Good Day

This car has a very difficult to trace intermittent problem of cutting out occasionally---usually on a downhill. Not electrical since there are no observed dash lights function drop offs (rev-counter etc)----and all symptoms point to fuel prpblems. Engine has been checked for fuel pump electrical integrity amongst other things--the pump and it's controller electrics were replaced two years back.

Now the car will not run. It occasionally starts and runs for a few minutes---then cuts out. after much trying to restart it then eventually fires and the engine goes backwards for a turn or two combined with a large puff of smoke from the lower radiator area (I fear from the sump or front crank engine oil seal area). This is my homespun prognosis believing that the fuel flooded engine occasionally pre-ignites giving this phenomenon).

We can have this car towed to a Merc garage but the distance is great and the car may only need a timing module or some small thing changed.

It is very well maintained and apart from this failure runs exceptionally well--like a new car. When looked at by the Merc' people during earlier intermittent stoppages (occuring say once a month) they could find nothing wrong.

Is there something I could do or have checked on specifically and can that puff of smoke be explained? I fear too that some things like cganging fuel filters may not have been done as regularly as claimed. Would it be a god idea to change this if I have any doubts?

Car has done 100 000 miles.

Guidance will be very much appreciated

Regards

Ed

The way you describe the running backwards and smoke I tend to believe you have an ignition based backfire in the intake. Since the ignition is computer controlled it will be hard to test in the field. The one exception to this would be the cap and rotor. Definitely not the easiest, and as a result it is not often inspected during servicing. Its also well built and expensive enough not to shotgun at every service as one might on a Domestic auto.

If it is in the cap you will probably see it on disassembly. The center terminal of the cap and the rotor resistor often blow out. The rotor can short to the shaft without visable evidence though. If you go in at least replace the rotor.

I agree with Steve, check the rotor and cap. I have seen the engine try to start and kick back and the problem was solved by replacing the distributor cap. The old cap was found to be cracked and was arcing across the terminals. Thats why I will always save some old parts from a tune up like the cap and rotor in a ziplock bag for testing when I know that they worked before.

MB 300E Starting problem
 

Hello JDUB and Steve

You both responded. You were absolutely right. Distributor rotor had a chunk off it, carbon lines, cap was cracked and the fuel filter badly blocked.

Car going like a dream now.

My sincere thanks to you both.

Ed