99 Mustang Fuel Pressure Issue

[NateM]

I have a fuel pressure issue in a 99 mustang v6. I have replaced the fuel pump and filter twice without change in symptoms. The problem is the car starts hard (long crank before fire). Fuel pressure is at 30-40 psi when running (never an issue with running). When I finally get it started I get a puff of black smoke out the exhaust. Significant blackening of exhaust pipe noted. Fuel pressure at rail drops 1-2 minutes after shutting car off. Any suggestions of what to look at next?

 

[Zhen]

I'm wondering if you have a faulty fuel injector that's leaking fuel when the car's parked. Also, check the fuel rail pressure sensor, pressure regulator, and look for fuel leaks.

 

[madspeed]

how fast is the pressure at the rail dropping?

 

[NateM]

No leaks I can see. Difficult to fully check injectors for leaks. The pressure drops to zero in 1-2 minutes after shutting off car.

 

[NateM]

Replaced the pump and no longer drops and start right up.

 

[slow6]

hey, I think I'm having a problem with my fuel pump.
- fuel pressure with key on, no ignition; it was at 20 psi.
- fuel pressure running idle at 33 psi.
- turned car off waited 2 mins, put the key on, no ignition, and it read 40 psi. However, I left the key to on, and the pressure dropped about 1 psi a second to around 30 psi.

Is this a dying fuel pressure?

* my mustang has problems starting, with a rough start, it ignites but I have to keep the starting going until it finally starts, and then it idles rough. After I turn it off, and restart, it starts fine.