99 Jimmy 4dr 4.3 V6 150k,
A week ago I replaced the SCPI unit with MFI and fixed my hard starting issue. Today the truck started up but would not stay on felt like it was starving for fuel. I checked fuel pressure with ignition in ON position and read zero. I can hear the pump come on but with a grinding/spitting kinda noise. My question is why am I getting a zero reading? the fuel pump seems to be working enough to get the truck started. Thanks for reading.

 

If the pump makes noise, it doesn't necessarily mean it's building pressure. At the service port near the distributor, it should indicate 60psi to 66psi with the engine off and the fuel pump running. If not, you'll need to modify the pressure tester to connect directly to the fuel filter outlet. All fuel pressure and flow must end at the tester. With the pump running, pressure must be 73psi to 108psi, and it must remain above 55psi for at least 10 minutes after the pump shuts off. The results of this test will determine where the problem is.

 

Failed fuel pressure test @ fuel filter outlet. Replaced fuel pump with Delphi unit and fixed the problem. I took a risk and purchased from Amazon like i did with the MFI unit hope these last.... Thanks Capitan!

 

cool. at least now you got a new pump and spider. Other then fixing a leaking lower manifold gasket (itll happen,trust me lol) your blazer should be set for a long time.