300SL engine problem
 

Hi All,

I was driving on the highway this morning when the car suddenly hesitated on acceleration before the engine dies off. I called my mechanis and he checked the fuel pump and it is in working condition. He suspected there is no spark. However while waiting for the two truck, about an hour, we try cranking the engine again and it starts and move like nothing happen. We are puzzle and the car is still in the workshop as I'm scared to drive just in case it happen again. Any thoughts is highly appreciated.

Thank you.

Sounds like either the Overvoltage Protection Relay (common problem especially around a 1990 model year) or the fuel pump relay. Just because the pump is in working order does not mean it is working when the engine quits.
Gilly

Thanks. I will inform my mechanic to check the OVP relay. At the moment he has done anything to the car but I'm not driving it since I'm scared that it will stop again.

Thanks for the response.

See "To all shade tree mechanics" by RickyD. This may help. Sounds like you have the same problem.
Pete S

300 SL (1989)
and others.

Hi All,

Shared all the info to my mechanic but he decided to just change the spark plug. So far so good but I still think that I need to consider changing some item suggested.

Thank you all.

Relay locations
 

For:
Gillybenztech is:
Dan Gillitzer
Mercedes-Benz Master Technician
ASE Master Technician
Zimbrick European
Madison, WI
Dan - could you please give me the exact location OV and fuel pump relays. I'd like to carry spares. Part #s would be nice also. I carry a jumper wire for the fuel pump relay plug on my 300CE but I don't have the shop manual for the SL. Thanks, Craig

On the 90 300SL, there is no independent fuel pump relay. They have a MAS (engine systems) control module instead. The MAS and overvoltage protection relay are located under the black plastic cover near the right (passenger side) hood hinge.
The MAS is easy to spot, it has a black plastic wing nut looking latch with I and O cut into the metal shield, with indicates the direction to turn the knob to unlatch the module.
The OVP is in this same general area, it is identifiable by the clear plastic window on the top of the relay with the 10 amp fuse or fuses under the window.
Gilly

Relay location
 

Gill - thanks for the information. Craig