I got the code for a slight evap leak. At first I thought it was a gas cap issue. Because it would reset on its own a couple of times. Then I got a #1 misfire code. I started to look for a problem and I found the fuel line from the low pressure fuel pump where it connects to the long fuel line going to the engine was leaking. When I went to replace the short line from the low pressure fuel pump located under the rear seat. I noticed a burnt mark on the connector to the fuel pump. I removed the pump and under the connector one of the pins was completely melted away from the other pins. I bought a new OEM pump and replaced everything. Now when I start the car up it runs bad like there's air in the fuel line. Once the car idles a bit (while giving it gas so it doesn't stall) the motor runs good. But now I have the code for multiple misfires #1, #3 and #4 cylinders. I put a pressure gauge on the low pressure fuel pump where the fuel line would go. I get 70 lbs of pressure on start up, but after a few seconds the pressure will drop. You can't see the needle move but it just keeps dropping pressure. After 10 minutes or so its down to about 20 lbs. Does anyone know if the pump should hold the pressure? I'm thinking I have a bad new pump. The fuel line is not leaking. It's a 2012 mini cooper S countryman
Thanks

 

Not clear to me but the engine is running at idle and the pressure starts out at what I assume is a good pressure, 70psi, at idle, then after the engine runs a bit -- and the fuel pump too of course -- the pressure drops to 20psi which is I take out of spec.

Bad fuel pump is possible. Did you get a factory pump or an aftermarket pump? Makes no difference I guess. Bad is bad.

But it could be a bad fuel pressure regulator assuming this is not left up to the fuel pump. A fuel line or fuel line fitting in the tank could be bad.

A tech would disconnect the fuel pump from the wiring hardness and connect 12V power to the fuel pump and confirm that it runs and that fuel pressure obtains an in spec pressure and stays there. If it doesn't then the fuel pump, fuel lines, fuel line fittings, are suspect.

 

When I try to start the car, the car will start. But it will run real rough and I have to pump the pedal a bit to keep it from stalling. Once it runs for a bit it will smooth out and run good. I disconnected the fuel line at the pump and connected the fuel gauge to see what the pressure is while turning the engine over. The pressure goes to 70 psi then after I stop cranking the engine the pressure will decrease very slowly on the gauge. I was trying to find out if the pump is supposed to hold the 70 psi after the engine shuts off. Like I said it seems like there is air in the system when trying to start the engine. The fuel line that I replaced because it was leaking is not leaking now.