1998 Suburban 5.7L starts but shuts off after a few seconds. Replaced the fuel injection spider, checked the fueld pressure (55psi), and still nothing. It cranks, starts momentarily and then shuts off. Before I changeed the spider it would crank but not start. Now it starts but immediately shuts off. Any ideas? Thanks in advance

Yes, it starts at 55 and increases to 60 while cranking. Once done cranking, it falls back to 55 and stays there.

You still have a fuel issue. Fuel pressure should be 56 to 63 lbs. At 56 lbs and below it would be hard to start. You need to do a dead end fuel test, witch only checks the fuel pump pressure, then a bleed down test to see if the system holds fuel pressure. Pressure should not drop more than 5 lbs in 3 minutes. If it does, you may have leaky fuel injectors or regulator since you replaced the spider lines. And the recommendation is to replace all three as a unit.

The complete fuel injection spider has been changed. That's why I'm stumped.

Thanks for the tip. I'll try that and see what happens.