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1999 SLK230 Kompressor
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Discussion Starter · #1 ·
It died on her way back from work, would not start again.

It will crank but will not turn over. She said it has been cranking more on start up like a fuel filter problem.

I have it at the house, If I put carb cleaner in the breather tube it starts for just a second.

Any suggestions? I can hear the pump prime when the key is turned!

I need to know how to check something fuel related, is there a fuel relay?

Thanks in advance,
Anthony
 

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1999 SLK230 Kompressor
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17 Posts
Discussion Starter · #3 ·
No codes, it started after @ 12 hrs the first time, I drove it @ 5 miles and brought it back, Now will not start period, just cranks.

cranks strong, and when I squirt a little carb cleaner is starts right up then dies.

Has to be fuel starved correct? Is there a fuse or module/relay that will stop fuel flow?
 

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SLK 230 Kompressor 1998
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366 Posts
Not an expert but, could be a K40 relay issue (search it in the forums)
Could be battery???
Sometimes there are certain codes in the system without a check engine light.

My theory, if you waited 12 hours and then it started, that could mean bad battery.

I have had a battery issue once, I knew the battery was low on juice, I left it disconnected overnight in order to stop discharge and allow recovery, then the next day I started it and drove it to charge battery a little and buy some time till I get replacement.
 

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1998 SLK 230 K
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70 Posts
No codes, it started after @ 12 hrs the first time, I drove it @ 5 miles and brought it back, Now will not start period, just cranks.

cranks strong, and when I squirt a little carb cleaner is starts right up then dies.

Has to be fuel starved correct? Is there a fuse or module/relay that will stop fuel flow?
If the motor cranks strong, it will rule out a batery issue, and taking into acount it actualy fires up with the carb cleaner, I suppose it has "juice" to the spark plugs.

Fuel starve is my best bet, and even though the pump primes, it may not be delivering fuel. I sugest starting with the K40 or thr fuel circuit (Pump and filter).

Wish you the best of luck.

Best regards.
 

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'01-E320 & 02-ST2
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First thing I'd do: Engine off, check for fuel under pressure at the valve on the fuel rail.

Note that if the crank sensor is failing, it will not pump fuel. That is probably the easiest and cheapest way to proceed and not an awful DIY.

Good luck.
 

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1999 SLK230 Kompressor
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Discussion Starter · #8 ·
Ok checked the fuel rail===NO pressure or fuel going into.

Relay? pump? I don't think it is the filter but am willing to change it.

I can hear the pump prime I believe--Is there anything that cuts it off before it goes to fuel rail??
 

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'01-E320 & 02-ST2
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Ok checked the fuel rail===NO pressure or fuel going into.

Relay? pump? I don't think it is the filter but am willing to change it.

I can hear the pump prime I believe--Is there anything that cuts it off before it goes to fuel rail??
Yep. If the Crank Position Sensor is not sending proper data for a start cycle the ECU cuts off the pump.

If you're going to DIY, I'd change the CPS. That's pretty inexpensive and easy enough to do, and cheaper than anything else you can do at this point. And if you're over 75,000 miles the thing is suspect anyway. ;)

The K40 relay is another good suspect, too. You can check all of the solder connections on it for free, just be sure to disconnect the battery before you start messing with it. :eek:

Understand I'm not guaranteeing it is the CPS. But it's a solid candidate, and if I owned your car that is exactly how I would proceed.

Good luck.
 

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1999 slk 230
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cps

Yep. If the Crank Position Sensor is not sending proper data for a start cycle the ECU cuts off the pump.

If you're going to DIY, I'd change the CPS. That's pretty inexpensive and easy enough to do, and cheaper than anything else you can do at this point. And if you're over 75,000 miles the thing is suspect anyway. ;)

The K40 relay is another good suspect, too. You can check all of the solder connections on it for free, just be sure to disconnect the battery before you start messing with it. :eek:

Understand I'm not guaranteeing it is the CPS. But it's a solid candidate, and if I owned your car that is exactly how I would proceed.

Good luck.
If the CPS is dead would there be spark at the spark plug?
if it is fuel starvation wouldnt that be fuel pump issue?
 

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'01-E320 & 02-ST2
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If the CPS is dead would there be spark at the spark plug?
if it is fuel starvation wouldnt that be fuel pump issue?
The problem with the CPS on the M112 and M113 is that they typically fail intermittently. Most cars when they die they are done, and that's it. The initial post about it dying and then starting later sounded like the typical stuff.

It can work intermittently, so it can send garbage data to the ECU, but the coils can still fire. There's no fuel pressure, so it tries to run with starting fluid, but ether will fire on almost anything.

These kind of things are hair-pullingly frustrating. There is a laundry list of possibilities, but I'm approaching it from the perspective of a DIYer. If I had to pay someone to work on it, I would probably approach it differently. However, the CPS is like $40-55 online (depending on the clip count) and a basic DIY -- and the things fail in that 80K miles + range with some regularity. The only thing cheaper than that is the K40 relay if the solder joints are failing, and that can be checked for free, and that's also a viable starting point. You can also hook up 12V direct to the fuel pump, which would tell you if the pump is working.

As I say, there are lots of approaches. I'm just tossing out ideas based on (1) my experience and (2) reading way too many threads like this one, both here and on other MB forums.
 

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Bad CPS will kill spark and fuel pulse. It should not kill the fuel pump itself. You should still get pressure at the rail. If you get no pressure at the rail during crank or initial key on, your pump is bad. The pump motor can run but not be pumping anything through it.

Because it will start and run on spray (carb cleaner/starter fluid/wd40), I would suggest you access the fuel pump and try to run 12v to it. See if it a. is physically working, and b. check the fuel pressure at the rail (if the pump is running). If no pressure but pump runs, remove the fuel filter and run the pump with 12V to see if any fuel is coming out the lines. If no fuel, replace pump.
 

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2004 230SLK
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If you can hear the pump run when you switch on the car and you have no or low fuel pressure at the rail you probably have a bad pump. I had this happen to me and the fuel pressure was very low after the car was warmed up. The fact that the car will fire if you give it a shot of cleaner means everything is working OK ignition-wise.
 
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