What would cause an ignition rotor to fail in this manner? Car has ran smooth following the upgrade from the 2.6 to the 3 liter. Brand new Beru non-resistor plugs were installed less than 600 miles ago. I developed a slight rough idle yesterday, checked everything and found the hose to the iacv was somewhat loose, so I sealed it up. Car started fine this morning, but as I was driving I lost power doing 80 mph and cruised to the shoulder. The car would not start so I had it towed. I checked the codes and got error #3 CTS. I tested the CTS against 2 others and all were within spec of the FSM, but I swapped it out anyways. Still no start. So I read someone's post on here about how they replaced their rotor because of a no start issue and the replacement worked for them so I thought, I may as well check mine, even though it was replaced in Feb of this year and sure enough this is what I found. I just put in a Bosch rotor, but I think this one is Bremi (made in Italy)??? Not sure.

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1990 190E 3.0L

that's a facet rotor, not a bremi. bremi looks like a bosch clone with a date dial molded into it.

i would check the secondary kv with a scope. looks like too much resistance in the plugs and/or wires. high kv would be the result. but it really could be just a cheap rotor and had a meltdown.

Too much heat or defective part. High resistance in plug wires can cause this via heat build up. I' d carry a spare rotor and the tools to change it. M103's are tough on caps and rotors but not that much.

Had one fail 15 years ago leaving me stranded, it burned underneath where yours is discolored. Fortunately the replacement gave no problems.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

The one that burned did look like a Bosch clone Also, last night I drove a good 60 miles into town to pick up some new plug wires and ignition rotor. Car ran beautifully. This morning as I'm getting ready to go to work, the car won't start again So I have at least 2 entire spare sets of all the ignition components. So plugs or plug wires are running too much resistance?? Well, I'll head out back and pull the plugs and wires and test them against the FSM specs. I'll be checking in on here while I'm troubleshooting to see if anyone else has anymore input and also to report my findings.

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1990 190E 3.0L

On GM HEI in the late 70's to the 90's rotors frequently burned due to bad plug wires...different manufacturer but same principle. The rotor would burn a hole in the plastic and short circuit the spark to ground through via the distributor shaft. The fix was cap, rotor and wires. A telltale was a buildup of black powder/dust under the rotor.


Good luck and please let us know what you find.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Ok, so here's my findings for the parts that are on the car, but no start:

1.Distributor cap terminal from inner to outer were at 1kΩ - 1.1kΩ (FSM is 700 - 1.3kΩ)

2.Ignition coil terminal 1 & terminal 15 was <1Ω (FSM is < 1Ω)

3.Ignition coil terminal 1 & 4 was 998 Ω (FSM is 8- 1.3kΩ)

4.Spark plug wires were 1kΩ (FSM 700 - 1.3kΩ per cable)

5. Spark plugs were 0Ω (FSM only states .8mm gap which mine were)


6. Ignition rotor from center to edge was 1kΩ (FSM is 700 - 1.3kΩ)

I just replaced the spark plug wires with brand new wires which were tested and within spec. I also replaced the ignition rotor with a brand new rotor which is within spec as well. Car started right up with the new wires and rotor. I'm at a loss how this is possible if the old ones all tested within spec. Also, the car started up fine last night and I drove about 60 miles with no issues and inly woke up to find the no start problem. As of now car seems ok, but I would still like to get to the bottom of this, though I won't touch any of the components that are on the car now as it seems ok and I can't risk it not starting again. I guess even with troubleshooting and getting passing results, throwing parts at the problem seemed to correct it, but I'm skeptical. What do you all think? The new wires and old wires both had about the same readings as well as the rotor.

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1990 190E 3.0L

What failure point caused the last no start, rotor?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Yes. Rotor was disintegrated and I replaced it with a Bosch rotor and all was well, but the next morning, no start again and rotor was still intact.

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1990 190E 3.0L

If it acts up again check for spark into the distributor cap and if good then out to the plugs. If none to the cap then it could be the coil. Hopefully it just runs well; but, it can be unsettling when you don't find a definitive cause.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Almost a week and no further issues. I guess I'll consider this issue resolved. Thanks for all the input.

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1990 190E 3.0L

No doubt the rotor failure was a no start issue, But once again the problem occurred right before I needed to go to work today. I pulled the rotor and cap and both are brand new and look good still, but still no start. Pulled off and tested the EZL plug per the FSM and everything is good. I tried to start again and it fired right up....instantly. Since I've already missed work again, I decided to keep it running and wiggle a few of the wires around and ended up briefly hesitating when I touched the CPS wire. I then tilted it a bit more and the car shut off. I held the wire up in that position and tried starting it and nothing. I'm hoping this is the end of it once I replace this.

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1990 190E 3.0L

I think you found something, if you can reproduce another no start coupled with zero movement/bounce of the tach while cranking a bad CPS is certain.

Good luck!!!

I put on another sensor that I had from the 124 and all seems well for the time being. Although when I looked it up I didn't see that the CPS from the 124 and 201 were interchangeable.

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1990 190E 3.0L

So, It's nearly been a year and I have not had the issue of not starting, so it was a faulty CPS (marked as L5 in the FSM 7.3-0121 troubleshooting of the KE-Jetronic).

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1990 190E 3.0L

Good catch on the no start. I used to scope them with the hood closed to hold in the heat. Same with the m112/113 engine. But that doesn't explain the burned caps and rotors that started this. You had 2 problems and assumed it was the rotors in the beginning.