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Discussion Starter #1
I'm having trouble with my 2000 slk 230. It ran perfect when i first bought it about 2 years ago. About 3 months ago it began to run kind of rough and the check engine light came on. I researched it and determined that it was the k40 relay. I bought a new one and replaced it instead of repairing the old one(which was burnt and I still have).It started a couple of times but ran even worse. But now it won't start at all. The engine light is off now but it seems like it's not getting any gas. I poured some gas into the throttle body and it started up but as soon as that gas burned it begin to sputter and cough and then it died. It won't start back unless I add gas to the throttle body. I am a female and I don't know much about cars but I can learn. Your help would be greatly appreciated. Oh yea....it has gas in it(lol).
 

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Hi and welcome to the forum, from a very chilly UK.

I read this forum thread only the other day, talking about the K40 relay, and how the actual PCB the relay sits on sometimes deteriorates and requires re soldering..

The first line goes "Early SLKs suffered from soldered joint failures on the K40 pcb. This mainly affects smooth op and fuel pump."

perhaps have a read of this, and see if the symptoms you have seem similar. They certainly sound similar to me.
 

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Discussion Starter #3
The K40 relay WAS bad. It has been replaced with a NEW one. The check engine light went off after it was installed but now it seems to not be getting fuel into the injection system. I was thinking maybe it's the fuel pressure or maybe something as simple as a fuel filter being clogged. At this point my car doesn't start at all without being primed at the throttle body and then it dies after the fuel is consumed.
 

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Sadly Woolly has passed away
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Welcome from what was a beautiful top down day in NE England. When you said you changed the K40 relay, did you actually check the PCB that it plugs into? The relay itself is rarely a problem, it's the solder pads on the board that need re-soldering. The initial flow soldering system used was not up to the current being passed through the joints, and they'd over heat, crystalise and you'd end up with a bad/intermittent/dry joints. Simply re-soldering them properly can cure a multitude of sins.
 

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Discussion Starter #5
I changed the entire component, not the relay itself. It was brand new from a respected dealer of OEM parts. I opened the old one and sure enough one of the joints was burned. So i'm keeping that one as a replacement if the new one ever goes bad.
 

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Sadly Woolly has passed away
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I changed the entire component, not the relay itself. It was brand new from a respected dealer of OEM parts. I opened the old one and sure enough one of the joints was burned. So i'm keeping that one as a replacement if the new one ever goes bad.
Have you rechecked the new one to ensure that hasn't burnt out again?
 

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Well we'll have to have another think about it then if you changed the whole PCB as in the picture below, and not just the relay unit.

I suppose it will be a process of elimination, starting with the cheapest component first...

At least this way you might get a load of new components fitted to your car, or if your lucky, just 1... lol

 

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Premium Member 2002 SLK230K
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Welcome from New Hampshire. Since you have the old K40 re solder the bad joints and put it back in the car and see if it runs any better. At this point you have nothing to lose.
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Discussion Starter #14
Thank you guys for a very warm welcome. I appreciate it. I have just repaired my old K40 relay but the problem still exists. Any other suggestions?
 

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Hi from London, it's a top down afternoon, Nice! :tu:
sorry to hear about your problems, can't help, but i hope you get it sorted soon!
 

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Welcome to the forum from southern california.

Based on your symptoms, sounds like fuel starvation to me. With the replacement K40 board and the the repaired original K40 board still giving you the same symptoms I would recommend checking/changing the fuel filter, fuel pressure regulator and/or the fuel pump. Knowing the fuel pressures and whether the fuel pump is actually running would help to narrow down the problem. Given that your car won't even idle without manually adding gas, I think your fuel pump isnt running. Check the 5 fuses on the K40 board, if they are good (I forget which of the 5 is for the fuel pump), check if your fuel pump is running.

This post has pics which show the 5 15 amp (blue) fuses. One of those 5 15 amp fuses is for the fuel pump:

http://www.slkworld.com/slk-r170-general-discussion/1030-k40-relay-module.html#post12358
 

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Welcome from Michigan.....
 
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