Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2010 Outback 2.5 with 89K miles cranks but doesn't start. Problem has been intermittent, when it starts runs fine with no issues. First appeared in December and i had it towed to the dealer (christmas weekend) who installed a 'software update' after it started for them. ran fine until late january when it happened the night before i was leaving town. back to the dealer...no trouble codes...dealer got it started and suspected the fuel pump. put a pressure test on for four days with no bleed down but had the pump replaced anyway. about a week later it's not starting again. a P0340 appeared and i replaced the cam sensor. no luck.
there had been no recent repairs prior to this problem, came out of nowhere. no rodent damage or accidents. car had one previous owner who had all scheduled maintenance performed at the dealer. having it towed to my garage today to start chasing it down.
You have to figure out what is missing when it wont start. Fuel, spark or timing, then trouble shoot from there. Just not enough information to give you any real advice. Let us know what you find.
Unfortunately, intermittent issues are one of the most difficult problems to solve.
So, what I have done was to start the vehicle every time with a scan tool connected.
Here are some observations you can make: The following should be observed when car doesn't start:
Does tachometer move when engine is cranking?
Does scan tool indicate an engine RPM?
Does stepping on the gas pedal change the behavior of the car not starting?
Does engine starter sound strong, just like when car starts?
If an automatic transmission, move in and out of park before trying to crank engine.
Turn your alarm on and off before starting car.
But like @arbez indicates, you need fuel, spark, compression for an engine to start/run.
Now, I've only listed some things that could be done. The best situation is if the car won't start and diagnostic procedures are preformed. ScannerDanner has tons of videos on those, so I won't go into detail.
Lastly, if any of the above observations or procedures change anything, come on back to us.
For example, if you crank the car and the tachometer doesn't bounce, that MIGHT, I say MIGHT, indicate a bad crank and/or CAM sensor(s). But, not all vehicles move the tachometer during crank. But, if you are using a scan tool, it will indicate a RPM. So you can guess with one I like to rely on.
Best of luck. This type of issue just takes patience.
