sy-1177

So my car has been issue free since I bought it used last fall. It currently has 55k miles on it and just had its first issue for me last night. I drove it home from work, droped off my kids, got back in it 5 mins later and the thing won't start. It turn over fine and almost cacthes for a second but just keeps cranking for about 5 seconds. No check engine lights or anything. First thought was a fuse or fuel pump issue. I checked all the fuses and they looked good. I then checked the shrader valve on the fuel rail, with the key on (primed) I hit the nozzle and gas came out so I assume that its getting fuel. I actually checked this a few different times and each time it had good pressure comming out.

I'm not really sure where to look next. My guess is ignition, but what? Anyone have a similiar issue like this?

johnand

Don't dismiss the fuel pump. We have had a rash of 07's with premature fuel pump failure lately. Get a fuel pressure gauge and make sure the pressure is in spec. Could also be a CPS, as this is a common problem part too.

sy-1177

You know, I'm hoping that it is the pump just so I don't start throwing parts at it. The first time I tried to start it (when it didn't start) it chugged for a couple seconds like it was starving for fuel, that why I initially thought it was the pump. Other times it just cranked with no signs of life. I'll try throwing a pressure gauge on the rail and see where its at. Whats the stock fuel pressure for these anyways?

johnand

3.7-4.2 bar.

sy-1177

Thanks for the info man, I appreciate it!

chmura

I'm curious to know what the issue was, did you find out yet?

LILBENZ230

Damn, another one? A bad batch perhaps?

sy-1177

Ok, did a little more work on it today... still not exactly sure if its the pump(s) or not. So I tried to put an OBDII reader on it last night, it wouldn't sync up with the computer, and i'm not sure why. We tried the scanner on another car just to make sure it worked and it was fine on the other car. Could my ecm possibly be bad?

Then, I put a gauge on the rail. Primed it, and cranked it, no fuel pressure at all. I pulled the back seat and pulled out the 12v test light to test power. On the primary pump, I only saw voltage on the red wire of the smaller plug, and it was b arely enough to light the test light. Maybe 4-6v? I tested the secondary pump wires and saw crank voltage accross only one of those wires. I thought it was strange that I didn't see anything though on the main pump wires. (besides that very dim light on the red wire)

So, where to look next? Fuel pump relay maybe? Should I throw 12v directly at the pump to see if I can hear it fire up?

johnand

You are on the wrong side. Pump is on the passenger side of 07's. There is only 2 wires on the pump, brown and black. Brown is power, and black is ground. You were testing the sending unit. Check out this post for a picture of the top of the pump: https://mbworld.org/forums/4489063-post71.html

sy-1177

Oh, well that explains it then! I called the dealer just to see if there were any recalls for it and they told me that it had 2 pumps so I assumed the drivers side was the pump side since it had more going on. It's good that I saw juice at the plug then so it does appear to be a bad pump. I saw in another thread that u got ur pump from parts.com correct? I looked it up and saw it was 220 for my car, that seem reasonable? I better get one on order here very soon as this is my daily driver and I've been driving my gn in the meantime.

Norwichdelta06

im honestly leaning towards the CPS. I never done it on a MB yet but the syptoms you describe sound like its the CPS.

sy-1177

Well if I throw 12v at it from an external source it should fire up the pump correct (essentially bypassing the ecm) which would eliminate the cps?

johnand

My pump was $173 at parts.com. Price must have went up. That sounds reasonable. Make sure you get the OEM pump regardless of where you get it. There was another member that got the Bosch pump that is listed for an 07, and it was the wrong pump.

There are not 2 pumps, but there are 2 sending units. The drivers side module, is a sending unit, and fuel filter. The passengers side module is a fuel pump and sending unit.

Generally I would agree with you, but just take a look at all the recent posts lately about 07's, and early W204's with premature pump failure. Obviously MB had a bad batch of early pumps.

Proper diagnosis by the OP, with a fuel pressure gauge will determine if the pump is bad. Frankly replacing the pump is easier than the CPS. I have done both, and the CPS is a PITA, and the pump is a cakewalk.

johnand

I wouldn't do that. I would do the proper test by hooking up a fuel pressure gauge. While cranking you should have 3.7-4.2 bar. If you don't then check if you have 12V to the pump while cranking. If you don't have pressure, but have 12V at the pump while cranking, the pump is dead.

sy-1177

I did check, I have 12v at the pump while cracking. I watched the gauge on the rail and it was stuck at 0 the whole time. (Shrader valve was removed too)

sy-1177

Pump is out and I threw 12v at it and it worked. Now does that mean its good or maybe on its way out?? I don't know. After reading this thread, https://mbworld.org/forums/c-class-w...re-rail-2.html I saw that someone else threw the tested good pump back in the car and it started up. I'm thinking about trying it and see what happens.
Part number on the bottom of the unit is A2C53185313

johnand

Just because it runs when 12V is hooked up outside of the car doesn't mean, it will pump enough fuel to the proper pressure inside the car. The fact that you had 12V while cranking and 0 pressure at the fuel rail, means the pump is faulty. Only other slight possibility is the fuel filter in the drivers side module is plugged. I think the poster in that thread and you both, have a pump on the verge of complete failure.

sy-1177

Yeah, i'm with you on this one. Going to order a new one now. Thanks again for all you help with this!

LILBENZ230

Did Mercedes accidentally get a batch of BMW HPFPs and put them in these cars or something? The 135i is on its second fuel pump in 33k miles and is already having some long cranks again.

sy-1177

Its funny you say that, my dad has a BMW 335xi and he mentioned that model having some fuel pump problems as well. Not his particular car just yet, but he's read about it online.

Moviela

Usually German cars connect brown wires to ground, is this correct John?
Have you had time to determine the failure of your pump?

I mention this because I recently had a problem with a 100KW lighting generator with a similar in-tank pump. There was 12V at the connector and you could hear the pump whirring, but no fuel pressure. I had a new pump delivered and noticed the interior wiring of the assembly was red and black with a + on the motor terminal of red. This was opposite of the external tank wiring of brown and green. Someone had jerked on the wires and pulled the terminals out of the housing then stuffed them back in backward. This made the pump motor run backward, thus no output.

sy-1177

Car is fixed!!! After ordering a pump from 2 different places and having it get canceled due to out of stock I broke down and paid a little more at parts.com. Now what made the transaction reassuring was that I went through the catalog, and got the pump ordered ($280 shipped) but they ask for you vin on checkout. So I entered the vin and get a response the next day that I ordered the wrong part and that I need XXX###XXX and its only $160! Cha-ching!! Got the ump today and took 20 mins to install. Car fired right up on the first crank! Thanks for everyone's help here and if anyone else needs one, go to part.com. It turned out to be an OEM unit from a dealer in IL actually. $180 to my door!

Carsy

Good stuff .Thanks for the update.

Glyn M Ruck

Sheesh! another pump.

Pleased it's fixed.

pcy

my car is also made about the same time. I have a feeling, the fuel pump on my '07 C280 may not be too far from needing to be replaced.

I am glad that I've been reading this thread. I know exactly what do when the time comes for me to replace the pump. :-)