Recently, I have been noticing a rough idle and hesitation from my 85 280 GE at stop lights. Once, the car has even hesitated itself out and died, another time, I stepped on the gas, the car went, then felt like it went dead, and then went again, on and off for about 150 feet. Recently I replaced the starter, nice to know the old wrench to the side of the starter trick still works when the bad one left me stranded. However, is my current problem more representative of clogged fuel lines/filter or could it be a spark plug issue etc? I'm really trying to figure this one out on my own. I'm a bit curious because while I know that you SHOULD be able to run 87 Octane through the vehicle, when I bought the car from Capt. Spalding, he said, the car was happiest with 91, didn't fully elaborateas to why. At first I ran 91 only, however, with gas being $3.61 a gallon for 91 at my local stations and having the 25 gallon tank, $3.41 for plus(89) seemed like a fair compromise. Could the lower octane fuel combined with an older motor be the culprit?
Also, my battery light on the instrument cluster has a tendency to stay on a bit longer than the other lights, even though the car has a fairly new mercedes benz battery in it...
My 85 does/did the same when I first got it on 87 octane. I put 91 and no problems and seems to run and idle much smoother. I tend to wonder as my engine was rebuilt 30k miles ago whether that has something to do ? If I remember right your engine was rebuilt about the same mileage as well ???? I am taking mine to the shop to get a new oilfilter housing gasket put on for a viscious oil leak and am also having him do some fine tuning for the altitude here as my G mostly ran at sea level prior to my ownership.
One other thing, is your A/C running while this happens ? Mine seemed to idle at stoplights rougher while engaged.
Whilst it may not be faulty its worth having a look at the overvoltage control which will be under the dash with the fuses. This controls the electronics and the fuel pump. These relays are a k nown urce of failure but usually suffering dry or failed soldered joints which can be remade.
Items listed below can be inspected and repaired eaasily not in any order.
Blocked primary fuel filter next to tank.
Slow running adjustment set to to low speed. adjust to 800-900 rpm
Cold start device element failed.
Split air hoses on slow running circuit.
Dirty air filter.
Fuses corroded on fuse block needing changing and cleaning contacts.
Dirty injectors replace after new filters or use injector flush.
Fould or service expired plugs.
Poor plug leads wipe any surface dirt away with cloth wetted with cellulose thinners.
Distributer cap cracked or rotor arm If fitted black cover over brown cap cut retaining rivets and remove ripe off cap with cellulose thinners, tracking common.
Take to garage with electronic testing for Bocsh as may be a chance of sensors or board fault ( uncommon).
Check on the wires from alternator to conector on inside inner wing point of electrical corrosion which can give unsteady voltage and gremlins.
Check battery and charge condition at 14.2 volts at battery reving and 12.5 volts off after standing for 20 minutes.
In these models injectors use to have problem in low rpms . They use to loose a litlle quantitie of gasoline ( that is not sprayed) ...its normal to this see this . The principal sign is an engine trepidation in the start. It may cause dirt candles . I think thats it.Test injector, change candles....
Zé
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Fernando
Forgot that your second origional post mentioned that the charge light stayed on longer than other lights.
Thinking about that and the first post might indicate that the tick over or slow running setting was to low and the engine is running badly because of that reason.
The engines can suffer from injector problems if used a lot for short runs the injectors become fouled. As my comments and Zes the injectors are acommon fault cheap in relative price and really easy to change. If you change them dont forget to get new rubber injector inserts. One and a half hours will seee you done on this job simple spanners only needed.
My 85 does/did the same when I first got it on 87 octane. I put 91 and no problems and seems to run and idle much smoother.
It's no wonder you get these problems, since the 280 has an older engine that's most likely optimized for 91 or even higher. Here in Norway, an engine like that, and of that vintage, would be set for either 95 or 98 octane - most probably 98.
One shouldn't run the car on too low octane, since the combustion characteristics of the lower octane fuel is different enough that it can cause engine damage (if you're unlucky). If you're running the engine on lower octane fuels (but within the range the car can handle), the timing should be adjusted. I believe I saw a thread on that somewhere, but I can't remember where it was. I didn't pay too much attention, since i've got a diesel.
A guy I know has an '86 260E (W124) that's set for 98 octane, but it will run on 95. I've borrowed that car some times, when my car has been in the workshop, and you can feel the idle is the rougher and the engine doesn't run as smooth when running on 95.
The battery light staying on a little bit after you've started is perfectly normal. It means the alternator is not providing sufficient voltage, and a rough, too low idle will give this symptom. On my diesel, I will get this symptom in very cold weather - the colder it is, the longer it persists. Stepping on the accellerator while in neutral and depressing it a short while will get the alternator up to speed.
Oh - about the gas price... Try $7.18/gallon for a change That's why the diesels are so much more attractive here in Europe, and why small cars are so much more common. Try comparing for instance the VW Tourans 5.8L/100km with the G500s 21.8L/100km. I'm frankly surprised to see so many G-wagons on the roads here in Norway.
That's why the diesels are so much more attractive here in Europe, and why small cars are so much more common. Try comparing for instance the VW Tourans 5.8L/100km with the G500s 21.8L/100km. I'm frankly surprised to see so many G-wagons on the roads here in Norway. 
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