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Old 03-06-2007, 07:29 PM   #1 (permalink)
BenzWorld Junior Member
Date registered: Sep 2006
Vehicle: 99 SLK 230
Location: Boone, NC
Posts: 21
slk 230 won't start - HELP!!!

Hello, I think I might have this on figured out but I thought I would run it by here to double check anything I might be missing. Ideas or suggestions are welcome.

Here's the size up: I am working on a 99 SLK 230. When I go to start the car it turns but doesn't start. The k40 board was re-sodered and looks good. The only code on the OBD-II is the camshaft Position Sensor but I 've had that issue for over 7,000+ miles.

When I sit in the drivers seat and I turn the key a few positions I do not hear the fuel pump "humm" in the passenger rear side of the car. So I got under the car and examined the fuel pump. I found some corrosion on the positive rubber booted metal led. I cleaned it up and took a voltage meter and tested out the power. I took the meters postive and touched the positive wire and the neg to the metal of the frame and with the key turned I get a power reading. So when I hooked the wire power leds back up to the pump and take the fuel filter off with the gas hoses open and turn the key - I get no fuel flowing. Could this be a bad fuel pump or am I missing a relay or fuse, ETC. What else should I try before getting a new pump???

In summary/conclusion:
So far I seem to have power in the wires to the fuel pump when the key is turned but the pump doesn't humm, vibrate or allow fuel to pass through it. I think the pump must have gone bad????

Anything that you wish to add is very please feel free

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Old 03-07-2007, 04:02 AM   #2 (permalink)
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Date registered: Dec 2006
Vehicle: 1997, SLK 200
Location: Norway
Posts: 371
Considering you have electricity in the wires to the pump, and and doesn't start pumping, there is noe relay or switch problems. These would probably popped up on the OBD-II. So yes, I think it's the fuel pump. Unless anyone knows any way of testing the pump other than what you've already done.
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Old 03-07-2007, 05:03 AM   #3 (permalink)
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Date registered: Oct 2005
Vehicle: 1997 SLK 230K
Location: Ankara, Turkey
Posts: 68

1. I had a camshaft position sensor before, it puts the engine into protection mode, no supercharger etc..

2. As far as I know the humm sound comes from the PSE unit in the trunk.. so your PSE might be problematic, but I don't know if it would be related to the no start problem..

I suggest changing the camshaft Hall sensor first..
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Old 03-07-2007, 10:50 AM   #4 (permalink)
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Date registered: Apr 2005
Vehicle: Golf R32 / Prev R170 SLK
Location: Melbourne, Australia
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Remove leads from pump and put your meter on "ohms" and see if there is continuity in pump.

Without looking it up I'd guess about 100ohms?

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Old 03-07-2007, 07:40 PM   #5 (permalink)
BenzWorld Junior Member
Date registered: Sep 2006
Vehicle: 99 SLK 230
Location: Boone, NC
Posts: 21
Good point - thanks guys

Good Point leventguner,
I have always had the Camhaft position sensor trip but always been able to drive. I did a while back put a new Cam Shaft Postion Sensor in the block and it still tripped the OBD-II so I thought could it be the wiring harness or the engine computer???? (Not sure) But It drove so I let it go. I have never been able to figure out why it tripped. I am not sure if it shut the supercharger down but I am not sure if I've ever noticed it kick in like the Turbo in an old Subaru that I use to have - you could feel it give out a boost. Maybe I have all along been missing the SuperCharger - not sure - the car seems to fly like your average mercedes.

I saw the PSE unit pictures from a post on here and like the K40 soder issues. I guess I should take it out and examie it to see what condition its in. I am not sure exactly what the PSE does but I do have issues with the door locks. Sometimes they lock themselves while the car is sitting unlocked - so I always have to leave the window open if the keys in the ignition and the doors are closed. Maybe the PSE have something to do with the locks not sure. Help me understand the PSE.

Follow-up on above paragraph - in Bazzles post: (The PSE(A-37) has a vacumn pump to operate the door, boot and petrol filler locks. It also controls the alarm (if fitted) and the interior light timer, door unlock crash sensor
Plus rear demister relay and ARA control model if fitted.
It comunicates with the DAS thru the CAN from the MFC unit.)

I do have interior light timer issues and door lock problems and I might have more that I am not aware of - so I need to pull that PSE out and clean it up. I am not sure what these terms are: rear demister relay and ARA control model -- DAS, CAN and MFC unit.

Back to the fuel pump:
But I do think I have a Fuel pump issue if I power the pump with the key turned and leave the fuel filter off and there's not fuel coming out. Do you think if I had water in the fuel line and it froze due to colds temps it could have killed the pump - or does 63,000 miles do it. I got a fuel pump on order and I'll know if I am on the right track in a few days.

Bazzle - on the Ohms. So you think if I got the key turned I'll get about 100 ohms but if I have the key in my closed hand I'll have zero ohms? If theres not continuity does this mean that the digital display will bonce up and down with readings?

I know once a get a few of these tweaks sorted out I should be back on the road for spring - any other opinions are very welcome. I am open to all advice, etc.


Last edited by sealworld; 03-07-2007 at 07:54 PM.
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Old 03-07-2007, 09:11 PM   #6 (permalink)
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Vehicle: Golf R32 / Prev R170 SLK
Location: Melbourne, Australia
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Ohms is a measure of elctrical resistance of a component. Same as a set of valves in a water pipe change water flow.

The leads must be REMOVED before you check the resistance . IE: NO POWER or meter may be damaged.

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Old 03-09-2007, 03:45 AM   #7 (permalink)
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Date registered: Oct 2006
Vehicle: Two 1998 SLK230s, 2003 SLK230 SE, 2002 ML320
Location: Sydney, Australia
Posts: 919
Fuel pump resistance - disconnect both leads so there is no power or other electrical connection to the pump. If there is high resistance then it means that current won't flow through the pump motor and it won't operate. Solution, replace the pump.

Second on the camsgaft hall effect sensor. There is a huge difference in engine performance with and without it working. Even failed, the car seems to go alright but has no pep and seems reluctant to accelerate. Mine had a failure mode when the engine warmed up, and it worked when the engine was cold. Failed sensor will throw up trouble codes. Reset codes first then drive (once you have the car working) and then check for fresh codes.

“The difference between genius and idiocy? Genius has its limits." - TWS
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Old 03-09-2007, 06:17 PM   #8 (permalink)
BenzWorld Junior Member
Date registered: Sep 2006
Vehicle: 99 SLK 230
Location: Boone, NC
Posts: 21
closer but still need some hep

I am back - I put a new fuel pump on but the new pump does nothing. It has to be further up the power line or something. With new pump connected and I leave the out part of the pump disconnected from the filter side and I go to start the car (1, 2, 3 position of the ingnition) and nothing comes of of the fuel line - just a drip drop.

The tank is full of fuel

Possible problems I can factor:

1. Could there be a blockage from the tank to the pump. - with or without the key turned the pump has a slow drip if the out going line is not connected.

2. Going down to the pump the pumps connecte the tank side of the fuel line and to the power leads but its quiet and no vibrating (not sure whats normal) and dry when key is turned in any position. Could the power not be flowing? - I do get some power reading but I am not sure what to look for. What controls the power in the fuel pump wires - could it be coming from where the otherside of the fuel powers wire source - On my other cars when you turn the key in a different position the fuel pump activates. So I would think it has to be what activates it - maybe a lead or plug in the computer box under the hood passanger side front had come undone.

3. On the filter side I could see it being clogged but its not connected I am looking for fuel on the exiting pump side.

I am beginging to think its a power issue instead of a bad pump. If I could follow the lines up to where they come out under front side of the car or if I knew what to look for in the wire power.
What would you try to do - a replay or fuse or something a wiring connection - I can't locate the immediate location to check for flaws

Thx again,

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