Sometimes Does Not Start

I have a 1998 CLK320 with 69,000 miles. Recently, while driving and slowing to a stop or when the car is idling, it will stall and not start right away. If left alone for 30 minutes or so, it will start. It also seems to have a rougher idle but smooths out above idle rpms. I changed the fuel filter but the problem continues. There is no check engine light on. Anyone have any ideas or suggestions? Thank you.

What exactly do you mean when you say it won't start right away.

Does it turn over (spin) freely? Or is it acting like the battery doesn't have enough juice to turn it over?

First off, check out your battery. Make sure that the battery can pass a load test. This is critical .... just because the car turns over does not mean the battery is good. Make sure to test it.

Then, I'd check fuel pump relay --- it's located in the trunk next to the fuse box.

See picture.


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Then checkout fuel pressure.

Let us know how you do.

If all that checks out ok.

Check your crankshaft position sensor.

located just before the transmission.

See pic.


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Thank you SL600 CRUZIN. The battery is strong and turns over the engine well. I'll check out the fuel pump relay and crankshaft position sensor as you suggest. I'll let you know how it goes. Thanks again.

Well, I just replaced the fuel pump relay. But it still quit running when I pulled into the driveway. I'll check out the crankshaft position sensor next. Hope that's it.

I had a similar problem. It was the oxygen sensor that needed to be replaced. It was realtively cheap. Its as good as new now.

02 sensor will "usually" throw a code and the "Check Engine" light will come on.


Crankshaft Position Sensor is a pretty common problem (as are the early fuel pump relays) which will have the above mentioned symptoms.

And "usually" the Crankshaft Position Sensor will not throw a code (No Check Engine Light).

Thank you both for your input. I'll try checking the crankshaft position sensor next, then go from there. Thanks again.