So for a few weeks now I have been having this warm starting problem with my 93 legacy N/A wagon (auto), when I start it in the morning it starts right up, same if it is hot and I try starting it within a few minutes of turning it off. However, when it is hot, sits for 25-30+ minutes, it cranks for about 4-5 seconds before firing up. Did a vacuum test and it didn't suggest any leaks. I have done hours of research and replaced:
the coil pack
plugs and plug wires
coolant temp sensor
PCV valve
Battery
fuel filter
fuel pressure regulator
cam position sensor
crank position sensor

injectors and rails off a parts car

Cleaned the IACV with throttle body cleaner
... And I still have the exact same problem. I can hear the fuel pump prime when I turn it to ON and once it starts it runs smooth, never misfired or stalled on me, if anyone has any suggestions they would be much appreciated!

                   
 

Edited June 21, 20178 yr by andrewtc93

Connect a fuel pressure gauge. See if the pressure drops way off after shut off when warm. You should have full pressure after fuel pump primes before start.

Check the CTS.

next time you feel certain it would fail to start properly, cycle the key to ON (not start), wait 3-4 seconds, back to OFF, to ON, wait, back to OFF, to ON, wait 3-4secs. back to OFF, then immediately try starting. Each ON cycle should fire-up the fuel pump to pressurize the system. if, as I also suspect, Subaru Scott is right, the newly pressurized system should start properly, proving that, over time, the hot/warm system is leaking-down fuel pressure.

Alright so it does seem to start better if I cycle it from ON to OFF 3-4 times before actually cranking it, would this point to a fuel pump issue? I replaced the fuel pressure regulator already but it was out of a parts car so I could just be extremely unlucky and have swapped in another bad one, do they commonly go out?

well, it points to the system losing pressure when hot, not sure WHERE it would be happening....you'd expect if it were a line/hose under the hood, you just might track it down by smell.

 

but, I suppose it could be an injector or the pump....?

I replaced the injectors and the plugs afterwards, and I did not notice any gas on the plugs so I don't think that the injectors are leaking, I'm thinking it could be the fuel pump, as I just noticed it making more audible noise than I remember. Getting the pump today and installing tomorrow hopefully this resolves this...

Got a new fuel pump and strainer in, so far so good! Starts real easy now thanks!

Must be something in the Seattle air.  My son had to replace his fuel pump last weekend.

 

Congrats on your success!