1987 300e Hard to start when warm
 

Over the past several months my 87 300e has become increasing difficult to start once the engine has warmed up. Cold starting such as over night is excellent, but once I have driven for 15 minutes or more. It requires 10 to fifteen seconds of cranking.

The car has 233,000 km, Well maintained, with the usual warts addressed.

my 1991` 300sl had the same problem and i replaced the fuel injectors which would leak into the cylinders and the car was difficult to start when warm or hot. the car would also sputter and sometimes stall. they were easy to replace and fairly inexpensive.

very common M103 problem..

chances are (from cheap to expensive)

- fuel pump check valve (~$15 at partsshop)
- over voltage protection -ovp- relay (less likely in this matter)
- fuel accumulator (next to fuel pump, ~$120)
- fuel pressure regulator (under air cleaner next to fuel distributor, >$200)

many people just give up and crank more than once when the engine is warm. in my case, i replaced the check valve and fuel accumulator, no help. considering my ovp is in good shape (no hot start problems), only item left is the fpr which costs arm&leg at the MB dealer.

The last two summers I've experienced this problem with my '91 300E. I tried something which seems to work. I start the car with the A/C compressor off. It works fine hot or cold.

I've been attributing the problem to the temperature but it appears related to the A/C compressor.

BTW, the car has always shifted hard with the A/C compressor running but just fine with it off. This problem has occurred since the car was brand new.

I can't explain any of this.