Pagoda SL Group

W113 Pagoda SL Group => Electrical and Instruments => Topic started by: silver 250 on May 07, 2016, 13:39:02

Title: 1967 250 SL ignition stays on.
Post by: silver 250 on May 07, 2016, 13:39:02

Hello
I have a 250 SL and I came home the other day and heard the fuel pump running in the garage of the SL.
I looked and saw the red light on in the dash, but the key was in the off position. I started the car to try to clear the propblem and let it run for five minutes and then tried to turn it off and it would not shut down. I played with the ignition switch and finally got the car to shut down, the fuel pump was still running and I had to disconnect the battery to make it stop.
Any insight out there as to what may be the problem????

Title: Re: 1967 250 SL ignition stays on.
Post by: Tyler S on May 07, 2016, 16:31:15

First try unplugging the voltage regulator on the rt fender well. If that fixes the issue, the alternator may have an internal short in the field winding shorted to B+. Another culprit may be the electrical portion of the ignition switch. It is difficult to access. The speedometer and possibly other components need to be removed for access.
There has been some mention about low brake fluid or a bad float in the reservoir causing the low brake fluid warning system to cause a backfeed in the system. This backfeeds power to the switched side of the ignition switch. They can be isolated by un-plugging the 2 electrical connectors on the brake master cylinder reservoir.

Title: Re: 1967 250 SL ignition stays on.
Post by: mbzse on May 07, 2016, 19:13:16

Quote from: silver 250

.../....the fuel pump running in the garage of the SL. I looked and saw the red light on in the dash, but the key was in the off position.../...Any insight out there as to what may be the problem?

You can read about this well-known but puzzling phenomen in our Wiki, here:
http://www.sl113.org/wiki/Brake/LowFluidWarningLight (http://www.sl113.org/wiki/Brake/LowFluidWarningLight)
/Hans S

Title: Re: 1967 250 SL ignition stays on.
Post by: silver 250 on May 07, 2016, 20:13:43

Thank you for your input, unfortunately the reservoir has no float nor any electrical connections. I unpluged the voltage regulator on the right fender and still the fuel pump kicks on.

Title: Re: 1967 250 SL ignition stays on.
Post by: silver 250 on May 07, 2016, 21:01:00

To clarify I have a european model 250 sl 1967

Title: Re: 1967 250 SL ignition stays on.
Post by: mbzse on May 10, 2016, 09:10:39

Quote from: silver 250

To clarify I have a european model 250 sl 1967

Yes, with a serial No higher than 2980 I presume. These cars were equipped with two floats and electrical connection to the brake fluid container; and used the middle of the three light positions in the Kombi instrument as "low brake fluid level" warning (and door ajar warning).
Early production 250SL as well as 230SL had an empty lamp position in the middle.
/Hans S

Title: Re: 1967 250 SL ignition stays on.
Post by: ctaylor738 on May 22, 2016, 18:42:22

Could someone have wired a relay to run the fuel pump? 

Title: Re: 1967 250 SL ignition stays on.
Post by: Paul & Dolly on May 23, 2016, 07:25:10

Could the problem not lie with the electrical connections at the back of the ignition  key switch ?

Good luck

Paul