Can someone tell me what triggers the injectors on a 1999 blazer. I have good fuel coming from the pump but none going in the motor

 

How do you know what the pump is doing? You have a Fuel Pressure Regulator then to injectors.

 

PCM fires the injectors by applying ground to them.
Have you checked fuel pressure and leakdown with a gauge?
Have you tried spraying carb cleaner in the throttle body and see if it starts?
Fuel pressure regulator is after the injectors.

 

Bart, don't go crazy changing the fuel pump and all that stuff. Start with starting fluid in the throtle like Captain Hook suggested--it should start for a few seconds at least. The PCM or computer sends the signal to the injectors when/if it receives all necessary signals. Keep in mind too that the security system also cuts off the fuel delivery if it's not working (I'm having that problem now). The blazer has a complicated fuel system and it can be a nightmare for most hobyists. See if your security light on the dash stays on or is completely off for a clue. In my case, it's not and there are other tell tale signs like: the lights inside dont turn on when I open the doors, the alarm doesn't turn on or locks and unlocks the door; and I even noticed that the battery is draining. This brings me to the Body Control Module which controls everything I mentioned especially the fuel injector signals. If it starts with starting fluid in the throttle body, check the fuel pressure and go from there. Good luck!


WARNING:
There is a 'Hook" in this posting. The Captain didn't mention where the Fuel pressure regulator is located. That's where the unreal fun starts!

 

Its not a hard job at all to replace the regulator. It just takes a bit of time.

 

Just to clarify, (and elaborate) The regulator is attached to the injector housing inside the plenum, and it's not difficult to access at all. When the fuel pump is activated, it delivers 73psi to 108psi of fuel pressure. The pressurized fuel travels from the pump to the fuel filter, through the fuel line past the service port, across the injectors, into the regulator, (arrow on left) and fills the area on the front side of the diaphragm inside the regulator. The regulator is located downstream of the injectors so the fuel pump can supply and maintain fuel pressure and volume to the injectors when the engine is under load.



Here's how it works: Spring pressure on the back side of the diaphragm keeps the valve plate closed which allows the system to build pressure. The amount of spring pressure on the valve plate determines the regulated fuel pressure, which should be between 60psi & 66psi. The higher the spring pressure, the higher the fuel pressure is. When fuel pressure on the front side of the diaphragm overcomes the spring pressure on the back side of the diaphragm, the valve plate opens and directs the excess pressurized fuel back to the fuel tank through the fuel return line, (arrow on top). Fuel pressure then decreases until the spring pressure overcomes the fuel pressure on the front side of the diaphragm. The port labeled “vacuum connection” does not have a hose connected to it on CMFI or CSFI fuel systems. It is exposed to manifold absolute pressure inside the plenum. When idling or decelerating, the port is exposed to high vacuum which pulls on the back side of the diaphragm decreasing spring tension on the valve plate, which causes fuel pressure to decrease. As engine load increases, (cruising or accelerating) the port is exposed to low or zero vacuum which increases spring tension on the valve plate which causes fuel pressure to increase. The highest regulated pressure is obtained when the engine is off, (zero vacuum in the plenum) and the fuel pump is running, that's when fuel pressure is tested.