hello again....i have another question about my 93 mercedes 190 e thats sometimes wont start. well today i went to the store and my car wont start again, but this time i notice something, if i keep turning the key off and on i can hear the fuel pump humming a little still no start. but when the pump gets louder after turning the key off and on a few times it will start, only when the pump gets louder, i check the fuel pump relay it look good i jump pin 1 and 2 the pump works what type of problem it might be. a fpr thats looks good but bad, or bad fuel pump my next step is the mechanic shop.

If you can check the fuel pump pressure, but it sound more like you may be fuel pressure regulator, thats the item that maintains pressure in the system after you shut it off. When that bleed down you have to build the pressure back up. The fuel pumps only run for a few seconds after you first turn the key on, then stop, the difference in sound maybe the amount of pressure building up. IN MHO.

Isnt a bad fuel accumulator a symptom in warm start problems?

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Yes it is but it is also to hold pressure isnt it?

Bad accumulators cause a long crank in these, worse on cold start. Does the car crank when it is a no start? I see a lot of ign switches go bad in these, circuit 50 failures.

First of all check the gas tank, if it is empty then "humming" sound is obvious. If gas is enough then i can say that usually it is the fuel filter that's clogged and causing strain on the pump. Replace the fuel filter first (if possible) and see if the noise comes back or not.

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