Exhaust Valves Continuously Flapping When Door is Opened

[Jason29]

I recently picked up a Dark Horse and most of the time when I open the door, I hear a pumping type sound from the rear of the car for several seconds. I searched and didn’t find anything posted about it. Not sure if it’s the fuel pump priming or something else, but it seems a bit odd since it goes on for a while.. Is everyone else hearing the same thing?

Thanks in advance for your help!

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[Skye]

Yes, this is normal behavior; it's the car, priming the fuel system.

The sounds most often occur when opening the Driver's door, but can also happen when refreshing status via the Ford pass app, or when Ford and the car are talking.

The car will make several more types of sounds when the battery is disconnected and later re-connected. Any number of solenoids and relays charging back up.

 

[Zig]

Yes, this is normal behavior; it's the car, priming the fuel system.

The sounds most often occur when opening the Driver's door, but can also happen when refreshing status via the Ford pass app, or when Ford and the car are talking.

The car will make several more types of sounds when the battery is disconnected and later re-connected. Any number of solenoids and relays charging back up.

Ah man, I thought all those noises and clicking and clanking were the gremlins closing / opening up shop, just don’t get them wet and you shouldn’t have any problems type of thing

 

[Dena]

In the morning my fuel injected 96 mustang has a hum for 3-4 seconds after you first turn the key on. This is the fuel pump in the tank pressurizing the system. The fuel is pumped to the engine and there is a return line from the engine that allows any air/fuel to return to the tank. The system pretty well eliminates the old problem of vapor lock and comes in handy should you make the mistake of running out of fuel. The fuel system isn't perfect and will leak down pressure overnight but fortunately no fuel is lost in the process. This is normal and you should only worry if the pump doesn't stop running after a short period of time as that would indicate a worn fuel pump. bleeder problem or leak somewhere in the fuel system. I find the sound reassuring that the fuel system is operating correctly and the engine is ready to run. In my case, the only serving the fuel system has required after 170,000 miles is replacing the fuel filter. The system is pretty reliable.

 

[Jason29]

Thank you! This is very helpful. I have had previous Mustangs in the past that made a few clicks when you opened the door, but this seems to be running for a longer time. A check engine light came on when I drove it today, so there’s probably something going on. I’ll have to get it into the dealership to see. I’ll try to take a video of the sound showing how long it runs.

Thank you again for the assistance!

 

[Jason29]

Upon further review this morning, it’s not actually the fuel system, but the muffler valves flapping open and closed continuously for about two minutes. Then it stops. I think it still does it even after the car is started. I assume that’s triggering the CEL. Will see what the dealer can find.

 

[Dena]

Upon further review this morning, it’s not actually the fuel system, but the muffler valves flapping open and closed continuously for about two minutes. Then it stops. I think it still does it even after the car is started. I assume that’s triggering the CEL. Will see what the dealer can find.

That description sound like a position sensor might have failed and the computer has detected it. The software may try to clear it by cycling the system but after several cycles, it gives up on the process. That sounds like something that should be easy to find.

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