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2006 CLK 350
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Discussion Starter #1
I have a 06' CLK 350 where it suddenly went to hard starting to only starting when cold. Now the car does not start at all. When the car was running the fuel pressure was around 30 psi. I suspected a bad pump but measured the voltage to the pump between the two thicker wires (solid brown wire and black/green wire) The voltage was .5 volts with the key in the on position and 10.75 volts when attempting to start.

Does anyone know where the fuel pump relay location? Here are some images of the project.
 

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Coupe/Convertible Forums Moderator
CURRENT: 2011 SL550, 2011 C300 FORMER: ML350, CLK550 Cabriolet, C240, ML320, 300TD
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Fuse #4, rear SAM.
 

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2006 CLK 350
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Discussion Starter #3
Did you mean the rear fuse box?

Have a factory cd rom on order for the car. Until then, I am making an educated guess!
 

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2004 CLK 240 Coupe
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Hi - if you go to the W209 forum stickies, you will find a thread that covers the location of all the fuses & relays on your car.

http://www.benzworld.org/forums/w209-clk-class/1629567-all-fuse-relay-box-details-w209.html

I found the Fuel pump relay as Relay A (N10/2kA) located on the rear SAM N10/2.

Earlier (pre-2005) CLKs had the fuel pump alongside the fuel filter located under the car, just ahead of the left rear wheel. From 2005, the fuel pump has been moved to inside the fuel tank, and the filter has remained in the original location. These internal pumps are very reliable, and are not expected to fail. Of course if you have no pressure on the rail, it could be a failed pump - or maybe a blocked fuel filter.

I think that the fuel pump is powered when the Ig switch is in posn 3 - but I have never heard mine running and it is not inside the tank, as your is. With the rear floor mats up, can you hear the pump running?

What makes you sure that you have a fuel supply problem? Dry spark plugs?

This could be a bad CPS maybe?
 

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2006 CLK 350
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Discussion Starter #5 (Edited)
When the car started the fuel pressure was measured around 30 psi. The pressure held when turned off. I released the pressure and attempted to restart and the pressure was zero. No voltage with the key in the on position.

Just checked....Fuse 10 Good. No voltage at fuel pump with key in the on position.

Which relay is for the fuel pump?

Just put in a new upgraded crank position sensor.
 

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2004 CLK 240 Coupe
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Just checked....Fuse 10 Good. No voltage at fuel pump with key in the on position.
Which relay is for the fuel pump?
Just put in a new upgraded crank position sensor.
OK

1. I thought you were advised to check rear SAM fuse f4 (15A)
2. I told you how to find relay A in the W209 forum stickies. As you are a newbie, the drawing you need is provided below.
3. What is an 'upgraded' CPS?

Please now complete your profile with User CP at the top of screen ^^^, as model/year/location often helps with answers here.
 

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2006 CLK 350
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Discussion Starter #8 (Edited)
Rodney, Fuse 4 is ok.


Here is Relay "A"

Is there a test procedure for these?


Crank Position Sensor was upgraded from part #004-153 to new part 642-905-00-00.

Thanks!
 

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Apply 12v to the coil leads, then check continuity on the switch leads.
 

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2006 CLK 350
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Discussion Starter #10 (Edited)
Applied 12 volts to the relay. The relay clicked and continuity was OK.

When the car cranks I smell fuel.

Going to recheck voltage at pump when cranking and key in on position.
 

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2004 CLK 240 Coupe
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You could do a couple of thing here: - but you neeed a helper.

1. Check the condition of the relay output contacts, if possible. They should not be pitted/burned, as that would affect the resistance of the pump circuit. If bad, replace the relay. If OK then,

2. Put the relay back into the socket with the cover removed. Now operate the coil manually by pressing on the end of the coil with something insulated, so that the output contacts close. Hold that position.

Now try a start with the ignition switch. If that works, the problem is not with your fuel supply system.
 

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Discussion Starter #12 (Edited)
Thanks for the info.....I jumped the relay pins and had the same voltage at pump connector. Could not hear the pump run.

The car has been sitting so the battery is going to get a long slow charge tomorrow.

Received a Star Service CD for the car and slowly reading up.

Also have a nice fuel pressure gauge testing kit on the way from E-bay so I can always monitor the fuel pressure while testing.

Going to double check everything and make sure the problem before buying the pump.

Maybe the relay.

Thanks for all the input. Will post the conclusion to this repair.
 

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2004 CLK 240 Coupe
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OK - if you think that the relay N10/2 kA is good, go now to the pump connections on the tank. Disconnect the existing cable. The input wire colors for the pump motor are Brown (which goes to chassis) and Black/Brown (+12v dc)

Use a multimeter to check the resistance of the motor. Not sure what is should be - but not infinity! Now apply 12v dc (linked from your battery) directly to the pump terminals on the tank. You should be able to hear if it is spinning.:thumbsup:
 

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2006 CLK 350
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Discussion Starter #14
Resistance 125.5 Ohms on pump leads.

Put 12.8 volts on the wires from external power source. Pump did not run.

Looks like the pump. Going to check the Benz Dealer to see if there is a recall on my gas tank.
 

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2004 CLK 240 Coupe
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I see that you're in California. You may be in luck here, IF the original sale was there. Not as a 'recall' but with a permanent warranty! :)
 

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2006 CLK 350
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Discussion Starter #16
The issue is the fuel pump on passenger side. Pulled out and transferred nozzle from the old pump to the new. There is a tab on the nozzle. Push the tab in in to remove. Snaps right on the new pump without any effort.
 

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Good news - so does that mean that this problem is now solved?

I have to say that this original statement of yours was a tad misleading. "When the car cranks I smell fuel". If the pump was toast, it's hard to know where this fuel was coming from...:confused:

I hope that you replaced the O ring on the feed line.
 

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2006 CLK 350
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Discussion Starter #18
When I was attempting to start there was still fuel in the rail. The pump is toast. What I should have done was snap off the line to the pump instead of removing the clamp. The fuel line is a complete assembly. The car is not running yet...almost there.
 

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Discussion Starter #19 (Edited)
The car is repaired. Replaced pump on passenger side of tank. Car fired right up after adding fuel to gas tank. Thank you for the feedback.
 
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