eb88

Good evening everyone,

I'm writing this message on the side of the road waiting for the car to cool off or come to its senses. The 2002 c32 has been great with the exception of sometimes loosing power by shutting off the supercharger. Recently the car died on the freeway coming home from a short trip, I towed it home, replaced the crankshaft positioning sensor after reading these forums, and it drove wonderfully yesterday.

Today on the way back from the grocery store, the car slowly died in an intersection and thankfully had enough momentum to get me to the side of the road.

Possible problems? The car performs great otherwise and has a 1 week old battery. Could it be the intercooler pump? It only seems to happen after engaging the supercharger, not when staying out of boost.

Thanks!

Kostas20

Did it sputter and die, cut-out immediately, go into limp mode (no effect by pressing accel pedal)?

When trying to start it back up, does it try to turn over, or does it not engage at all? Have electrical power?

eb88

Thanks for the reply.

When it died this latest time, the engine was still running but the pedal had no effect. It slowly spotted for about 5 seconds then quietly turned off with the battery light flashing on the lid screen.

Sitting here and trying to start it, the starter turns freely and fast, but there is no sounds off combustion. This happened last time as well, when I got home about 40 minutes after I pulled over initially, the car started up with no problem.

swatty

Maybe a crankshaft position sensor

Rocman8

Did you use factory sensor or aftermarket? Your IC pump won't cause a no start. Pull the codes and see what there is.

eb88

Just replaced it, see first post.

I used a BOSCH factory sensor. The car had no codes when it died last time, nor does it have codes now. I was confident it would be the CPS because people often had these symptoms with no codes (like I had).

Kostas20

Lift up the bottom of the back seat - you can grab it from the back of the seat (where the bottom of the seat belt buckles are tucked into) and pull it up and forward - then put the key back in and go to the position right before turning over. You should hear a whirl from the fuel pump kicking in and priming the fuel lines for a second. You should be able to hear the whirl with seat up and all the doors close while sitting in the front seat to turn the car.

Basically this is an easy way to see if your fuel pumps are sending fuel to the engine. Given the car is turning over but not starting, fuel at the engine is the first check. If the pumps whirl that rules out the pump and relays since it is engaging.

Agree with above comments, it really does sound like your CPS again though.

eb88

Thank you, I'll definitely try this tomorrow. After reading your comments and other forum posts, I found and decided to buy the fuel pump relay on amazon for about 9 dollars shipped.

I'll be sure to keep this updated.

eb88

Well I couldn't wait to do such a simple check so I went outside, pulled up the seat, got in the car and could not hear a whirl (assuming it should be continuous). I even hovered over the plate housing the pump and didn't hear anything. I pulled and switched the #5 fuse with another fuse and it did not turn on. I pulled out and tapped the relay a few times, still no pump engagement.

I'm hoping it is a relay at this point, we will hopefully find out soon! Car has 180k on it, so if it turns out to the be the pump, it probably needs replacing anyways.

Kostas20

if it is your fuel pump i had something similar happen to me

https://mbworld.org/forums/c32-amg-c...c32-owner.html

with the seat lifted on the driver side you will see two electrical plugs in the circular entry to the fuel tank. the larger plug is your fuel pump power. pull it and check the integrity of the prongs. my ground prong was melted.

also the fuel pump whirl should only last a second when going into key position two. it just primes the lines with pressure for when you turn the key to start.

if you have it at home now you can do a full confirmation of fuel at the engine by removing Schroeder valve on passenger side fuel rail.

PJmak

The last time my car had those exact symptoms s when I put in a faulty MAF sensor but it might be a different case for you since the C32s dont have one?

Kostas20

yes, we do not have a MAF.

Plus I believe any issue related to that (throttle body, etc.) would throw a code with, at a minimum, a malfunction in the throttle body circuit.

eb88

Primed the pump and pushed in the valve on the passenger rail, it was a dribble of fuel. Car turned over, started for a bit then died.

Checked the pumps wiring and no signs of burns or shorts. I was lightly tapping the pump with a rubber mallet and was able to get it to start and run for about 10 seconds. Guessing it is the pump at this point.

ItalianJoe1

Yeah it's almost always just the pump. A failing pump will draw excessive power and can burn a relay or fuse, but the pump itself is bad.

Easy to change on these cars, and not terribly expensive.

eb88

Thank you, I think I'll definitely be buying a pump soon but.... the plot thickens!!!

I began to notice that after tapping the pump with the mallet it would start up but would die about 5 seconds later. For whatever reason, I decided to pull the passenger access panel and give that side a few love taps.

Oddly enough, when I started the car this time (probably about 20 times now in total) it started up perfectly and was able to drive around the block. The car still runs oddly (accelerator pedal doesn't have the same linear relationship to acceleration) but I'm wondering if there is sediment or something in the tank. Adding belief to this argument is that last time the car wouldn't start but after a 15 minute tow home, it started without any problems (cold before and after the tow).

Fuel filter was replaced about 10,000 miles ago so I doubt it is related to that. I'm planning to search now about the fuel system set up, but it quite possibly could be the unit on the passenger side.

eb88

Hmmmmm, I may be pulling the sending unit to potentially check this out. I was getting barely any fuel to make it around the block so if the hose between the pump and sender unit is broke, I can see how I get such crappy fuel delivery.

http://www.benzworld.org/forums/w203...em-solved.html

Kostas20

The c32 has two fuel pumps. An auxiliary and a main pump (the aux fills the little bucket that main sits in) and are both on the passenger side access panel. The power to the pumps goes through the level sending unit on the driver side access panel and gets to the pumps from inside the fuel tank. Yes, horrible design, but that is the way it is for some reason.

If you had more luck with getting it to run after hitting the passenger side then your main pump is probably toast. Running on low fuel in hot ambient temps can really accelerate the lifespan of the pumps from my understanding.

The good news is, if you are fairly handy, replacing the main pump can be done relatively cheaply. it is time intensive though so if you have it done by somebody labour will hit you far more than the part.

eb88

Thanks again for all the information, I appreciate it.

Well with a full tank of gas, I decided I would remove both units and just replace them as I'm sure they came with the car. The design is indeed horrible, I'm not understanding why there is so much needed for such a simple process.



I just bought the pump off amazon and the fuel pressure sending unit off autohausaz.

eb88

Happy Friday MbWorld,

I replaced both the fuel sending unit and the fuel pump yesterday with Bosch units. Install was fairly simple and straightforward with the hardest part making the gasket seal perfectly without pinching. The pump I bought did not have an input for the auxilary pump (which feeds the main pump) so I left it out and the car runs better than when I got it.

I'd highly recommend anyone with an OEM pump pushing 200k think of the possibility of replacing both units.

Take care and thanks for the help,
Ryan