1999 v6 Chevy Silverado won't start

The engine won't start unless i pour gas in the throttle body. I changed out the fuel filter. I cranked the engine with the fuel filter disconnected and fuel pumped out the gas line. I disconnected the fuel line at the intake and fuel sprayed out. I checked all the fuses related to fuel in the fuse box on the driver side under the hood. Something must be shutting off the power to the injectors? Any ideas as to what and how to check it?

Is the fuel pressure is good?

Fuel pump fuse, relay, pump, regulator, and filter.

1) A simple fuel pressure test with KOEO at the schrader valve on the fuel rail would be a good start.
2) Than you can check the signals to your injectors

If the fuel pressure is much below 55psi on these engines they will not start. It is hard to believe but I have seen it many times. A pressure test with a gauge should be done. After priming a couple times to get the max pressue you should have 60-66psi with the pump running and 55-60psi when the pump stops and should hold this pressure for a while. It won't hold forever but you should not see it drop down quickly.

The engine won't start unless i pour gas in the throttle body. I changed out the fuel filter. I cranked the engine with the fuel filter disconnected and fuel pumped out the gas line. I disconnected the fuel line at the intake and fuel sprayed out. I checked all the fuses related to fuel in the fuse box on the driver side under the hood. Something must be shutting off the power to the injectors? Any ideas as to what and how to check it?
Yes.
As 2 members have already said FUEL PRESSURE.

My idea would be check fuel pressure with a fuel pressure gage.

You have to have 62 lbs-up of fuel pressure cold cranking fuel pressure to squirt injector.
Do not leave home without it.

And if yuu have to replace fuel pump module replace with a delphi pump.
Airtex and othr aftermarket pumps are junk.
They have a high fail rate and some will not even have enough pressure to even start it to start with.


Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post-back fuel pressure readings.


The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.