Up until couple weeks ago the car started up and ran fine but I haven't been able to start it since. There is no combustion when I crank the engine. I have checked the following items and they all seem to be working fine

1. fuel pump - it turns on and i disconnected the hose from the outlet of the fuel filter to check and make sure that the fuel is being pumped as expected - the pressure seems to fine though i hvnt checked with a gauge yet
2. injectors - i used the mechanics stethoscope to listen for injector operating clicking sound. I can hear the clicking on all 4 injectors. I still need to check to make sure the injectors are not clogged but the reason I haven't does this yet is because it seems unlikely that all 4 injectors will get clogged all of a sudden.
3. ignition spark - removed the spark plugs and cranked the engine to check for ignition sparks. no issues here.


I also tried spraying carb. cleaner directly into the throttle body and was able to start the car for as long as the carb. cleaner was being sprayed.


I suspect the issue might be with the fuel pressure regulator though I am not 100% sure. I disconnected the fuel return hose from the FPR outlet and turned on the fuel pump and noticed that no fuel comes out even after trying to crank the engine there is no sign of fuel coming out of the return outlet of FPR. I also tried to crank the engine after disconnecting the FPR vaccum hose and applying pressure to close the hose opening, this did not work either and still no fuel came out of the return outlet of FPR.

The question I have regarding this is, should there be fuel in the return line if you only turn on the fuel pump without starting the engine?

It looks to me like the next logical step is to replace the FPR and see what happens but I wanted to run it by more experienced folks on this forum before I go buy the new fuel pressure regulator.