I’m new here so sorry for format,
I purchased a 2007 s40 for very little the guy I got it from has a tow truck and recovery business , the car was stolen but most importantly it ran when it was stolen. It sat for a long time and whenever I got it it looked like very little had been messed with, it has around 130k miles. They only tried to jump it with no success. I pressed on the fuel rail valve and it shoots it out with pressure, I put a new battery in checked engine bay fuses, replaced camshaft sensor , crank sensor, and vvt solenoid, the timing belt is as tight as can be I checked recalls all have been done, it’s not an immobilizer issue. It has half a tank of gas, I checked spark plugs didn’t see any oil or water. I added oil since it was nearly empty. I have not checked compression because I don’t have the tool I’m sure I could borrow one tho. The car did have a leaky sunroof and there was a bit of water in the car I’m not sure if that would affect the electronics. I can crank it and it won’t catch but after a minute of cranking I can feel a rhythmic thump, and I can smell gas in the exhaust. One thing I noticed is the flap that Controls the air intake attempts to close more and it makes a buzzing noise, im not sure if the flat is suppose to be open to let air in. I should be able to use a scanner soon to read the codes, but im still trying for now. My question now is have a been placing too much faith in the battery ? Should I jump it just incase, I know I will need to soon but would it give it more umph? Only a check engine light is on inside

 

It could be the battery causing the problem. Jump-starting might help. Also, if you hear a rhythmic thump after trying to start and smell gas in the exhaust, it might mean there's some fuel delivery but not enough spark.
Plus, I'd suggest checking for corrosion or water damage in connectors and wires. Use electrical contact cleaner if needed.

The buzzing noise from the air intake flap and its attempt to close might mean there's a problem with the intake system's control mechanism. A stuck flap could mess up airflow and affect how the engine works. Look for anything blocking the intake system or causing mechanical issues.

When you can scan for codes, it'll give more clues. And if you can, test the compression too.

 

From watching another video of someone cranking an s40 the buzzing from the flap is normal and isn't stuck. \

I jumped it today with my Dodge charger and it made a difference but it didn't start but the rhythmic thump turned to thumps as I could hear the other cylinder trying but no success I measured the battery voltage before starting and it was around 12.5-12.6v, I also returned the old vvt solenoid and crank sensor as I compared them to the new ones and found no difference the only one I left new was the camshaft sensor which gave a reading of 11v instead of 12v like the new one.

Im not sure how volvos work but when I turn the key to the third position it continues cranking on its own until it stops or I turn the key back. during its attempt at cranking it'll reach a point where it slows down and I don't feel the thumps as much, around this time the check engine light turns off and my fuel level goes back to 0 this could just be programming since the car didnt turn on but again I'm not familiar

Could this just be a starter issue? its definitely in my budget to replace but I wanted 100% certainly since I definitely hear the car cranking, but there is a bit of space between the cranks it sounds almost like a diesel cold starting but this is the 2.4i gas version lol

 

I should be able to update with codes from a reader tomorrow in the meantime I took a video of the cranking, Ive looked and not found video with a car sounding like mine on crank lol, any help is appreciated though
the link to the video is

 

I got the codes today
P0100 or mass air flow sensor
P0110 intake air temperature sensor
i have the mass air flow sensor disconnected since I have the hose unplugged from the air box and I’m not sure if the intake air temperature has anything to do with it not starting

the guy I bought it from said it has a camshaft position sensor code but I since replaced that, it would make sense for it to go away.

the scanner I have does live data but my car isn’t supported so I couldn’t check that

I think I might just be getting a weak spark, I haven’t checked all of them spark because I just kept seeing that not all of them fail at the same time, but i think I hear combustion.

I’ll go out and get some new ones and jump the battery see if that’ll get me somewhere, maybe it will since before I replaced camshaft sensor I don’t think I was getting spark

I don’t think there’s a need for me to check compression since the car was running before it sat and the timing belt seems fine.

I’ll update whenever I replace those, hopefully next time I post it’ll be running 😂