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Old 09-15-2002, 05:06 PM
Posts: n/a
Black Soot from 1973 450SL

I have been fighting this problem for sometime. When the car is cold and is started, I get a big cough of wet black soot from the exhaust pipe. This leaves black 10" dia. rings on my drive way. I have replaced the plugs, points, Spark Plug wires and water temp. sensor. I have cleaned the injection points, removed the injectors and pressure flushed them with cleaner (no long term leakage). All vac. hoses appear ok. The pressure sensor appears ok. (I could not blow or suck through the intake vac. connection) Timing is around 12 BTC degrees, no vac. Cylinder compression is even at 170-180 psi. Fuel line ring pressure is set at 29-30 psi and is stable with no long term leakage problems.

After the spit of black soot at startup, the car runs well ( for one with 184K miles) Mileage sucks though, I am lucky to get 8-9 MPG.

I have heard that I could scope the injector pulses and see if the pulse length is correct. Does anyone have this information ?? Steve B?????
I do have a 20 meg. dual trace scope, but no CO 2 Analyzer. I also think I can faintly smell gas in the oil. I have changed the oil after only around 400 miles. It comes out clean but smells like gas.

Hope someone can direct me in the right area.

Thanks to all,


After the car warms up, it runs well. Mileage sucks though
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