My '02 WRX wont start up right away after i fill up with gas?

i would take your question to NASIOC.

thats your best bet if you ask me.

how long exactly does it not start for?

cuz if its like my truck, when i open up the fuel tank to put gas in it looses some of the pressure in the tank. sometimes i have to have someone try to start it while i smack the tank with a hammer cuz the fuel pump splines get all stuck together.

try having some one crank the engine and spray a bit of starter fluid if it fires up you know its your fuel pump is iffy. but i doubt thats what it is.

also what did the engine come out of. cuz ive seen a few of the 05-07 EJ255s having similar problems and it turns out the motor is blown.

did you splice the wiring harness yourself when you did the swap?

cuz it could be some screwy wiring.

This obd2 code you are talking about from the computer. That you say is the fuel cap being loose or no longer holding pressure can be a few things. Not just a bad fuel cap. Yet the fuel cap is one possible problem.

1st it can be loose or hoses that are not connected on the intake manifold. Behind the alternator and power steering pump. It's a set of pre molded hoses. There is a sensor bolted on to the manifold and a blue sensor. I used zip ties to hold them on when it fell of mine the first time.

2nd it can be the two wires under the passenger rear bumper. If one of these wires is broken it will also cause this code. I had this happen and soldered the wire back together.

3rd it could be a bad sensor or a loose hose some where. This is not as common and harder to track down.

When you turn your car off to fill up, don't just turn off the engine and leave the radio and what not on. It could drain your battery, therefore it will take a few minutes before you start it up again.

your engine is miss firing in cylinder number 2 so its either a problem with your distributor or it could be your carberator and it isnt distributing the fuel properly to the cylinder so check the inlet manifold to see if its blocked or it could be the distributor or a fault in your HT leads or the spark plug may be screwed

I used premium gasoline for my '04 impreza rather than regular and this cleared up my problem.