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Registered
1986 Aust. spec 420SEL, U1700L Unimog ex.ADF
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80 Posts
Discussion Starter #1
Hi all,

Just wondering, is it normal for an ICV to buzz loudly (and to the touch) when ignition is on but car not running?

I’m guessing it is, but I don’t know.

Trying to work out if it has anything to do with my “hard” starts (2-6 seconds of cranking).

Whole fuel system has been reco’d:
Pumps
Filter
Accum
Press reg
Injectors

The CSV seems to get power sometimes, others not. (Still not 100% about it too)
 

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Registered
1985 MB 500sel (Euro)
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148 Posts
Interesting question. For what it is worth, my car is also a slow starter and always has been. I put a Gen II ICU into it which allows for a short pump priming before ignition and it improved cranking slightly, but I think your 86 is already a Gen II.

On the Idle Control Valve (ICV) I just tried it with the ignition on and engine not running. dead silence. If however you remove it from the harness and apply 12 volts (quickly) across the prongs it will hum or click, meaning it works.

Somewhere in this forum is somebody who might be able to be more helpful.
 

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Registered
1991 560sec. 1969 280SL
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971 Posts
Don’t know about your car but on mine if the ignition is on with engine off the idle control valve buzzes.
 

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Registered
1985 MB 500sel (Euro)
Joined
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148 Posts
tried it again. silent at the IACV. what I do get is a short buzz at dash while the warning lights are checking and blinking off. ?? somebody will chime in with an answer. hopefully.
 

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420SE
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345 Posts
My 420 has always done that. I just presumed it was normal.
 

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Registered
1985 MB 500sel (Euro)
Joined
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148 Posts
I don't know why none of the excellent savants who know things are not jumping into this. Have talked with my excellent mechanic who assures me buzzing with key turned on but not motor is not the usual. I guess as long as it works, buzz or no buzz is fine.
 
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