My 2006 Volvo S40 won't sttart sfter it sits for prolonged periods of time. I had my local volvo mech look at it and he says its a compression issue. The engine only has 120000 miles on it and has been well maitained. Also how could the car run fine then quit running after it sits. Just wondering if anyone has any advice or insight. Its a 2.4i FWD model thanks

 

Maybe you have leaking fuel injectors.

What exactly is going on with compression? Is it low in a couple of cylinders, all cylinders, what is the readings across the board when cold?

 

I would be skeptical of the low compression unless I saw the numbers myself. You want all the cylinders within 10 precent of each other. And you can mess up the test if you do not have the throttle wide open.

I would suspect fuel delivery first. Let the car sit as you would when it gives you trouble. Then put a fuel pressure tester on the fuel rail. Now crank the engine and watch the pressure. It should have some residual pressure before cranking and then quickly come up to 60 psi when you turn the key to ON. The newer models like yours do not have a fuel pressure regulator, they use variable voltage on the pump to regulate pressure. There is a fuel pressure sensor in the fuel rail for feedback to the ECM.