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Q: Engine turns but won't start - 2001 Mercedes-Benz ML430

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No check engine light prior to the problem. Starter is a year old from Napa replaced last year December. First the car just died at a traffic light two weeks ago and had to be towed. Since then the Goodyear mechanic has changed out the crankshaft position sensor and the fuel filter. The engine started, ran fine for a couple of days and this morning it would turn but not start. Goodyear had said next to change is the fuel pump. I am getting tired of paying for guesswork.

any ideas what the problem could be seeing there is no check engine light?

My car has 132000 miles.
My car has an automatic transmission.

A: Hello and thank you for your question. Chec...

Hello and thank you for your question. Check for the three essentials that the engine needs to run. Check for air in the engine and make sure that the air filter is not plugged up. Check for spark to the spark plugs.

If there is lots of spark on all of the spark plugs, then check for fuel pressure to the fuel rail. Check to see what the fuel pressure is with the engine off and with the engine running or cranking. If the fuel pressure is at around 15 psi to 35 psi, then the vehicle will not start.

If the fuel pressure is 44 psi to 80 psi, then the engine will start. If the pressure is low, then there could be a restriction in the fuel line or the fuel pump may need to be replaced.

If the fuel pressure is high, then there could be a problem with the starting system or the camshaft sensor could be not functioning. Check out all the possibilities prior to buying any part and verify exactly what your vehicle needs. If you need help diagnosing the crank-but-no-start, a certified professional, like one from YourMechanic, can assist with your vehicle.

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