I picked up a very nice 1994 C220 for my mom for her 80th birthday. The car had been sitting for about a year due to some electrical problems. I got the car back to my shop, charged the battery, and got it fired up. Checked the alternator output and it was about 7 volts so I replaced the alternator and the battery which would not hold a charge. I figured problem solved until I tried starting the car several days later and it cranked over fine but would not start. I checked for fuel and the pump was working fine and then checked to find it had no spark. I left the car for a couple of weeks and tried to start it again and this time the starter would not engage as if the battery was dead. Checked the battery and it was at full 12 volts. I thought maybe it was the ignition switch. I replaced the switch and the car started fine again and I figured problem solved. I tried to start the car today after it sat inside the garage for a couple of weeks and again the car turns over but will not start. I'm guessing no spark again. It's definitely an intermittent problem. My good mechanic friend suspects the crankshaft sensor. Any ideas??

Give the OVP relay a few taps and retry.
Also, cycle the key a few times and try it.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1994-Mercedes--benz-C--0-Body--Electrical&yearid=1994%40%401994&makeid=63%40%40MERCEDES%2DBENZ%40%4063%40%40MERCEDES%2DBENZ%40%40X&modelid=6321%3AMBC%7C1552%3AED%7C10000028%40%40C220&catid=241959%40%40Body+Electrical&subcatid=242003@@Overload+Relay&mode=PA

This relay is behind the plastic cover, behind the battery.

Is ABS lamp ON?

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A Dalton

Thanks Arthur! I'll check the relay (in the trunk I assume with the battery) as I've turned the key so many times it's ridiculous. And no, the ABS light is not on. And what does OVP stand for?? (new to this Mercedes jargon

OVP = Over voltage protection relay

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OK....went into the trunk and found what I'm guessing is the OVP relay. It's a green plastic relay with a fuse plugged into the top. I tapped it lightly and no difference. Car turns over great but no still no start. Should I replace that relay regardless or????

That's not it. I think that is the fuel Pump relay.

The OVP should be under the hood, passengers side, behind a black plastic panel up agaist the firewall.
It is a tall , aluminum can w/fuse on top..[ see the pic I posted]
I don't have the exact location for that mosel, so maybe some C220 owners here here does.

Do a Search for OVP in the Archieves ..top of page. You will find that relay was changed to a new syle b/c the old ones were troublesome..compare those numbers when you get it out. New=000 540 67 45. Old= 000 540 52 45
If it is the old #, change it regardless. ..and check the fuse.

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A Dalton

Thanks for all the help. I'll check it out right now and gently tap it though at times I feel like using a sledgehammer on it.

Found it Arthur right where you said it would be. Removed it, cleaned the pins and socket, checked the fuse, tapped it lightly, reinstalled, still no start. Next?????

Ok
Coul

Is it the New number?
Could well be the Crank sensor..let me look up the jumper pins for OVP.

How does the wire harness look?
Does the tach jump when you crank the starter?

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A Dalton

I'm guessing I should just replace it since it is the old number. If that isn't the problem, what would you suggest next? Is the crankshaft sensor a possible culprit though it looks like a nightmare to replace.

Like I said, old # gets replaced regardless...the orig. were INFAMOUS failure item, so we just change them and go from there.

The CPS can be checked with a meter at the plug...
Guys will tell you the car wil still run w/o OVP, but that is uncorrect on your HFM system [ full electonic] b/c the ECU needs power from OVP to do anything, including spark. Earlier models are not full electonic, so they will still run w/bad OVP.

You can also go and check for power at OVP output, but changing it anyway, [ as you should] would be the first step..my best/first bet is on the old OVP..........

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A Dalton

Thank you Arthur. I'll order one and keep you posted.

Very Good...

Post your finding , as we like follow-up remedies for the Archieves.............

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A Dalton

The new OVP relay arrived in today's mail, took 10 minutes to install and the car immediately started when I turned the key. My sincerest gratitude to Arthur Dalton for his knowledge and assistance in this matter. I have been struggling with this issue for months now, spoke with several very skilled highly regarded mechanics (and I'm not an amateur wrench), and towed the car to another garage where I was told it needed a crankshaft sensor. After a Mercedes owner friend suggested I check out this site, success. BTW, if anyone needs a brand new in the box Hella #6PU 009 110-471 crankshaft sensor, I have one. I just could not get the ambition up to change it and I would have been VERY upset to have gone through the work and find out it wasn't even the problem.

Very Good..
Now , go put those frets back on and we can jam some funk............

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A Dalton