Hello, new to the forum. Have a 2003 V40 with around 125k miles. A few issues have surfaced, the worst being long starts. It'll crank over for a while before finally starting. But after having started it'll start back up pretty easily until it's sat for a while. Figured it was the fuel pump and was recommended that by a mechanic so I've replaced that. Didn't help. Also not sure if this is related but when idling sometimes it almost seems like it wants to die, like it's not getting enough fuel or something. Might be related?

 

fuel pressure regulator is the likely cause. Easy fix but an expensive $200 part.

 

1) Check the fuel pump. After switching ignition on the pump should sound for a couple of seconds,-then stop.

2)Remove the rubber hose going from the fuel pressure regulator to the intake manifold. No gas should be present, it should not even smell of gas.
If there's gas or it smells of gas the diaphragm has ruptured.

3) Find the schrader-valve located on the left side of the fuel-rail. Remove the plastic cover and depress the valve needle. Gas should squirt out. Then you at least know that there's pressure but not how much. You'd need a gauge for this. You could buy a cheap tire foot operated pump and make a gauge from the parts from the pump. Very easy and quick project.

If you suspect fuel related problems checking fuel rail pressure is a must.