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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53469
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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My 2007 MB S550 will not start. The engine cranks but

Customer Question

My 2007 MB S550 will not start. The engine cranks but apparently the fuel pump will sometimes fail to engage to deliver fuel to the engine.
What could be wrong ... the computer does not indicate a problem.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is***** has been tried or tested so far? Are you a technician at a shop?

Customer: replied 1 year ago.
Everything has been tried at the dealership and they have twice stated that the problem was solved and it was not....
Expert:  Marty replied 1 year ago.

Do you have any specific details for me to go on? Do you know specifically what they have tried?

Customer: replied 1 year ago.
I have trouble filling up the gas tank with fuel as the automatic shut-off is preventing constant fueling.
Could the Vapor Charcoal Canister or the Canister Purge Valve be the problem the car sometimes
fails to start???i
Expert:  Marty replied 1 year ago.

Those items will cause difficulty filling the tank and could cause a no start under certain conditions. They would mainly cause a problem right after filling the tank. The shop will need to determine if there is fuel pressure in the lines and spark to the spark plugs when the car will not start. Once they determine that they can focus on the specific system. A faulty crankshaft sensor can cause no spark to the spark plugs and a faulty engine control unit or fuel pump could cause lack of fuel pressure.