I have a 1991 Mercedes-Benz 300SL-24 (R129). The car has about 40,000 miles on it, but is ten years old. Of late, the car has been very difficult to start once the engine is all warmed up. After parking for twenty minutes or longer, it will require several cranks before it actually starts, and even then it misfires for a few second before idling normally. My friend's W124 300E is also experiencing the same problem.

I have replaced the spark plugs, and ignition wires. I am wondering if the ignition coil is old, since it has never been replaced.

Sounds like a fuel pressure leak down, hot soak, fuel boiling, vapor lock. Monitor your fuel pressure and suspect the accumulator (fuel pressure reservoir).

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

That makes a lot of sense. And my shed-tree mechanic was telling that it is usually the ignition coil or the ignition module.

Will have the fuel pressure checked out. Thanks.

The fuel preesure should immediately drop from 6.5 bar to around 3 bar when the key is turned off. The rest pressure should remain for an hour or more. (Usually a lot more).

The pressure is necessary to keep the fuel from boiling as it heats up standing still in the shut off system. If you are having this problem now (as opposed to when its really hot) you will find the pressure dropping to zero probably within minutes.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

According to the parts manual, there are two accumulators, one located on the in-take manifold and the other located with the fuel pump underneath the car.

I noticed that the accumulator located with the fuel pump feeds the fuel distributor, while the accumulator on the manifold leads back to the fuel tank.

I am definitely losing fuel pressure after serveral minutes. Which one should I have replaced?

Thanks for the responses.