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Q: Car will only start after being jumped - 1991 Mercedes-Benz 420SEL

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My car has suddenly been doing something very strange lately. It won’t start in the morning after it has been sitting all night in the garage. Every morning this week I’ve needed to get my neighbor to help me jump start my car. Once it has been jump started it runs fine all day long. But it won’t start after sitting overnight in the garage. I’ve been backing in the past few days, so it’s easier to jump start. Do you have any ideas or suggestions?

A: If this is a fuel issue, it's likely th...

If this is a fuel issue, it's likely the check-valve in the fuel pressure regulator not holding pressure during shutdown. This valve keeps a low pressure in the fuel injection system for faster starts. If faulty, the fuel pump has to run longer to build pressure back up. It may not be bleeding off pressure enough during the day to notice. A professional mechanic, like a certified technician from YourMechanic, can help diagnose and repair this problem.

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