1995 s-10 blazer 4.3 vortec wont start. have 57 psi at intake. wont fire with eather, new gm spider. advance auto fuel pump. filter.

Could be the fuel pump is not providing the proper fuel pressure !
Fuel psi less than 50 psi no start GM CPI Vortec

Problem is usually caused by the regulator in the spider head. It may not be installed correctly, not getting enough vacuum from the intake upper manifold or is failing. Start by checking the vacuum at the manifold.

Try replacing the fuel filter, but it sounds like you have a weak fuel pump. Your cold start pressure should be 62-65 psi and drop about 5 psi when the engine is running. Anything less then 62 psi is going to cause you to have starting issues, you can also test your fuel pump by blocking off the return line to see if you get 75-78 PSI. this is just a test to see if your fuel pump is still good. If you have less then that with the return line blocked off, replace your fuel pump but check your ground wire first. The ground wire is separate from the wire harness and grounded to the frame and a bad ground will give you a weak pump.
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your statement is fuel pump work ok, have you tested for proper fuel pressure. just because the fuel pump works it could have less pressure needed to start the engine. maybe the fuel filter is plugged. start out by replacing the fuel filter, if this doesn't fix it, you need to pressure test the pump. even 10 psi reduction in pressure will allow the engine not to start.

check your idle sensor. or it can be the sensor thats hooked up on your catconverter. or a pluged cat conveter

A spider injector is located underneath the intake plenum and this is multi-port. Otherwise you have a throttle body injector system. Vortec engines have spider injectors and they are super expensive to replace ($400.00- 850.00) each ! There is only one spider injector for each engine it has 6 legs/fuel tubes that go to each cylinder.

It's the check vale inside fuel pump module . Testing for failed fuel pump check valve

Check for injector pulse at the plug going into the intake. Front of intake, drivers side.

if you have done all the above go ahead and replace the fuel pressure regulator and check the intake manifold gasket for leaks if you need any GM parts you can try Schram auto and truck parts 1-800-292-1032

Hello;
First you need to have your fuel system tested. It sounds as though the relay and pump have gone out. When you turn the ignition to on the pump should energize for 2 seconds and stop. The pump will deliver fuel after startup. Poor performing pump equals poor performing vehicle. With the vehicle not staying running when it did start, I would check the fuel pressure and then replace the pump. You can check the fuel pressure regulator by pulling off the vacuum line and see if you have fuel in the line. If you do the regulator is shot. The fuel pump relay also needs to be checked for operation especially if the fuel pump is not working. Also check your rollover valve to be sure it has not tripped.
Thanks;
Rich
RPM Norhtwest