SL/R129: How to test distributors and rotors - M119
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Joined: Jul 2008
Posts: 213
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From: SW Florida
1995 SL500 - 2017 AMG GLC 43
How to test distributors and rotors - M119
My 1995 SL500 decided to run very rough and felt like it was only running on 4 cylinders which of course upset me. I clean my rotors and distributors with a Dremel and small jewelers file each year when I change my spark plugs. So far that has kept them in good working order. Well I figured one of them bit the dust. He's how I easily tested them to determine what had failed. With the help of one of bobterry99's Startek links, I used the test chart and my VOM to find the bad rotor and distributor. Really easy test. Just put one lead of the VOM on the spark plug wire connector and the other on the inside of the distributor as seen in the attached photos. Same with the distributor.. A good reading as seen in the chart is 700 to 1300 ohms. As you see in the photos, one is good and one is bad along with the rotor. I ordered two new Bosch distributors and rotors and now the engine is happy again. And I know for sure one was bad.
