Hello, I have a 1990 Volvo 740 with a B230F 4 cyl engine. Lately it has been not starting unless I dab it with some starting fluid in the intake snoot. After that, it starts, with difficulty, and then recovers. I am wondering if it would be the fuel pump or the check valve. It did start this morning cold but it took a while. It wouldn't start after sitting all when I was at work. What do you think? Thanks-Andrew