I have a 1974-450-SLC and the fuel pump comes(for about 2-3 seconds) on each time the key is activated. then the pump shuts off. I laid under the car and listened and the pump did exactly the same thing time after time...I had just dismantled the pump and cleaned it because it had been idle for some time....it is almost like a timer is hooked to the electric fuel pump....thanks Jim

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James A. Harris

I believe pump circuit is more complex than an on/off switch. It runs for a few seconds to build pressure then stays off until the engine is running. If you want to disqualify a pump problem, hook up a voltmeter to the pump leads to make sure that electricity is cut after those first few seconds.

The fuel pump relay is energized by the main EFI relay and activated by the ECU.

Sixto
95 S420
87 300SDL

On many vehicles, the fuel pump turns on for 2-3 seconds, to pressurize the fuel rail, with the ignition key.
After that, they won't come back on until you have some oilpressure established, by cranking the engine over.
Makes sense. If you don't have oilpressure, you DON'T want fuel.

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2007 C 230 Sport.