peterarmitage
New Member
Can anyone help with my problem?
300SL24, August 1991, LHD, 5-speed Auto, bought in Oman, Middle East, no catalytic converter; model. Low mileage - 101,000km, or around 63,000 miles in 12 years and I have owned it from new. Never had any problems with it, until a year ago.
The car has had three new distributor caps in as many years. This may or may not be associated with the current problem.
The engine misfires between 1200rpm and 1800 rpm. Once outside this range, no problem (except that on tick over it also gives the occasional misfire). It is also very difficult to start, needing cranking (when cold) for up to a couple of minutes, and is reluctant to pick up; The misfire is particularly bad under anything other than the smallest throttle opening. It has become dangerous - since it is an intermittent fault, it usually lets you down when you are trying to get into a gap!!! All this happens when the gear selector is in Drive; if you go through the gearbox from 2 to 3 to 4 then to Drive, it seems to accelerate through the dead-spot without the same coughing!
MB has had five goes at fixing it, two at the main dealers in Dublin (MDL) and three times in Belfast (Isaac Agnew). Work already done includes the following:
Changed distributor cap (again!); changed all HT lead and 6 plugs; changed all injectors; changed fuel filters; fitted replacement engine/fuel management computers (on loan from MB); checked fuel injection pump pressure ok; slugged fuel tank (twice) with 4 litres of methanol to eliminate any free water; changed out petrol tank cap, which had become covered with a pink, powdery corrosion material; changed out all fuses (fuse panels in both engine and boot) - they were getting corroded and had bad contacts in some cases (warning light came on for side lights not working, even though they ok!)
Anyone had a similar problem, or can give any hints on what I could try next? My hunch is that it seems more electrical than fuel. Could it be:
· A bad earth connection between the engine block and chassis?
· Dirt in fuel?
· Faulty over-voltage protection relay?
Anyone got any ideas on fault-finding, other than keeping on changing out bits and pieces until I just happen to find the cause?
300SL24, August 1991, LHD, 5-speed Auto, bought in Oman, Middle East, no catalytic converter; model. Low mileage - 101,000km, or around 63,000 miles in 12 years and I have owned it from new. Never had any problems with it, until a year ago.
The car has had three new distributor caps in as many years. This may or may not be associated with the current problem.
The engine misfires between 1200rpm and 1800 rpm. Once outside this range, no problem (except that on tick over it also gives the occasional misfire). It is also very difficult to start, needing cranking (when cold) for up to a couple of minutes, and is reluctant to pick up; The misfire is particularly bad under anything other than the smallest throttle opening. It has become dangerous - since it is an intermittent fault, it usually lets you down when you are trying to get into a gap!!! All this happens when the gear selector is in Drive; if you go through the gearbox from 2 to 3 to 4 then to Drive, it seems to accelerate through the dead-spot without the same coughing!
MB has had five goes at fixing it, two at the main dealers in Dublin (MDL) and three times in Belfast (Isaac Agnew). Work already done includes the following:
Changed distributor cap (again!); changed all HT lead and 6 plugs; changed all injectors; changed fuel filters; fitted replacement engine/fuel management computers (on loan from MB); checked fuel injection pump pressure ok; slugged fuel tank (twice) with 4 litres of methanol to eliminate any free water; changed out petrol tank cap, which had become covered with a pink, powdery corrosion material; changed out all fuses (fuse panels in both engine and boot) - they were getting corroded and had bad contacts in some cases (warning light came on for side lights not working, even though they ok!)
Anyone had a similar problem, or can give any hints on what I could try next? My hunch is that it seems more electrical than fuel. Could it be:
· A bad earth connection between the engine block and chassis?
· Dirt in fuel?
· Faulty over-voltage protection relay?
Anyone got any ideas on fault-finding, other than keeping on changing out bits and pieces until I just happen to find the cause?
