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  #1  
Old 08-02-2005, 08:02 AM
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Question 97 S420 Cranks but won't Start

Hi,

My 97 S420 (140) has lotsa battery and starter cranking power but won't fire.

I drove to work on Friday all was fine. Went out to start it to drive home and it wouldn't start.

Added gas, (just to be sure).

Pulled and tested the Fuel pump relay, its good.

I have a lot of experience with my 1990 126 coupe, but virtually none with this newly acquired S420, it has only 45K miles and all else seems to work fine. I've had it 6 weeks and this is the first hint of problem.

Before I just tow it to the dealer I thought I might try this post.

I haven't even located the spark plugs on this engine yet so I can't test for fire at the plugs, but I suspect thats next.

or check for voltage at the fuel pump, Where is the pump on this car?

fortunately this car is parked at work and is no problem.

Any ideas?

rogerben

90 126 coupe 127K
97 140 sedan 45K
2004 E500 4matic wagon 15K (hers)
and a 2004 F250 Diesel to tow the broken Mercedes home with.

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  #2  
Old 08-02-2005, 08:10 AM
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Location: Tucker, Ga USA
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FIRST suggestion is trying a different KEY. ON the 1997 & later cars the KEY must return info to the round ring around the ignition switch. IF the key has been dropped OR just doesn't return that signal the engine won't start!

CODE in the engine computer would be P1 570.
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  #3  
Old 08-02-2005, 09:14 AM
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It worked!!!

I had an old key in my desk, and I tried that, and it didn't work, but when I went back to the original key this time it started.

But I need to know more about this "Key". My 1997 key is nothing remarkable and not electronic like the 2004 E500. So I am surprised it worked.

(also I replaced the fuel pump relay with the same old original unit that I had earlier pulled and tested.)
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  #4  
Old 08-02-2005, 05:17 PM
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The 1997 & later cars ARE equipped with DAS (drivers auth system) the ring around the ignition switch sends signal into the key & the key MUST return correct signal OR the DAS locks out the fuel computer.


The batteries in the key have NOTHING to do with the transponder signal!
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ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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  #5  
Old 08-30-2013, 12:30 PM
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mbdoc, please help.

I'm having a similar issue, but I only have the one key. The housing was cracked and falling apart, so I changed it with a new shell from ebay. There was an led attached to the board inside the key and that broke off. Could that be my issue? Everything else works(buttons, flip key, etc) the engine turns over but won't start. I replaced a coil pack and the FPR, but still won't start. If I put gas in the intake it fires until that gas is gone.

Broken Key? If so that sucks, how much are they?
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  #6  
Old 09-20-2013, 02:52 PM
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i paid $260 for a dealer key for my w140 and w126
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  #7  
Old 11-03-2013, 08:43 AM
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Not a Key

I have a 98 S420, same issue, but starts. If it were a key the car would not crank. I've been thru that issue with a different benz so have other friends. I also notice my power is not up to par. Takes putting the pedal nearly to the floor for it to take off with authority. Plugs, fuel system OK. I'm leaning toward cam sensing? Anyone with experience on this? It would explain both the prolonged cranking to start, and the lack of power.
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  #8  
Old 11-03-2013, 09:00 AM
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I've heard the cam would give a bad idle,have you scanned for codes.test fuel pressure for pump,or filter failing should be 52 psi idle and 60 psi full pedal
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  #9  
Old 11-03-2013, 09:03 AM
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a bad no start is more likely crank sensor,I heard you have to be extra carefl with the V8s as it likes to breakoff.however it should fail at warm temps of the engine
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  #10  
Old 11-03-2013, 08:30 PM
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???

Idle is good, runs OK, performance is poor. Like there is no timing advance when expected under load conditions/acceleration. When starting it cranks way too long before kicking over. Most times I press the peddle to the floor while cranking to help it kick. Thoughts?
Please reply
Thank you

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