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  #1  
Old 09-24-2007, 04:15 PM
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Question Ignition Control Unit Test ??

I have a 84 380 SL with 165,000 miles that has been well maintained and garage kept. I'm having trouble getting it started. It is not getting any spark at the plugs or the coil wire at the distributor. I check the coil wire for resistance was okay, checked the coil, primary and secondary wiring are good. I now am suspecting the Ignition control unit.

Does anyone know if there is a wat to test the ICU?

Thanks
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  #2  
Old 09-25-2007, 09:42 AM
meltedpanda's Avatar
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when this happened to me I found a short on the condenser line out of the distributor, years of vibration caused the mount to wobble and short out. If you want you can always bypass the ICU using a conventional point set up with resistor bars
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  #3  
Old 09-25-2007, 12:39 PM
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Quote:
Originally Posted by joe380sl View Post
I have a 84 380 SL with 165,000 miles that has been well maintained and garage kept. I'm having trouble getting it started. It is not getting any spark at the plugs or the coil wire at the distributor. I check the coil wire for resistance was okay, checked the coil, primary and secondary wiring are good. I now am suspecting the Ignition control unit.

Does anyone know if there is a wat to test the ICU?

Thanks
The equipment to bench-test an ICU is quite sophisticated. The only way I know for the home mechanic to test it is on the car. Can you try it on someone else's (running) car?
There is an outfit in FL (www.4mercedes.com) that will test your ICU for a fee which they subsequently credit towards a rebuild, if it's needed.
Careful before you declare your coil ok by resistance testing the windings. Mine tested good that way, but turned out to be dud anyway. Coils are a lot cheaper than ICUs.
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  #4  
Old 09-25-2007, 02:51 PM
meltedpanda's Avatar
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what is the part number?, I have several lying about
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Ron
2011 Porsche Cayman - Bond,James Bond
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #5  
Old 09-25-2007, 03:26 PM
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According to AllData, you need to replace the switching unit if:

- there is anything other than 0 volts between pins 4 and 5 of the diagnostic socket

- dwell, measured at pin 1 of the diagnostic socket is > 23 degrees
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  #6  
Old 09-25-2007, 04:27 PM
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Thanks for all the useful info. I'm in the Phoenix area, but don't know anyone in the area that I could test the unit (and coil for that matter). I don't want to just replace parts, I'd like to find the source of the problem.

Thanks again.
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  #7  
Old 09-25-2007, 04:37 PM
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Melted,

I'm not at home right now, but I'll publish the part number when I get back.

Thanks.
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