Blazer has been hard to start after sitting for longer than one day for about three months. Yesterday it would not start at all.
Checked fuel pressure this morning using a jumper wire at the test terminal next to the fuel pump relay. With the pump running I have 61psi. As soon as I remove the jumper pressure dropped to 52psi. After ten minutes its at 48psi.
I checked fuel pressure at the fuel filter a few weeks ago, it was 92 psi and 62 psi after 10 minutes.

 

The fuel pump is fine. It is capable of holding sufficient pressure. If there are no external leaks between where you had the tester connected, and the fuel pressure line connection at the metering block, the problem is in the plenum. The most likely cause is an internal leak, (past the valve plate) in the fuel pressure regulator. This is a drawing of a "typical" regulator showing the parts, (it is not exactly like yours). The dark grey area is pressurized fuel:







Testing requires sealing off the return line immediately after the pump shuts off. If the pressure continues to drop, the valve plate is sealing as it should. If the pressure no longer drops, the regulator is the problem. Very important NOT to seal the return line while the pump is running, (it will most likely rupture the diaphragm in the regulator).

 

I installed a new Delphi fuel pressure regulator a couple weeks ago with no change to fuel pressure

 

We know the pump is not leaking, and assuming the regulator is good, that leaves the injector assembly

 

Will the ac delco 217-3028 work on a 2003 blazer? Rock auto only lists it for up to a 2002

 

Yes, the AC Delco 217-3028 is a direct replacement for 1996 through 2005.

 

looks like the intake has to be removed to replace these injectors

 

They can be a PITA to remove, but it's worth a try without removing the lower intake manifold, (the plenum must be removed regardless). If they won't come out, the lower manifold must be removed. If that's the case, use Felpro gasket set MS98002T, (Rock auto has them).

 

Would the fuel pressures I had cause the no start?

 

Anything below 60psi will cause driveability issues. The lower it goes, the more troubles will show up. Even with a perfectly tuned engine, when temp drops to around 20F or less, and fuel pressure is 55psi or less, you might not get it running at all.