I'm having trouble starting my 89 DOHC Si. Starts few seconds then dies. Wont start there after. Changed fuel filter, injectors, and ecu, have yet to check fuel pump and relay. My buddy shoved a gas soaked rag into the throttle body and it went for a while. So I'm thinking fuel system. Also 2 out of 3 times when I start it I get a dead battery effect (no crank). Verified fuel is coming out of injectors but maybe not enough pressure. I don't want to pay 60+ dollars for fuel pressure tester. Have access to spare parts what should I do? Please help!

 

If you think its fuel pressure - just unplug the vacuum source off the fuel pressure regulator.

 

sounds like the main relay since you said sometimes it acts like a dead battery.

that relay powers the fuel pump, starter signal, ignition, injectors

there is also a circuit in that relay that primes the fuel pump for 2 seconds, and another that runs the pump when the car starts. it could be that the pump is priming allowing the car to start for a few seconds but then the relay just isnt keeping the pump on after that.

unplugging the regulator wont do anything... the pressure is either there or its not.