I’ve had a 2004 Volvo s40 for less than a year and it’s already getting me into trouble. whenever I try to turn the car on it won’t, it tries to crank and it just won’t happen. Sometimes when i’m trying to crank the car i push on the gas pedal and 5/10 times it works and the car starts running fine. As well as when it is up and running it will shake tremendously before it calmes down and then it’s fine. Besides the car not wanting to crank it also leaks what i think is water right behind the passenger seat into the carpet and i have no clue as to why it does that; only happens when i use the a.c in the summer. If anyone has any tips that would help me tremendously.

 

The water leak is a plugged AC system drain - google that for the way to clear the drain tube.

I'm trying to decode your description. You seem to be saying that the engine won't crank, but then you suggest that it acts differently if you pump the gas (something that actually had an effect 40 years ago on carbureted vehicles, but won't on most modern cars). It sounds like (ignoring some of what you describe) it could be a fuel issue. Try turning the key from off to position II for a few second, then back to off to position II, and repeat a few times, and see if it now starts up correctly (indicating a fuel leak allowing the fuel rail to drain overnight).

 

common cold start issue for the Gen 1 S40s (1.9T) is the fuel pressure regulator. Symptoms would be long cranking before starting if the car's been sitting for a while (ie overnight). The FRP is on the end of the fuel rail with the fuel hose entering on top and a S shaped vaccuum hose on the bottom. If you pop off the vaccuum hose and fuel drips out, time for a new FPR... Cause is as Habbyguy noted, the FPR diaphram tears and pressure in the rail bleeds out. Cold starts will require extra time for the fuel pump to build the pressure back up...