Need W108 Starting Circuit Wiring Diagram Please - Page 2 - Mercedes-Benz Forum

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post #11 of 22 (permalink) Old 06-14-2014, 10:11 AM
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Likely the ignitor unit is not working or you would have the spark assuming coil is OK.

Coil you can simply check primeryshould be 3-4 Ohm across the +and - terminal.
Secondary will be 5-6K ohm. At + and the centre high voltage terminal.
One of the components is not working.Do let know.
.
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post #12 of 22 (permalink) Old 06-14-2014, 04:34 PM
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i wished you would keep the pointes type [ standard ] ignition on the car , it is a proven system easy to diagnose.
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post #13 of 22 (permalink) Old 06-15-2014, 10:07 AM Thread Starter
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i wished you would keep the pointes type [ standard ] ignition on the car , it is a proven system easy to diagnose.
Too late now, but in hindsight that would have been better.
dws


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post #14 of 22 (permalink) Old 06-16-2014, 09:45 AM Thread Starter
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I'm not the best with electrical troubleshooting, but here is what I did:
Confirmed that new battery was up-read 12.07 volts with multimeter set to 20DCV mode.
Set meter to 20k ohms and read 8.75 across the coil + & - ignition off OR on?!
Same meter setting checked + coil to - center contact to dist .01ohm ignition on or off
These readings seem very weird to me, how can they be the same ignition on or off.....doesn't make sense.........more help, please?
dws


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1984 Mercedes 500SEC Euro (040Black/BlackLeather)
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post #15 of 22 (permalink) Old 06-16-2014, 03:20 PM
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Resistance readings with battery disconnected
Set to 20k check centre tower and + of coil readings 5 to 7 kohm.

Set to lower 2k or better aoo lower range
Test coil +. And - posts ,readings 1 to 3 ohm .
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post #16 of 22 (permalink) Old 06-17-2014, 10:58 AM Thread Starter
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Resistance readings with battery disconnected
Set to 20k check centre tower and + of coil readings 5 to 7 kohm.

Set to lower 2k or better aoo lower range
Test coil +. And - posts ,readings 1 to 3 ohm .
I disconnected the negative battery terminal, set multimeter to 20k ohm and read 8.70 + side of coil and center post.......8.70

Set meter to 200 and checked + and - coild terminals.......2.1


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post #17 of 22 (permalink) Old 06-17-2014, 05:20 PM
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Coil Primary is 2.1ohm and secondary is 8.7 kohm. So coil is operational
Seems Ignitor is not functioning,replace with points set or a Pertronix unit which would suggest
With the matching coil.

The points can have their own issue if operating through a transisterized unit,likely to be faulty so the Pertronix is the bettersolution for reliability.
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post #18 of 22 (permalink) Old 06-20-2014, 09:55 AM Thread Starter
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Originally Posted by adler View Post
Coil Primary is 2.1ohm and secondary is 8.7 kohm. So coil is operational
Seems Ignitor is not functioning,replace with points set or a Pertronix unit which would suggest
With the matching coil.

The points can have their own issue if operating through a transisterized unit,likely to be faulty so the Pertronix is the bettersolution for reliability.
I'll run through the Hot Spark troubleshooting list again and see what I get.
dws


1973 Mercedes 450SLC (PineGreen/MahoganyLeather)
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1984 Mercedes 500SEC Euro (040Black/BlackLeather)
1992 Mercedes 300SL-24 Signal Red/Black Leather
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post #19 of 22 (permalink) Old 06-20-2014, 10:06 AM
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There is usually a little wire that goes through the side of the distributor casing and connects to the points/ignitor mechanism. This wire generally passes through a rubber grommet. If this wire becomes grounded to the distributor casing it will kill the ignition. Perhaps this wire became dislodged or grounded while working on the distributor?

http://handbook.w116.org/ETM/75s.pdf

Last edited by ejboyd5; 06-20-2014 at 11:48 AM. Reason: Add schematic reference
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post #20 of 22 (permalink) Old 06-21-2014, 09:18 AM Thread Starter
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Originally Posted by ejboyd5 View Post
There is usually a little wire that goes through the side of the distributor casing and connects to the points/ignitor mechanism. This wire generally passes through a rubber grommet. If this wire becomes grounded to the distributor casing it will kill the ignition. Perhaps this wire became dislodged or grounded while working on the distributor?

http://handbook.w116.org/ETM/75s.pdf
Excellent thought, I'll give this a closer look.
dws


1973 Mercedes 450SLC (PineGreen/MahoganyLeather)
1981 Mercedes 380SL FORSALE (LtIvory/PalominoMBTex)
1984 Mercedes 500SEC Euro (040Black/BlackLeather)
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