Originally Posted by MikeShields

Hi,

1991 300 SL with check engine light diagnosed to OBD 1 Socket 8 (Distributor Ignition) showing 17 flashes which on fault code table suggests Possible Cause of Failure to be "Crankshaft Position sensor faulty".

Also Socket 14 (Continuous Fuel Injection System - MAS Controller) reports 9 flashes which fault codes to "Circuit 50 failure". (note these return even after being cleared).

I'm non-mechanical but any suggestions on what to advise my non-MB mechanic to start looking at based on the above?

Thanks in advance.

Originally Posted by Mike00135

Hello,

I know its been a while you posted this but I have the exact same issue.. have you manage to find what the issue was? Any help would be appreciated.

thanks

Originally Posted by MikeShields

Sorry, nothing new to report since I have not driven the car this year (due to Covid). If you diagnose anything please let me know (and I will do the same).

Originally Posted by S_F_Taylor

I've never known of a cranskshaft position sensor to fail on a 300SL or 500SL.

You're supposed to read codes for the ignition system with the engine running. Otherwise, one consequence is that code 17 will unconditionally appear. Find more info here.

Originally Posted by chassis

@MikeShields @Mike00135 I would throw new sensors at it, starting with the crankshaft position sensor. It's a 30 year old vehicle. Nothing, including sensors, lasts forever.

Originally Posted by S_F_Taylor

You've been misled once, and with advice to replace a perfectly-working sensor you are being misled a second time. Any resistance between 650 and 1200 ohms is fine. If it ain't broken, don't fix it!

Originally Posted by S_F_Taylor

What model year is your car, Mike?

Originally Posted by S_F_Taylor

I'd check the fuel mixture. To do that you'll need a multimeter. With the engine idling at a temperature greater than 40 degrees C. you first measure the voltage between sockets #2 and #3 of the connector located on the passenger inner fender. That voltage should fluctuate several tenths of a volt and be roughly 30% - 70% of the steady voltage measured between sockets #2 and #6. Next you switch the engine off and again measure the voltage between sockets #2 and #3. Now it should be steady and be 70% of the voltage you measure between #2 and #6.

Originally Posted by S_F_Taylor

I'd check the fuel mixture. To do that you'll need a multimeter. With the engine idling at a temperature greater than 40 degrees C. you first measure the voltage between sockets #2 and #3 of the connector located on the passenger inner fender. That voltage should fluctuate several tenths of a volt and be roughly 30% - 70% of the steady voltage measured between sockets #2 and #6. Next you switch the engine off and again measure the voltage between sockets #2 and #3. Now it should be steady and be 70% of the voltage you measure between #2 and #6.