I am also having this issue, car will run with a little starting fluid, but no pressure at the rail, took the rear seat out and took off the Pas side cover, looks like a pump ,wires in there and all, and spins. driver side makes no noise, Should the driver side make noise?
Car will run when the fuel problem is fixed.
Somebody in this site hopefully knows.............
Dan
2005 e500