Engine cuts out, but will start right back up
 

1985 380SE

It happens very infrequently. Although, today it did it 3 times. It seems to only happen when I am cruising along with low RPM. The engine just looses power completely. No hesitation or stumble at all. It has never lost power under load. Moisture has been discounted, as I drove it for 3 days in the rain without incident and now a week and a half later is when the problem occurs.

My first inclination says fuel pump.

Every time it has stalled, it will crank right back up and run just fine.

I also have another intermittent problem. When I start the car up, it feels like one cylinder is not firing. It accelerates just fine, but idle is rough. Turn it off and start it back up at a later time and the problem is non existant.

I think I have gremlins, what do you think?

All remarks welcome. Thanks in advance for any help!

Q

check fuel pump,fuel pump relay, fuel distributor, injectors

I had a similar problem with my 90 230E. Changed the Air filter and then ever since the engine never stalled again while cruising.

Well, it finally quit and won't start. Time to get out the DMM and the shop manuals.

FIXED!
 

Thanks for the help gentlemen. I'm glad I spent the money on those shop manuals. I was able to locate the fuel pump relay and short the socket pins 7 & 8 while brother was checking pump operation. The pump was running fine so I determined that it was more than likely the relay or wiring leading to the relay. For $75 in the FastLane, I figured it was worth a hit or miss shot to replace it. Before I ordered the part, I decided to take the cover off to see if there was a visible indication of the problem. Lo and behold, ALL THREE legs of the main relay had cracks around them where they were soldered to the board. I pulled out my trusty soldering iron and made the connections solid again. I then dropped the relay back in the fuse box and she fired right up.

This makes the second time I have experienced a cold solder joint problem on this car. The last time was the idle speed control module. Resoldering fixed it as well. The best part was that both jobs were so easy that a first time solderer could fix either problem as long as they read some instructions on how to solder to prevent errors.

I had written an article on soldering a while back and it can still be found here http://elitecaraudio.com/tips/car_audio/soldering1.shtml

Cracked solder joints in MB electronics are very very common. I don't know why, probably just that everyone drives these things forever. After all, how many Toyotas or Lexus have 300,000 miles on them after 18 years?

Re-soldering has fixed many a cruise control amp, ACC pushbutton control unit, and relay!

Peter