380SL going bonkers...please help - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 04-16-2008, 01:30 AM Thread Starter
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380SL going bonkers...please help

Hi all.

I just spent my last $3K on an '81 380SL (128K mi) 2 days ago. Needed a daily driver but this may not be it. I've had a '69 280SE and a '75 300D.. both were bullet proof and reliable. Are these 107 SL's less-reliable/higher maintanence? All kinds of issues are popping up...on a Benz with 128K mi?

Anyway, the car won't START now. It ran consistently and smooth but It had a high idle (around 1100RPM starting and then 1600RPM after warm-up). So, after checking the Over-Voltage Relay fuse, testing for current in the Idle Control Unit, I finally pulled off the Idle Speed Adjuster (or Idle Control Valve) to clean inside it & perhaps loosen the piston. I tested it with a car battery and it did click repetitively.

I was curious as to what idle the car would be at with the Idle Control Valve completely absent....so I tried to start the car without it. No turn over at all.

I then reinstalled the cleaned Idle Control Valve and then attempted to start the car again......with no success. The only difference now was that the Idle Control Valve is clean and I put hose clamps on the pipes connecting to it because they were loose fitting. Nothing else different.

So what happened?

Did I get air into in the injection system because I tried to start it without that part installed? I tried to start the car for 20 minutes straight afterward with my foot to the floor. If that's the issue, is there an easy way to bleed the system or is it auto-bleeding by cranking it for 20 minutes?

!!!!!!!!!!!!..............My new SL is dead.

By the way, I'm still not sure what was causing high idle.... vacuum lines look OK but I' not certain (car was sitting intermittenly for 4 years). Idle Control Unit does send some voltage (because the RPM's changed when I pulled the plug off Idle Control Valve...which it's connected to right?). I even pulled the oil temp switch and no RPM change occured...so it's not that. Also..there was a strange clicking sound coming from around the Idle Control Unit - in the dash. Maybe a relay of some kind? Is there a relay in the engine computer box in the dash? - because it sounds/feels like it's coming from there.

Well at least the car looks good. So far it's about as bonkers as a Maserati Biturbo I had a few years ago. But I will try to keep hope alive.

Thanks for any help!


Last edited by Chris_Ginsburg; 04-16-2008 at 01:45 AM.
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post #2 of 3 (permalink) Old 04-16-2008, 11:39 PM Thread Starter
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Thanks for all your feedback! I couldn't have figured it out without you all.........You're a godsend.

It turns out that the new Costco battery I bought was 50amps less than Benz spec and while it cranked the engine fast and strong, it didn't juice the fuel pump.

When I put jumpstart cables on the battery......the car fired right up immediately.

I guess the original fuel pump (128Kmi on it) needs a big kick in the ass to run.

It's funny that when a car, any car, mysteriously won't start it's usually the damn fuel pump... huh?
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post #3 of 3 (permalink) Old 04-17-2008, 10:03 AM
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only mercedes and a few others use fuel pumps
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