Hello!
I have a beautiful 1987 560SL. My husband and I bought it about 17 years ago and lovingly refer to her as our mid-life crisis car. Truth be told, we’re a bit past “mid” life now and have decided to sell it and let someone else enjoy her. Last summer she started to have an annoying issue and we “thought” it was fixed, but right after I started advertising, she started acting up again.
The engine simply dies while driving. It always seems to happen when I’ve only driven about 5 miles and going rather slow - 20 to 30 mph. She’ll start back up after a try or 2 and be fine. We took her to a local shop and the mechanic said one fuel pump was shot and the other was not working properly so we replaced both and all seemed fine the rest of the summer. We garage her for the winter as we live in the Rockies and she’s not the most practical car to be driving in the snow and ice. This summer she started right up and was doing well until a few weeks ago - same problem. Any thoughts or suggestions, please?! We live in a rather remote area, no Mercedes dealers within 250 miles and the mechanic we used last year seems to have closed shop.
Thanking you in advance for your help.
If the engine simply dies suddenly, it’s more likely an electrical problem. Often this is a symptom of a bad iginition switch, or a loose batter cable connection. I’d first clean and tighten all the battery cables and the ground connection to the chassis. Then I’d look at the ignition switch. Then all the other electrical connections and parts: coil, distributor, etc.
You might also post this on a MB SL forum, the SL owners are a pretty enthusiastic bunch. It’s 25 years old, so imagine yourself in 1975, seeing a 1950 car drive by…
The 560SL is the best of that model, so you should be able to get a good price, once you get this problem fixed.
I just checked on Ebaymotors, looks like nice ones get bid to about $10,000, pristine ones to $20,000, with a lot of high miles ones in the $5,000-$7,000 range.
I have a similar story with a 1995 SL500. I also decided to sell the car and it immediately began to act up. I have taken it to several mechanics and thought it was cured but not so. It doesn’t quit peacefully while driving but will cruise along beautifully for about 15 miles (and it doesn’t necessarily heat up in that time) and will begin choking, coughing, backfiring and spitting out smoke until it finally stalls, usually in a very dangerous location such as an intersection. If I wait around 10 minutes it will start up again and purr along for another 15 miles. The most recent attempt at a cure was a new cam sensor which actually seemed to work but after 100 miles of smooth sailing we are back to the 15 mile intervals. The other odd thing is that the last mechanic let it idle for 2 hours as a test and it ran smoothly.
This car has had plenty of attention and plenty of rides on the back of a tow truck. It has a new wiring harness, new transmission, new fuel pump and other repairs too numerous to list. I hate to give up on it but I also hate to see a good mechanic cry.
Any suggestions out there?
Agreed that the OP’s problems are likely electrical in nature and finding the root cause could be very difficult if not near impossible.
I think Mercedes, like other European cars, started using wire harnesses back around this time period that were biodegradeable and designed that way.
A 1985 SAAB I used to own started suffering a few problems involving starting and running and for which there was no apparent answer. After a lot of grief, I discovered the main harness was disentegrating.
The only way I discovered this was by taking a razor blade and slicing open the insulating sheath for the harness.
The insulation covering the individual wires was cracked and crumbling like day old toast which was then leading to wire to wire contact, intermittents, and so on.
Hm. If it’s not electrical, I wonder if the tank is not venting properly. That might have killed both original fuel pumps as they were already worn and having to work that hard against the improper venting was too much for them.
OP, I suggest you take the gas cap off and drive it around for awhile. If the stalling stops, your fuel tank is not venting properly.
I was a Benz tech at a dealer for many years and I’m familiar with your car.
Those 560SL cars were NOTORIOUS for failed fuel pump relays. They’re located behind the glove box relay, by the way. We used to unplug the relay and bridge the connection with banana plugs.
You pros will know what I mean.
The ignition coils often failed after the engine was running for awhile. I suspect a bad connection “opened up” when the coil got warmed up.
I suggest you bring the car to a shop that specializes in Benz and other european cars.
There you will find an old school, competent mechanic to help you out.
Nothing against the younger guys, but I’ve found that patience comes with age. And you have to have patience, because you have to diagnose it systematically, which takes time. A lot of the younger guys will only see an old car that might be harder to diagnose.
If your car does need parts, I HIGHLY suggest only Mercedes-Benz brand parts. I’ve had many bad problems with aftermarket parts, even German aftermarket parts.
The “biodegradable” harnesses were introduced after this car was out of production. They showed up in the 90s. Of course, this car’s harness is pretty old by now. But those harnesses I was referring to even failed under warranty, or soon thereafter.
@db4690, thank you for the info. I’m not a Benz guy so I wasn’t for sure when that wiring problem started. My '85 SAAB wiring was pretty much a disgrace but the '83 is fine so the mid 80s seemed to be the point where SAAB, and possibly Volvo, went downhill.