5.7 vortec long crank

[1990Z71Swede]

Can't answer the "just unplug" part with certainty, but If there is nothing else than injector trigger signal in that connector, then yes. Removing the Relay and draining pressure, yes but the ECU might be monitoring Voltage to the pump, at least I have seen what I believe is that in @PlayingWithTBI 's EBL logs and the Vortecs might be doing the same thing.
If it does I would Imagine it would set a code. If so, either unplug pump at the tank or since you are draining fuel anyways just run a hose into a fuel can.

 

[slow_c1500]

Would it also work to pull the 20A fuse that goes to the fuel pump relay? Or would I still need to unplug the fuel pump either way?

Also, giving it throttle didn’t seem to help

 

[slow_c1500]

Update: I haven’t tried the disabled injector test yet, but I pulled each spark plug to look at them, and #7 is slightly wet with fuel. None of the others are wet, but some have a slight fuel smell on them.

Also, the spark plug hole for #7 gave me a hissing sound again when I unscrewed the plug. This is the only cylinder that has ever done that. This is also the only cylinder that has ever given me a misfire code.

My initial thoughts are bad compression on #7, or leaky injector #7. Any thoughts?

 

[Schurkey]

Perform a cranking compression test. See what's happening.

If the injector leaks, your fuel pressure testing would show that.

 

[slow_c1500]

I tested the fuel pressure with a 150$ gauge from oriellys and it read the same as my 30$ harbor freight one. I think we can say that the fuel pressure is actually dropping and it isnt just the gauge.

So I’m thinking it could be:
-Leaky injector
-Leaky regulator (even though I just replaced both)
-Check valve

I don’t really want to pull the upper intake again but I guess I could do that, pull the injector lines out of their holes, temporarily hook up the fuel lines to the spider body, turn key on, and see if fuel comes out of any spider legs/regulator

 

[Schurkey]

-Leaky injector
-Leaky regulator (even though I just replaced both)
-Check valve

I don’t really want to pull the upper intake again but I guess I could do that, pull the injector lines out of their holes, temporarily hook up the fuel lines to the spider body, turn key on, and see if fuel comes out of any spider legs/regulator

Does your vehicle have hose in the fuel system you can access?

Run the fuel pump--perhaps on "prime", or with the fuel pump accessory wire. What ever it takes to get full fuel pressure. Then shut off the pump.

Clamp the hose coming from the pressure side of the pump. Clamp the hose on the return side of the regulator. See if the pressure still drops. If it does, it has to be an injector.

If it does not drop, the injectors aren't leaking but the regulator or the check valve (or both) could be leaking. Release one clamp, run the fuel pump to full regulated pressure, but not over 75 psi. Shut off the pump. See if the pressure drops. If you release the return side clamp, and the pressure drops excessively, the regulator leaks. If the pressure does not drop excessively, that system is OK. Then release the pressure side clamp, run the fuel pump to max pressure but not over 75 psi. Shut off the pump. See if the pressure drops excessively, if so, the check-valve leaks. If you release that clamp and the pressure does not drop, that system is OK.

 

[slow_c1500]

The vortec trucks have 3 hoses coming from the fuel pump. Which hose is which?

 

[Schurkey]

I'd expect that's in the service manual, but I haven't looked.

I was thinking that there might be hoses that connect to the intake/spider that would be easier to trace. I don't have a 350 Vortec to look at, though.

 

[slow_c1500]

There are no hoses that connect to the regulator. And the only thing leading to the spider is the 2 metal fuel lines.

I can try and get that info about the fuel line hoses from a manual or something

 

[Caman96]

Follow the hose coming from the fuel filter towards the front. There should be a rubber section.