Author Topic: The mysteries of spark-less-ness (123Ignition install)  (Read 1830 times)

K-Jet

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The mysteries of spark-less-ness (123Ignition install)
« on: March 12, 2023, 18:33:53 »
Good afternoon!

For those that don’t know, here’s the backstory. I am renewing a 1971 280SE California car (named Beverly...Hills that is. Movie stars...etc. If you're my age, you probably understand)  that sat in my German neighbor’s carport for ten years. While I’m building a 2.8 motor, I am working with the 2.5 replacement motor that he installed shortly after he bought the car.

Since I’ve owned it, the car has always had electrical / ignition reliability problems https://www.sl113.org/forums/index.php?topic=35865.msg261904#msg261904, with the engine randomly dying for what seems to me like no reason, but there is a reason. In the process of tracking down causes I have, over the months

1) replaced the alternator with a new Bosch unit.

2) replaced the spark plug wires with new Beru wires, then switched back. Both sets are on hand.

3) replaced the battery positive cable and starter wiring harness with used items in better condition.

4) replaced the Bosch silver coil with a Bosch blue coil with a 123ignition black coil. All three are on hand.

5) Reworked the transmission linkage and neutral safety switch to give reliable operation.

6. Most recently replaced the coil and distributor and ignition amplifier / resistors / wiring harness with a 123ignition distributor and coil, with new rotor and cap.

And now it sits in my garage with
- a solid 12 volts from the red/black wire from fuse 2 to the coil (confirmed with meter)
- 12 volts to the starter through the red/purple wire (Starter cranks energetically!)
- 12 volts to the 123ignition distributor connected to the + and - coil terminals (as shown in the installation book, green LED comes on when correctly positioned)
- Coil (and distributor) grounded per factory installation with the ground pigtail to the coil mounting bracket. Confirmed good ground with meter.

And no spark. No spark from the coil to the distributor, no spark from the distributor to the plug wires (checked both with a timing light and an ignition probe and a spark plug installed to the wire connector)

The coils get quite hot, but don’t spark.
- 123ignition coil 1.5 ohms
- Bosch coils are each 0.5 ohms
- Coil to distributor wires from each of the two wire sets both ~ 0 ohms.
- Plug wire sets 1k ohm and 6k ohm

I have been through the setup with two friends more knowledgable than I with no progress. I (we!) don’t understand how this can be. What are we missing?

Can I scream now?
« Last Edit: March 15, 2023, 19:26:27 by K-Jet »
Dru
_____
1971 280SE "Beverly"
1990 250D 5-speed "Opa"
1995 E220T Sportline "Sport Kombi"
1980 911SC Targa "Petrol"

Kevkeller

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Re: The mysteries of spark-less-ness
« Reply #1 on: March 12, 2023, 23:47:46 »
If the coil is getting hot is it being powered ALL the time?  If it was it wouldn’t be able to make a spark then.
1970 280 SL

K-Jet

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Re: The mysteries of spark-less-ness
« Reply #2 on: March 13, 2023, 16:39:58 »
Wiring problem. Entirely my fault. Unlike the Mercedes setup, the negative coil pole is NOT grounded to the body for a 123Ignition distributor. Just like it shows in their setup manual. Just like their customer support people just told me.

Time for a drive, maybe.
Dru
_____
1971 280SE "Beverly"
1990 250D 5-speed "Opa"
1995 E220T Sportline "Sport Kombi"
1980 911SC Targa "Petrol"

lpeterssen

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Re: The mysteries of spark-less-ness
« Reply #3 on: March 14, 2023, 13:54:49 »
Congratulations Kjet for your discovery, enjoy driving….

Negative post on any coil setup is the triggering or activation signal port.  It can NEVER continually grounded to chassis.   That port gets on a standard ignition point setup the pulsing negative signal from the cable coming out from ignition point.  And on an electronic distributor, that signal is generated at the right moment by the 123electronic distributor.

Best regards
L.peterssen

K-Jet

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Re: The mysteries of spark-less-ness
« Reply #4 on: March 15, 2023, 19:25:55 »
Excellent, helpful information. Thank you. It's good to learn stuff.

So how does the standard Mercedes setup work? The negative coil post is grounded with the ignition amplifier.
Dru
_____
1971 280SE "Beverly"
1990 250D 5-speed "Opa"
1995 E220T Sportline "Sport Kombi"
1980 911SC Targa "Petrol"